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Motor preparation and sexual action : a psychophysiological perspective on
sexual motivation
Both, S.
Publication date
2004
Link to publication
Citation for published version (APA):
Both, S. (2004). Motor preparation and sexual action : a psychophysiological perspective on
sexual motivation.
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4 4
Sexuall behavior and responsiveness to
sexuall stimuli following laboratory
inducedd sexual arousal
Abstract t
SexualSexual excitement can be seen as an action disposition. In this study sexualsexual arousal was expected to generate sexual action and to increase interestinterest and responsiveness to sexual stimuli. In two experiments, male andand female participants were exposed to a neutral or a sexual film. We measuredmeasured genital and subjective responses to the film, and sexual behaviorbehavior following the laboratory visit In Experiment 2, film exposure was followedfollowed by a task in which participants rated the sexual arousability of neutralneutral and sexual pictures. Rating time of the sexual pictures served as anan index for sexual interest. Responsiveness to the sexual pictures was measuredmeasured by modulation of spinal tendinous (T) reflexes. Sexual activity, butbut not sexual desire, was higher for participants in the sexual film conditioncondition than for participants in the neutral condition. Sexual interest and responsivenessresponsiveness to still pictures were not higher for participants in the sexualsexual film condition than for those in the neutral film condition. In
addition,addition, men who saw the neutral film showed a greater responsiveness toto still pictures than men who saw the sexual film. The results support the viewview of sexual arousal as an emotional state generating action tendenciestendencies and actual sexual behavior.
Note:Note: We thank Saskia Dijkstra, Sven Dijt, Ingrid Langedijk, Richard van
Ommeren,, and Elsbeth Reitzema for their assistance in the data-collection and data-reduction. .
Introduction n
Emotionn can be construed as fundamentally an action disposition, a tendencyy to do something (Frijda, 1986; Lang, 1993). In this view emotionss serve the satisfaction of goals and generate relevant action (suchh as fight-flight or approach). Sexual excitement, in this respect, does nott deviate from other emotions: It serves to satisfy concerns and generatess a tendency for sexual behavior (Everaerd, Laan, Both, & Spiering,, 2001). From this viewpoint it follows that sexual excitement shouldd incorporate sexual action tendencies and sexual action. To test thiss prediction, we investigated men's and women's sexual behavior followingg laboratory induced sexual excitement.
Laboratoryy studies on human sexual responses generally include measuress of genital arousal and subjective sexual arousal. Overt sexual behaviorr is seldom measured. However, sexual activity may be a relevant variablee to investigate in laboratory studies about sexual motivation. Incentivee behavior consists of appetitive and consummately responses andd generally proceeds from the appetitive phase to the consummately phasee (Pfaus, 1999). Measuring appetitive and consummatory sexual behaviorr following laboratory visits offers the opportunity to study the relationshipp between physiological sexual arousal, subjectively experiencedd sexual arousal, and overt sexual activity in men and women. Thee inclusion of measures of overt sexual behavior in laboratory studies willl provide a more complete picture of the generation of sexual action.
Incentivee motivation theories state that approach behavior will be activatedd by appropriate incentives (Agmo, 1999; Bindra, 1974; Singer & Toates,, 1987). Bindra (1974) introduced the concept of a central motive state,, "a hypothetical set of neural processes that promote goal directed actionss in relation to particular classes of incentive stimuli, for example, it promotess food seeking and eating in relation to food, or defensive fighting andd escape in relation to a predator" (p. 201). An incentive, it is supposed,, guides response selection through the excitatory or priming influencee of the central motive state on somatovisceral reactions, consummatoryy acts, and locomotor and skilled actions. Frijda (1986), in linee with Bindra, defines motivation as the elicitation of behavior systems byy appropriate external stimuli or thoughts thereof. A behavior system is describedd as a potential action (a program) or a sequence of potential
actions.. With respect to sexual responses, this means that sexual motivationn and the accompanying feeling of sexual desire arise when an individuall interacts with appropriate sexual stimuli or thoughts thereof. Thus,, in contrast to the layman's belief that sexual desire is spontaneous andd arises "out of the blue", sexual desire is the outcome of the processingg of sexual stimuli, although it may be felt and perceived as spontaneouss (Basson, 2002; Everaerd et al., 2001).
Interactionn with an incentive changes the affective state of an organism.. Bindra (1974) already pointed to the similarity of motivational andd emotional states. Action tendencies manifest themselves in various emotionall response systems, including physiological change, emotional expression,, and motivated behavior (Frijda, 1986; Lang, 1993). In addition,, incentive motivation models state that motivation is the result of thee interaction of the internal state of the organism and relevant stimuli in thee environment. The internal state of the organism, like hormonal or otherr somatic factors and past experience, modulates the responsivenesss to external cues. It may be expected that exposure to sexuall stimuli can enhance responsiveness to subsequent sexual cues byy modulating the internal state. Confrontation with a positive incentive resultss in activation of reward circuitry in the brain (Aharon et al., 2001; Kampe,, Frith, Dolan, & Frith, 2001; Schultz, 1998, 2001). Activation of rewardd circuitry may result in an increase of attention for incentive stimuli andd in an increase of subjective and physiological responses to these stimuli,, which may result in a self-amplifying motivational process.
WeWe hypothesized, following incentive motivation and emotion theory, thatt activation of the sexual system through exposure to a sexual stimuluss would generate a tendency for sexual action and enhanced attentionn for and responsiveness to sexual stimuli. Naturally, a one-to-one relationshipp between sexual arousal and overt sexual activity is not to be expected.. Rather, exposure to a sexual stimulus should activate sexual actionn tendencies, but regulation processes should affect the expression off these action tendencies. The transition of a state of genital and subjectivee arousal to the execution of sexual behavior should be mediatedd by a host of cognitive and affective processes, and the acting-outt of sexual action tendencies should be influenced by rules and opportunitiess for sexual activity (Singer & Toates, 1987).
AA number of psychophysiological studies on human sexual responsess has shown that exposure to sexual stimuli in the laboratory is ann adequate method to evoke genital responses and subjective sexual arousall in men and women (Geer & Jansen, 2000; Laan & Everaerd, 1995a).. Sexual behavior, however, is measured in only a few experimentall studies (e.g., Fisher & Byrne, 1978; Schmidt, 1975; Slob, Bax,, Hop, Rowland, & van der Werff ten Bosch, 1996). Fisher and Byrne (1978)) used erotic film and compared subjective and behavioral responsess of erotophobic and erotophilic participants. Only erotophobic participantss showed an increase in sexual behavior following exposure to eroticc film. Schmidt (1975) conducted a series of studies in which male andd female participants were exposed to erotic pictures, films, and stories.. Sexual feelings, physiological reaction during exposure to the sexuall stimuli, and sexual behavior during the 24-hour period following exposuree were measured. Both men and women showed a slight increasee in sexual behavior compared to the 24-hour period before the exposure.. In these studies, all data were based on self-report. Although subjectivee estimate of physiological reaction was included, there was no (objective)) physiological measurement of genital response. Therefore, theree was no opportunity to look at the relationship between actual genital response,, subjective sexual experience, and behavioral responses. Slob ett al.'s (1996) study on changes in sexual arousability over the menstrual cycle,, using a with in-subjects design, did include genital measures (labiumm minus temperature). They assessed women's postexperimental sexuall desire and activity after exposure to erotic videos. Women tested forr the first time in their follicular phase showed higher labium minor temperaturee in response to the film and reported increased sexual desire andd more frequent sexual fantasies during the 24 hours following the experimentall session. These data indicate that differences in sexual arousabilityy may be reflected in various components of sexual responding duringg and following a visit to the laboratory. Unfortunately, Slob et al. onlyy reported the relationship between genital response and subjective sexuall arousal, not the relationship between responses in the lab and sexuall desire and activity following the lab visit.
Heree we report on two experiments in which men and women were exposedd to a neutral or a sexual film using a between-subjects design. In bothh experiments, we measured genital (penile circumference change in
menn and vaginal pulse amplitude in women), subjective, and behavioral sexuall responses to the films. We expected the sexual film and not the neutrall film to induce genital and subjective sexual arousal. Subjective actionn tendencies were measured with the expectation that the sexual filmfilm but not the neutral film would facilitate subjectively reported approach tendencies.. We used a questionnaire to collect data on sexual desire and sexuall activity during the 24 hours after film exposure. We predicted higherr postexperimental sexual desire ratings and higher frequency of sexuall activity in participants in the sexual film condition than in participantss in the neutral film condition. In Experiment 2, in addition to postexperimentall sexual behavior, we investigated the effect of film-inducedd sexual arousal on interest in and responsiveness to sexual stimuli. .
Inn both experiments, both males and females participated to allow for genderr comparison of sexual response patterns. There is evidence for a genderr difference in sexual motivation; men seem to be more strongly motivatedd sexually compared to women (Baumeister, Catanese, & Vohs, 2001).. Baumeister et al. concluded that, across many different studies andd measures, men have been shown to have more frequent and intense sexuall desire, to fantasize more frequently about sex, to masturbate moree frequently, and to report fewer problems concerning low sexual desire.. They concluded that the evidence points to a gender difference in frequencyy of sexual desire as well as in intensity of sexual desire. We reasonedd that, if this holds true, in the present study the stronger sexual motivationn of men should be reflected in stronger sexual responses, strongerr approach tendencies, higher postexperimental sexual desire ratings,ratings, and higher frequency of sexual activity in response to the sexual film,, in men compared to women.
Experimentt 1
Method Method
Participants Participants
Participantss were 47 (25 female and 22 male) psychology students who receivedd course credit or were paid for their participation. Mean age of
thee women was 22.6 (range = 18-37 years, SD = 4.7 years), and mean agee of the men was 22.0 (range = 18-34 years, SD = 3.2 years). There wass no significant difference in age between men and women, f(43) = 0.58,, p > .1, or between stimulus conditions, f(43) = 0.92, p > .1.
Alll women had a heterosexual orientation; 16 women (64%) had a steadyy partner, and the duration of the relationships varied from 3 months too 4 years. All women but one had experienced sex with a partner and coitus.. All women practiced masturbation. Seven women (28%) had experiencedd sexual coercion at least once in their lives. All female participantss except one had seen erotic films prior to participation.
Off the male participants, 21 had a heterosexual orientation; one male participantt reported to have a mainly homosexual orientation. Since this participantt had been randomly assigned to the neutral film condition we decidedd not to remove his data. Eight men (36%) had a steady partner; durationn of the relationship varied from 3 to 8 years. All men except one hadd experienced sex with a partner and coitus. All men practiced masturbation.. None of the men reported having experienced sexual coercion,, and all men but one had previously seen erotic films.
Priorr to participation, all participants received written information includingg a description of the procedure and the genital measures. Informedd consent, in which confidentially, anonymity, and the opportunity too withdraw from the experiment without penalty were assured, was obtainedd from all participants.
Design Design
Wee used a 2 (Stimulus) x 2 (Gender) design, with stimulus and gender as between-participantss variables. Men and women were randomly assigned too the neutral or sexual stimulus condition, with the restriction of equal numberss assigned to each condition.
MaterialsMaterials and Response Measurement
StimulusStimulus materials. The two film excerpts consisted of 15-minute
videotapess with sound. The neutral stimulus was a film about zebras in Africa.. The sexual stimulus was a heterosexual erotic videotape, which wass composed of three 5-minute scenes from films, each depicting petting,, cunnilingus, and intercourse. The scenes were originating from filmss directed and produced by Candida Royalle. Films produced by
Candidaa Royalle are aimed at women and are more female-initiated and female-centeredd than conventional erotic movies. Earlier studies in our laboratoryy have shown that female-centered erotic film compared to male-centeredd erotic film evokes less shame, guilt, and aversion in womenn (Laan, Everaerd, van Bellen, & Hanewald, 1994) and that female-centeredd film elicits subjective sexual arousal and genital arousal in men (Janssen,, Everaerd, van Lunsen, & Oerlemans, 1994). In addition, Janssen,, Carpenter, and Graham (2003) reported that clips preferred by womenn elicit comparable sexual arousal ratings in male and female participants. .
PhysiologicalPhysiological recordings. In women, genital response was measured
usingg a vaginal photoplethysmograph assessing vaginal pulse amplitude (VPA),, the AC component of the signal, and vaginal blood volume (VBV), thee DC component. A signal conditioning amplifier separated the VPA fromm the VBV component using a 12 dB/octave, 0.7 Hz filter. Additional filteringg for VPA was 24 dB/octave, 0.4 Hz high-pass. Since former researchh has shown that VPA is the superior measure in terms of both convergentt and divergent validity (Laan, Everaerd, & Evers, 1995), we usedd only VPA data. The VPA signal was sampled at 100 Hz with a Keithleyy KPCI3107 A/D converter, running on a Windows 2000 PC system.. Depth of the probe and orientation of the light emitting diode weree controlled by a device (a 9 x 2 cm plate) attached to the photoplethysmograph.. Participants were instructed to insert the photoplethysmographh such that the plate touched their labia.
Genitall response in men was measured by a mechanical penile strain gaugee assessing penile circumference changes (Barlow, Becker, Leitenberg,, & Agras, 1970; Janssen et al., 1994). Changes in electrical outputt caused by expansion of the strain gauge were recorded by a continuouss DC signal. The strain gauge was positioned twothirds of the wayy down the shaft of the penis toward the base. The experimenter checkedd participants for proper placement of the device. Both the vaginal photoplethysmographh and the penile strain gauge were sterilized in a solutionn of Cidex-activated glutaraldehyde between uses (Geer, 1980).
Wee recorded genital responses continuously during baseline and stimuluss presentation. A computer program developed at our department timedd the administration of the stimulus, employed a trigger signal to
initiatee sampling of the physiological measure, and marked changeover betweenn baseline and stimulus.
SubjectiveSubjective measurements. Prior to stimulus presentation and after
thee film excerpt, we collected data on subjective sexual arousal and emotionall experience. Participants were asked to assess on a 7-point scalee their (a) overall sexual arousal, (b) strongest feeling of sexual arousal,, and (c) strongest genital sensations. The scale extremes were
notnot sexually aroused at all and very strongly sexually aroused for items a
andd b, and no sensations in my genitals and orgasm for item c. The answerr categories for men and women were slightly different: Genital sensationss were described for men as erection and for women as vaginal lubrication. .
Wee measured emotional experience by a questionnaire consisting of 211 emotions (including sexual emotions). Participants were asked to indicatee on a 7-point scale (with not at all and very strong as extremes) to whatt extent they had experienced these emotions while watching the film excerpt.. In an earlier study, factor analysis indicated that the 21 emotions couldd be divided into four factors: 7 emotions reflecting lust (Cronbach' s aa = .82), 4 emotions relating to anger (Cronbach's a = .85), 8 emotions relatingg to threat (Cronbach's a = .71), and 2 emotions reflecting tension (Cronbach'ss a = .79; Laan, Everaerd, & Evers, 1995).
Wee measured action tendencies with the Action Tendency Questionnairee (ATQ). This questionnaire, which assesses the tendency too execute overt behavior without necessarily doing so (Frijda, Kuipers, & terr Schure, 1989), was administered after the stimulus presentation. Participantss were asked to assess on 5-point Likert scales (with does not
applyapply to me and strongly applies to me as extremes) the degree to which
255 statements were applicable to them. The statements varied from those indicatingg approach tendencies (e.g., "I wanted to approach, to make contact")) to statements indicating avoidance (e.g., "I wanted to have nothingg to do with something or someone, to be bothered by it as little as possible,, to stay away"). Formerly, factor analysis revealed that the questionnairee could be divided into four subscales: approach (Cronbach's aa = .87), avoidance (Cronbach's a = .75), protection (Cronbach's a = .81),, and attention (Cronbach's a = .76; Laan & Everaerd, 1995b).
SexualSexual behavior. We measured sexual behavior with a questionnaire
withh or without coitus) during the 24 hours after exposure to the films. We gavee participants the questionnaire at the end of the experimental session,, in a sealed envelope, with the request to open it after 24 hours. Thee questionnaire consisted of seven items. The first three items on sexuall desire asked how often the participant (a) had feelings of sexual desire,, (b) had sexual fantasies or daydreams, and (c) searched for sexuall incentives. The next three items on sexual activity asked how oftenn the participant (a) masturbated, (b) had sexual intercourse, and (c) hadd sexual contact without intercourse. Participants were asked to answerr using a 4-point scale, with never and three times or more as extremes.. The last item asked whether the participant had wanted to be lesss or more often sexually active during the 24 hours. Participants were askedd to answer using a 5-point scale, with much less often and much
moremore often as extremes. Procedure Procedure
Too help participants make an informed decision about whether to participatee in this experiment, we sent them a letter in which all experimentall procedures were explained in detail. They were told that theyy would be exposed to a film excerpt possibly containing erotic material,, and they were informed about the genital measures and the sterilizingg procedures. To prevent participant awareness of the experimentall hypotheses with regard to their sexual behavior, the sexual behaviorr questionnaire was not mentioned in the letter.
Eachh participant was tested by a trained experimenter of the same sex.. On arrival at the laboratory, the participant read and signed an informedd consent form and completed a questionnaire about sexual experiencee and sexual problems. The experimenter then explained all the detailss of the experimental procedure. After the experimenter left the room,, the participant inserted the vaginal probe or attached the penile strainn gauge. After the participants signaled (using a one-way intercom system)) that the transducers had been placed, they rated their feelings of sexuall arousal and emotional experience by answering questions presentedd on the TV monitor. They answered questions by pressing buttonss corresponding with the seven answer categories. The answers weree stored in a Windows 2000 PC system.
Afterr this, a 3-minute baseline period followed. During this resting periodd participants listened to quiet music; then, the film excerpt was presented.. After watching the film excerpt, participants rated their feelings off sexual arousal and emotional experience and their action tendencies byy answering questions presented on the TV monitor.
AtAt the end of the experiment an exit interview was administered. Participantss were asked about their reactions to the experimental proceduree and the use of the genital device. After the interview, the participantss were given the questionnaire about postexperimental sexual behavior.. Since the nature of the questionnaire was not disclosed beforehand,, the participants did not know they would be asked about theirr sexual activities following the experimental session until they openedd the envelope to fill out the questionnaire.
DataData Reduction, Scoring, and Analysis
WeWe sampled VPA and penile circumference across baseline and the subsequentt stimulus presentation period. Data were entered into a computerr program developed at our laboratory, that enabled off-line graphicall inspection of the AC and DC channels. Artifacts in the VPA channell and strain gauge channels are caused by movements of the lowerr body or by voluntary or involuntary contractions of the pelvic muscles.. Since artifacts show an extreme increase in vaginal pulse amplitudee and in penile response, they can be detected by visual inspection.. After artifact removal, we averaged the VPA and strain gauge dataa over 30 seconds, which resulted in 30 data points for both VPA and penilee responses. Due to problems with the software, penile response couldd not be scored as millimeter circumference. We decided therefore to reportt the genital responses in percentage of baseline. The mean responsee during the baseline period (X) and the stimulus presentation periodd (Y) were calculated. We calculated then a percentage of baseline scoree (percentage of baseline = Y / X * 100) for film presentation.
Forr emotional experience, we averaged the items belonging to each off the described factors, thus creating a lust, anger, threat, and tension score.. For action tendency ratings, we used only the approach and avoidancee factors for further analysis. The approach items and the avoidancee items were averaged, thus creating an approach and an avoidancee score.
Forr frequency of sexual activity during the 24 hours after participa-tion,, we calculated a sexual desire and a sexual activity score. The first scoree was calculated by summing the scores on the first three items aboutt sexual desire, and the second score was calculated by summing thee scores on the items about sexual activity.
Wee tested between-subjects effects with multivariate and univariate analysiss of variance procedures using a significance level of .05. Changess in vaginal vascular responses are not comparable to changes in penilee circumference because they involve two different measures on differentt anatomical structures (Geer & Janssen, 2000). Therefore, we analyzedd genital responses for men and women separately. Genital arousall was submitted to a 2 stimulus (sex stimulus versus neutral stimulus)) ANOVA. Subjective sexual arousal, emotional experience, and actionn tendencies were submitted to 2 (Stimulus) x 2 (Gender) MANOVAs. .
Inspectionn of the postexperimental sexual behavior data revealed that regardingg sexual activity, most participants scored 0 (never sexually active)) or 1 (once sexually active). Because of the extreme non-normality off these scores, we used a statistical test for two Poisson distributions (Kalbfleischh & Sprott, 1973).
Results Results
Responsess at exit interviews indicated that participants felt comfortable duringg the experiment despite the genital measurement. There were no differencess between stimulus groups on the pretest for the questions measuringg sexual arousal and emotional experience. Likewise, there weree no differences between men and women on the pretest for sexual arousall and emotional experience. Therefore, we used raw posttest scoress for the analysis. For both men and women, we found no difference betweenn stimulus groups on the baseline measurement of genital response. .
SubjectiveSubjective Sexual Arousal, Emotional Experience, and Action Tendencies Tendencies
Duee to technical problems, data on subjective sexual arousal, emotional experience,, and action tendencies were missing for one male and one femalee subject. Mean sexual arousal, emotional experience, and action tendencyy ratings are shown in Table 1.
SubjectiveSubjective sexual arousal. The stimulus presentation had the
intendedd effect on subjective sexual arousal ratings. Ratings of participantss in the sexual stimulus group differed from ratings of participantss in the neutral stimulus group, multivariate F(3,39) = 7.52, p < .001.. There was no main effect of gender and no interaction of stimulus andd gender. Ratings were higher in the sexual stimulus group compared too the neutral stimulus group; all univariate tests appeared to be significantt (overall sexual arousal, F(1,41) = 21.88, p < .001; strongest feelingg of sexual arousal, F(1,41) = 15.87, p < .001; and strongest genital sensations,, F(1,41) = 13.18, p < .001).
EmotionalEmotional experience. We found only a stimulus main effect on
emotionall experience, multivariate F(4,38) = 6.03, p < .005. Univariate testss revealed that participants in the sexual stimulus group reported moree feelings of lust, F(1,41) = 15.75, p < .001, and less tension than participantss in the neutral stimulus group, F(1,41) = 4.17, p < .05. There was,, as expected, no effect of stimulus on feelings of anger or threat.
ActionAction tendencies. For action tendencies, the main effect of stimulus
approachedd significance, multivariate F(2,40) = 2.83, p = .07. We found a mainn effect of gender, multivariate F(2,40) = 3.84, p < .05, and no interactionn effect of gender and stimulus. Univariate tests revealed that participantss in the sexual stimulus group reported, as expected, a strongerr approach tendency compared to participants in the neutral stimuluss group, F(1,41) = 5.03, p < .05. The univariate test for avoidance tendencyy was not significant. Women reported a stronger approach tendencyy compared to men, F(1,41) = 6.86, p < .05, but there were no genderr differences in avoidance ratings. The interaction effect of gender andd stimulus on approach ratings approached significance, F(1,41) = 3.06,, p = .09. The female participants in the sexual stimulus group reportedd the strongest approach tendency. There was no interaction effectt of gender and stimulus on avoidance ratings.
Tablee 1 . Mean (SD) subjective ratings in response to neutral and sexual
filmm in Experiment 1.
Subjectivee ratings SexualSexual arousal Overalll sexual arousal3
Strongestt sexual arousal8
Strongestt genital sensations6
EmotionalEmotional experience0 Lust t Anger r Threat t Tension n ActionAction tendencies0 Approach h Avoidance/tension n Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Film m Neutral l 1.4(1.0) ) 1.6(0.8) ) 1.5(0.8) ) 1.7(1.3) ) 2.5(1.5) ) 2.11 (1.4) 1.8(1.5) ) 2.00 (0.9) 1.9(1.2) ) 1.9(0.4) ) 2.22 (0.7) 2.00 (0.6) 1.11 (0.2) 1.3(0.6) ) 1.2(0.4) ) 1.5(0.4) ) 1.6(0.5) ) 1.6(0.4) ) 1.5(0.4) ) 1.8(0.9) ) 1.7(0.7) ) 1.5(0.4) ) 1.7(1.0) ) 1.6(0.8) ) 2.33 (0.3) 2.55 (0.3) 2.44 (0.3) Sex x 3.3(1.7) ) 3.4(1.7) ) 3.4(1.7)" " 4.0(2.1) ) 4.33 (2.0) 4.22 (2.0)" 3.6(1.8) ) 3.88 (2.2) 3.77 (2.0)" 3.2(1.3) ) 3.4(1.5) ) 3.3(1.4)" " 1.2(0.3) ) 1.11 (0.3) 1.11 (0.3) 1.7(0.4) ) 1.6(0.6) ) 1.6(0.5) ) 1.5(0.6) ) 1.11 (0.3) 1.3(0.5)* * 1.6(0.4) ) 2.7(1.0) ) 2.2(1.0)* * 2.33 (0.3) 2.44 (0.5) 2.33 (0.4)
Note.Note. Statistical significance of group comparison is reported for the total groups only.. a Item response format of 1 (not sexually aroused at all) to 7 (very strongly
sexuallysexually aroused). bltem response format of 1 (no sensations in my genitals) to 7 (orgasm).(orgasm). c Item response format of 1 (nor at all) to 7 (very strong). d Item responsee format of 1 (not at all) to 5 (very strong). " Neutral versus sexual film
groupp comparison statistically significant, p < .001. * Neutral versus sexual film groupp comparison statistically significant, p < .05.
GenitalGenital Response
Duee to technical problems, genital data from one male participant were missing.. Because of problems with the newly developed vaginal photoplethysmographs,, genital data of 10 women were missing. Consequently,, we ran the analysis with 21 male participants and 15 femalee participants. The stimulus presentations had the intended effect onn genital responses (Table 2). In men as well as in women, genital responsess were higher in the sexual film group compared to the neutral filmm group, men Ff1,19) = 16.41, p < .005, women F(1,13) = 9.89, p < .01.
Tablee 2. Mean genital response (SD) to neutral and sexual film in
Experimentt 1.
Penilee circumference** Vaginall pulse amplitude
Neutral l 103.211 (11.76) 77.188 (10.17) Film m Sex x 204.10(81.89) ) 173.69(67.01) )
Note.Note. Units are percentage of baseline (response during film / baseline * 100).
"" Neutral versus sexual film group comparison statistically significant (p < .005,
dfdf = 1,19). * Neutral versus sexual film group comparison statistically significant
(p<.01,df=1,13). .
SexualSexual Behavior
Fivee women and three men did not return the postexperimental sexual behaviorr questionnaire. Consequently, we executed the analysis with 20 participantss (10 men and 10 women) in the sexual stimulus group and 20 participantss (9 men and 11 women) in the neutral stimulus group.
Theree was no effect of stimulus, gender, or stimulus by gender on the postexperimentall sexual desire score (Figure 1a). However, the mean postexperimentall sexual activity sum score of the sexual stimulus group wass .95, while the mean score of the neutral film group was .40 (Figure 1b).. The postexperimental activity score was significantly higher in the sexuall film group, z = 1.99, p < 0.05. There was no significant difference betweenn men's and women's postexperimental sexual activity scores.
Postexperimentall sexual desire (a) Dmen n DD women T T T T 1 1
T T
— — jl.6 6 - 0 . 5 5neutrall film sexual film Stimuluss Condition
Postexperimentall sexual activity (b) Dmen n DD women
neutrall film sexuall film Stimuluss Condition
Figuree 1. Mean postexperimental sexual desire (a) and sexual activity (b)
ratingss with SEM in the neutral and sexual stimulus conditions in Experimentt 1.
Thee amount of sexual activity may have been influenced by the actual or perceivedd opportunity for sexual expression. Therefore, we inspected the dataa for a difference between conditions or genders in relationship status andd the wish to have been more or less sexually active. We used Chi-squaree tests to check equality of the frequency distributions. Only the dataa of the participants that completed the sexual behavior questionnaire weree selected for these analyses.
Inn the sexual stimulus condition, 11 participants (55%) had a steady partner;; for the neutral stimulus condition this percentage was exactly the same.. Among the men, 47% had a steady partner; among the women, thee percentage was 61%. The chi-square tests revealed no significant differencee between men and women. Regarding the wish to have been lesss or more sexually active during the 24 hours following participation, theree was no significant difference between conditions. In the sexual film condition,, 63% of the participants reported that their amount of sexual activityy was exactly right, 26% reported that they had wished to be somewhatt more active sexually, and 11 % reported that they had wished too be much more active sexually. For the neutral film condition these percentagess were respectively 37%, 32%, and 32%. Similarly, there was noo significant difference between men and women in the wish to be less orr more sexually active.
Discussion Discussion
Ass expected, the sexual film and not the neutral film evoked genital responses,, feelings of sexual arousal, and feelings of lust. In addition, neitherr the sexual film nor the neutral film evoked feelings of anger or threat.. Contrary to our expectations, ratings of tension were higher in responsee to the neutral film. However, tension ratings were generally low. Wee may conclude that the films elicited a sexual versus a neutral though slightlyy tensed state.
Wee reasoned that emotions are best conceived of as action tendenciess and that sexual excitement, in this respect, does not deviate fromm other emotions. Hence, we expected that a sexual stimulus would generatee responses that prepare the organism for sexual approach behavior.. Indeed, the sexual film enhanced approach tendencies relative too the neutral film. As expected, the enhanced approach tendency from thee sexual stimulus resulted in a higher frequency of postexperimental sexuall activity in the sexual film condition. There were no differences betweenn conditions in the distributions of variables that indicated the actuall or perceived opportunity for sexual expression. We may conclude thatt the difference in sexual activity between conditions can be attributed too exposure to the sexual stimulus. It is remarkable that the elicited
sexuall action tendency was not reflected in higher postexperimental sexuall desire ratings. Participants in the sexual stimulus condition were moree active sexually after film exposure than participants in the neutral condition,, but they did not report higher frequencies of feelings of sexual desire,, sexual fantasies, or searching for sexual incentives. Thus, the elicitedd tendency for sexual action was reflected at the level of postexperimentall behavioral outcome, but not at the level of subjectively experiencedd feelings of sexual desire.
Contraryy to our expectations, the male participants did not report strongerr feelings of sexual arousal than the female participants. There weree also no gender differences in ratings of emotional experience in responsee to the erotic stimulus, and the female participants reported even higherr approach tendencies compared to the male participants. Also, theree was no gender difference in postexperimental sexual desire and activityy ratings. Although we should note that we cannot rule out the possiblee influence of gender bias in subjective report of sexual behavior (Geerr & Janssen, 2000), we can conclude that the data of the present studyy indicate that exposure to the sexual stimulus elicited a tendency for sexuall behavior in both men and women, and to the same degree in both genders. .
Experimentt 2
Introduction Introduction
Ass noted before, exposure to a sexual stimulus may, by modulating the internall state, enhance responses to subsequent sexual stimuli. Through activationn of reward circuitry in the brain, the attractiveness of sexual stimulii may increase. In this experiment, we studied the effect of a sexuallyy excited state on preference for and responsiveness to sexual stimuli. .
Emotionn research has revealed that the perceptual preference for specificc classes of stimuli is related to the current priority of concerns, andd that a person's emotional state influences the perceptual process. Forr example, research shows that clinical anxiety is associated with an attentionall bias for fear-arousing stimuli (e.g., Mogg, Mathews, &
Eysenck,, 1992). Furthermore, selective attention and anxiety are reciprocallyy related, although it is unclear if the perceptual changes are thee cause or the result of the emotional state (for review, see Williams, Mathews,, & MacLeod, 1996). To elucidate the effect of emotional state onn attention for particular stimuli, it is necessary to study attention followingg experimentally induced emotional states.
Inn the same way that an anxious state may affect the perception of fearr stimuli, a sexually excited state may influence the perception of sexuall stimuli. Stephan, Berscheid, and Walster (1971) found that sexuallyy aroused participants perceived attractive members of the oppositee sex as even more attractive. It seems likely that people in a sexuallyy excited state will try to continue and increase their sexual excitementt by searching for further sexual stimulation. Models of sexual excitementt assume that in sexually functional persons sexual excitement resultss in an attentional focus on erotic cues, which leads to increased sexuall arousal, which results in a further increase of attention for erotic cuess (Barlow, 1986). This positive feedbackloop is supposed to enhance sexuall responding and sexual approach behavior. However, in experimentss based on Barlow's model no direct measures were taken to assesss the hypothetical changed perception (van den Hout & Barlow, 2000).. In the present study, we performed a test of the prediction that a sexuallyy excited state is associated with increased interest for sexual stimulii by assessing preference for sexual stimuli following experimentally inducedd sexual arousal.
Perceptuall preference for particular stimuli may be reflected in the amountt of time a subject deliberately views those stimuli. Viewing time hass been used as a behavioral measure for interest in experimental studiess on emotional responses (e.g., Drobes, et al., 2001; Lang, Greenwald,, Bradley, & Hamm, 1993). Lang et al. (1993) found interest ratingss and viewing time to be associated with emotional arousal. Viewing timee of sexual stimuli has been used as an indicator of motivational approachh in different settings (e.g., Abel, Huffman, Warberg, & Holland, 1998;; Martin, 1964). Several studies showed that viewing time (called visuall reaction time) is longer for pictures congruent with the homo- or heterosexuall orientation of the participant (e.g., Abel et al., 1998; Wright && Adams, 1994, 1999) and is an accurate predictor of sexual interest in sexx offenders (Abel et al., 1998; Abel, Jordan, Hand, Holland, & Phipps,
2001;; Letourneau, 2002). Using visual reaction times, as opposed to directlyy asking participants about their preferences, offers the opportunity too measure interest more implicitly. In the present study, we did not use visuall reaction time as a measure for preference for a particular category off sexual stimuli, but as a behavioral measure for preference for sexual stimulii relative to neutral stimuli. We expected that sexual excitement wouldd increase preference for sexual stimuli, which would be reflected in longerr viewing times of sexual pictures.
Inn the present experiment we measured somatic motor preparation in responsee to the sexual stimuli in addition to genital responses. It has beenn established that the generation of sexual approach behavior will be accompaniedd by activity in the autonomic motor and the somatic motor system.. In an earlier study we used Achilles tendon (T) reflex modulation ass a measure for somatic motor preparation in response to sexual appetitivee stimuli (Both, Everaerd, & Laan, 2003). Subjective approach tendenciess and T reflexes were facilitated by exposure to sexual film. In thee present study, we used T reflex modulation to study the effect of activationn of the sexual reward system on subsequent responsiveness of thiss system. Since the pictures in the perceptual preference task were viewedd briefly, and somatomotor responses are much faster than autonomicc changes, measurement of T reflexes was most appropriate to studyy changes in activity in the motivational system. We expected the sexuall film and the sexual pictures to facilitate T reflexes more than the neutrall film and the neutral pictures. Also, we expected T reflexes in responsee to the sexual pictures to increase more strongly in the sexual filmm condition than in the neutral film condition.
Ass in Experiment 1, participants were exposed to a neutral or a sexuall film. Their physiological and subjective sexual responses to the filmm were measured, as were their subjective action tendencies and their sexuall desire and sexual activity during the 24 hours after the film exposure.. Different from Experiment 1, exposure to the neutral or sexual filmm was followed by a perceptual preference task. Half of the picture set usedd in this task had neutral content and the other half had sexual content.. Participants were asked to rate how sexually arousing they judgedd each picture. We measured the time the participant took to rate eachh picture and used it as an index for perceptual preference. We expectedd the sexual arousal induction to result in longer rating times for
thee sexual pictures, while we expected rating times for the neutral picturess to be unaffected by the sexual arousal induction.
Again,, both males and females participated to allow for comparisons byy gender. In addition, we evaluated the relationship between physiological,, subjective, and behavioral responses in men and women to providee insight into gender differences in the concordance of the various emotionall response systems. Generally, in women the relationship betweenn genital responses and subjective sexual arousal is weak or absentt (e.g., Laan & Everaerd, 1995a; Palace & Gorzalka, 1990), while in menn genital responses are generally highly correlated with subjective ratingss (e.g., Janssen et al., 1994; Koukounas & McCabe, 2001). Only a feww psychophysiological studies on sexual responses, however, included bothh sexes (e.g., Heiman, 1977; Steinman, Wincze, Sakheim, Barlow, & Mavissakalian,, 1981; Wincze, Venditti, Barlow, & Mavissakalian, 1980). Althoughh comparing male and female sexual responses is complicated forr several reasons (Geer & Janssen, 2000), studies in which both sexes participatee offer the best opportunity to investigate gender differences in sexuall response patterns. For correlational analyses we pooled the data off Experiments 1 and 2 and studied the relationship between genital response,, subjective sexual arousal, action tendencies, and sexual behaviorr in men and women. We expected a stronger relationship betweenn genital response and subjective response in men compared to women.. And, since in women genital response seems to determine the experiencee of a sexual situation only to a small extent (Laan & Everaerd, 1995a),, we expected to find in women a relatively weak relationship betweenn genital responding and postexperimental sexual behavior, but a strongerr relationship between subjective sexual arousal and postexperimentall sexual behavior. For men, the experience of a sexual situationn may be strongly determined by their genital response. Therefore,, we expected men's postexperimental sexual behavior to be relatedd to their genital as well as to their subjective sexual responses, andd to both these variables to the same degree.
Method Method
Participants Participants
Fifty-eightt participants (28 women and 30 men) participated. Most participantss (78%) were students. All participants received course credit orr were paid for their participation. Mean age of the women was 24.5 (rangee = 19-47 years, SD = 7.2 years) and mean age of the men was 27 (rangee = 19-46 years, SD = 7.1 years). There was no significant differencee in age between men and women, f{56) = 1.33, p > . 1 , or betweenn stimulus conditions, f(56) = 1.07, p > .1.
Twenty-threee female participants (82%) had a heterosexual orientation;; 5 women (18%) considered themselves bisexual. Eighteen womenn (64%) had a steady partner and duration of the relationships variedd from 1 month to 7 years. All had experienced sex with a partner, hadd experienced coitus, and had practiced masturbation. Four (14%) womenn reported that they experienced sexual coercion at least once in theirr life. Five women (18%) had not previously seen erotic films, and 4 womenn had no experience with erotic pictures.
Alll male participants had a heterosexual orientation. Fifteen men (50%)) had a steady partner, and duration of the relationships varied from 33 months to 22 years. All men except one had experienced sex with a partnerr and had experienced coitus. All men except one practiced masturbation.. None of the male participants reported sexual coercion experiences,, and all male participants had previously seen erotic films andd erotic pictures.
Thee procedures regarding information and informed consent were similarr to those in Experiment 1.
Design Design
Wee used a 2 (Film Content) x 2 (Gender) x 2 (Picture) design, with film contentt and gender as between-subjects variables and picture content as thee within-subjects variable. Again, men and women were randomly assignedd to the neutral or sexual film condition, with the restriction of equall numbers assigned to each condition. In both conditions the film wass followed by the perceptual preference task, which included 20 sexual andd 20 neutral pictures. The pictures were presented in random order.
MaterialsMaterials and response measurement
StimulusStimulus materials. Similar to Experiment 1, the two film excerpts
consistedd of 15-minute videotapes with sound. The neutral stimulus was aa documentary about Tibet. In the present experiment for the heterosexuall erotic videotape two scenes of more recent Candida Royallee films were used. Each scene depicted petting, cunnilingus, and intercourse.. A study in our laboratory, in which we compared responses too these female-centered film scenes to responses to male-centered film scenes,, showed that both men and women reported stronger feelings of sensualityy and positive affect in response to the female centered film sceness (Laan, 2004).
Thee picture set consisted of sexual and neutral pictures. Pictures with sexuall content portrayed heterosexual couples engaged in oral or genital sexuall activity. The neutral set depicted pictures of plants and bushes. WeWe selected pictures from pictures used previously in sexual response studiess in men and women (Janssen, Everaerd, Spiering, & Janssen, 2000;; Spiering, Everaerd, & Janssen, 2003).
PhysiologicalPhysiological recordings. Measurement of genital responses was
identicall to Experiment 1. We carried out the procedure for T reflex measurementt in accordance with standard methods for evoking T reflexess (Both et al., 2003). T reflexes were elicited by a hammertap at thee heel tendon. The hammertap at the tendon results in a reflexive electromyographicc (EMG) response in the soleus muscle of the lower leg. Whenn circumstances are held equal, taps of a constant force lead to reflexx amplitudes of constant size. Changes in reflex amplitude are a peripherall manifestation of supraspinal processes influencing spinal excitabilityy (Brunia & van Boxtel, 2000). To measure reflex activity (EMG), wee placed surface electrodes (Ag/AgCI electrodes, 2 cm2 contact area, 3 cmm apart) on participants' soleus muscle, along the longitudinal axis of thee calf, with the proximal electrode of the pair 2 cm distal to the insertion off the gastrocnemius muscle on the Achilles tendon. Reflexes were elicitedd at a constant rate of one every 7 seconds during the baseline and filmm presentation, which resulted in 25 reflexes during the 3 minute baselinee and 128 reflexes during the film presentation period. During the picturee viewing task, reflexes were elicited 1.5 seconds after picture onset.. To allow for a constant rate of reflex elicitation during the
picture-ratingg task, there was a constant timeframe of 5 seconds between the pictures.. Consequently, T reflexes were elicited once every 5 seconds.
Participantss were relaxed and passive throughout the tests, and they weree asked to refrain from moving during the recordings, except for pushingg the subjective rating button. The monitor was located in front of thee subject.
SubjectiveSubjective measurements and sexual behavior. Measurements of
subjectivee sexual arousal, emotional experience, subjective action tendencies,, and sexual behavior in response to the film excerpts were identicall to those used in Experiment 1. In the present experiment, to preventt drop-out we asked participants to return the day after the laboratoryy visit for administration of the questionnaire about sexual behavior.. At the end of the laboratory visit the experimenter made an appointmentt for at least 24 hours after participation. Again, the nature of thee questionnaire was not disclosed beforehand.
TheThe picture-rating task. A Macintosh PowerPC monitor was used for
picturee presentation and data collection. For the registration of responses,, we placed a button box in front of the participant. Images with aa size of 10 cm x 10 cm were presented on a black background. The sequencee of the 40 pictures was randomized afresh for each participant. Participantss were instructed to rate the arousability of the pictures by answeringg the question "To what degree do you find this picture sexually arousing?"" The question could be answered, using the button box, on a 7-pointt scale that varied from not at all to extremely. The picture presentationn was paced by the participants' responses. We measured ratingg time from onset of a picture to the pressing of a button. As noted before,, for the benefit of the reflex measurement we kept a constant picturee interval of 5 seconds. When a picture presentation was ended withinn this interval, a black background remained until the next picture wass presented.
Procedure Procedure
Thee procedure was identical to Experiment 1, except for the picture-rating taskk and the measurement of T reflexes during film and picture presentation.. A 3-minute return-to-baseline period followed film presentationn to allow for the determination of the T reflex amplitudes in responsee to the pictures relative to baseline amplitudes. To facilitate
returnn to baseline, we asked participants to count aloud backwards from 1000 during the first minute of this period. The return-to-baseline period wass followed by a 2-minute baseline period (Baseline 2), during which participantss listened to quiet music. Then the instructions for the picture taskk were shown on the monitor and the picture task started.
DataData reduction, scoring, and analysis
Reductionn and scoring of VPA and penile circumference data were similarr to Experiment 1. The same holds for the reduction and scoring of emotionall experience, subjective action tendencies, and postexperimentall sexual behavior.
Wee sampled EMG across baselines and subsequent stimulus presentationn periods. We calculated the mean T reflex amplitude elicited duringg Baseline 1 (X) and film presentation period (Y). We then calculatedd a percentage of baseline score (percentage of baseline = Y / X ** 100) for film presentation. For the T reflexes elicited during the picture-ratingg task, we calculated mean reflex amplitude during Baseline 2, mean TT reflex amplitude during sexual picture presentation, and mean reflex amplitudee during neutral picture presentation. Then we calculated a percentagee of baseline score in relation to Baseline 2 for sexual picture presentationn and for neutral picture presentation.
Inn addition, we calculated mean rating time for the picture viewing task,, and mean sexual arousability rating for the neutral and sexual pictures. .
Wee tested between-subject effects with multivariate and univariate analysiss of variance procedures. Within-subjects effects were tested with repeated-measuress univariate analysis of variance procedures (General Linearr model in SPSS). Statistical analyses of genital responses and subjectivee responses were similar to those in Experiment 1. We submittedd T reflex magnitude during film presentation to a 2 x 2 ANOVA withh stimulus and gender as between-subjects variables. Again, inspectionn of the postexperimental sexual activity data revealed extreme non-normalityy of the scores. Therefore, we used a statistical test for two Poissonn distributions.
Regardingg the picture-rating task, we submitted T reflex magnitude, ratingg times, and subjective ratings to 2 x 2 x 2 ANOVAs with stimulus
andd gender as between- subjects variables and picture as the within-subjectss variable.
Afterr pooling of the data of Experiments 1 and 2, we calculated Pearsonn product moment correlations between genital, subjective, and behaviorall responses for the sex film group only. Correlations were calculatedd for men and women separately. Given the large number of variabless that could be used in the correlational analysis, and given the degreee of error rate that would be introduced if all variables were included,, we decided to restrict the correlations to those central to the aimss of the study and to set the level of significance at a = .01.
Results Results
Responsess at exit interviews indicated that participants had felt comfortablee during the experiment despite the genital and T reflex measurements.. There were no differences between stimulus groups on thee pretest for the questions measuring sexual arousal and emotional experience.. Therefore, we used raw posttest scores for the multivariate analysis.. For both men and women, there was also no difference betweenn stimulus groups on the baseline measurement of genital response.. Likewise, we found no difference between groups or between menn and women on the baseline measurement of T reflexes.
Theree was no difference between men and women on the pretest for emotionall experience. However, subjective sexual arousal ratings during thee pretest were higher in women compared to men: for general feeling of sexuall arousal, F(3,54) = 19.61, p < .001; for strongest genital arousal, F(3,54)) = 23.13, p < .001. Therefore, for sexual arousal ratings we executedd the MANOVA with mean pretest score as covariate.
SubjectiveSubjective sexual arousal, emotional experience, and subjective action tendencies tendencies
Meann sexual arousal, emotional experience, and action tendency ratings aree shown in Table 3.
Tablee 3. Mean (SD) subjective ratings in response to neutral and sexual
filmm in Experiment 2.
Subjectivee ratings SexualSexual arousal Overalll sexual arousal3
Strongestt sexual arousal9
Strongestt genital sensations"
EmotionalEmotional experience0 Lust t Anger r Threat t Tension n ActionAction tendencies0 Approach h Avoidance/tension n Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Men n Women n Totall group Neutral l 1.3(1.1) ) 1.8(1.2) ) 1.6(1.1) ) 1.5(1.1) ) 2.3(1.4) ) 1.9(1.3) ) 1.4(1.1) ) 2.2(1.3) ) 1.8(1.2) ) 1.9(0.8) ) 1.99 (0.8) 1.9(0.8) ) 1.5(1.2) ) 1.4(0.5) ) 1.4(0.9) ) 2.11 (1.3) 1.9(0.6) ) 2.0(1.0) ) 2.0(1.8) ) 2.3(1.1) ) 2.11 (1.4) 1.9(1.0) ) 1.5(0.5) ) 1.7(0.8) ) 2.22 (0.5) 2.22 (0.4) 2.22 (0.4) Film m Sex x 4.4(1.4) ) 4.66 (0.9) 4.5(1.2)* * 5.44 (0.6) 4.11 (1.3) 4.8(1.2)* * 5.55 (0.6) 4.5(1.2)^ ^ 5.0(1.1)* * 3.7(1.4) ) 3.33 (1.1 \ 3.5(1.3)* * 1.3(0.5) ) 1.3(0.4) ) 1.3(0.4) ) 2.11 (0.4) 1.9(0.3) ) 2.0(0.4) ) 2.33 (0.9) 2.3(1.1) ) 2.3(1.0) ) 2.9(1.0) ) 2.6(1.0) ) 2.8(1.0)* * 2.33 (0.5) 2.55 (0.5) 2.4(0.5) ) Note.Note. Statistical significance of group comparison is reported for the total groups only.aa Item response format of 1 (not sexually aroused at all) to 7 (very strongly sexuallysexually aroused).b Item response format of 1 (no sensations in my genitals) to 77 (orgasm).c Item response format of 1 (not at all) to 7 (very strong). d Item responsee format of 1 (not at all) to 5 (very strong). Neutral versus sexual film groupp comparison statistically significant, p < .001.
SubjectiveSubjective sexual arousal. The main effect of stimulus was significant
forr sexual arousal ratings, multivariate F(3,52) = 36.36, p < .001. There wass no gender effect, but we did find a significant interaction effect of stimuluss and gender, multivariate F(3,52) = 6.45, p < .005. Univariate testss revealed that participants in the sexual stimulus group rated themselvess as more sexually aroused than participants in the neutral stimuluss group: overall sexual arousal, F(1,54) = 73.39, p < .001; strongestt feeling of sexual arousal, F(1r54) = 75.77, p < .001; strongest
genitall sensations, F(1,54) = 101.89, p < .001. We found an interaction effectt of stimulus and gender for strongest sexual arousal, F(1,54) = 14.34,, p < .001, and for strongest genital sensations, F(1,54)= 12.98, p = .001.. Ratings were highest in the male participants in the sexual stimulus condition.. A MANOVA with pretest ratings for sexual arousal as covariate revealedd the same pattern of results, with virtually no differences in p values. .
EmotionalEmotional experience. The main effect of stimulus was significant for
emotionall experience ratings, multivariate F(4,51) = 6.55, p < .001. There wass no effect of gender on emotional experience, and no interaction of stimuluss and gender. As expected, participants in the sexual stimulus groupp reported more feelings of lust than participants in the neutral stimuluss group, F(1,54) = 26.31, p < .001. There was no effect of stimulus onn feelings of anger, tension, or threat.
ActionAction tendencies. For action tendencies, the main effect of stimulus
wass significant, multivariate F(2,53) = 9.66, p < .001. There was no main effectt of gender and no interaction effect of gender and stimulus. Univariatee tests revealed that participants in the sexual stimulus group reportedd a stronger approach tendency compared to participants in the neutrall stimulus group, F(1,54) = 17.84, p < .001. The univariate test for avoidancee tendency was not significant.
GenitalGenital response and T reflex magnitude in response to the film
GenitalGenital response. Due to technical problems, genital data from one
malee participant were missing. We found a stimulus effect on penile circumferencee change, F(1,27) = 19.00, p < .001. The men in the sexual stimuluss group showed a larger increase in genital response compared to thee men in the neutral film group. Similarly, in women genital response
wass larger in the sexual film group than in the neutral film group, F(1,26) == 25.63, p < .001 (see Table 4).
TT reflexes. As expected, we found an effect of stimulus on T reflex
magnitude,, F(1,54) = 12.71, p < .005. T reflex magnitude was higher in thee sexual stimulus group than in the neutral stimulus group. Contrary to expectations,, there was no effect of gender and no interaction of gender andd stimulus.
Tablee 4. Mean genital response (SD) to neutral and sexual film in
Experimentt 2.
Penilee circumference* Vaginall pulse amplitude
Neutral l 100.53(4.07) ) 81.811 (24.45) Film m Sex x 114.89(9.36) ) 196.82(68.92) )
Note.Note. Units are percentage of baseline (response during film / baseline * 100).
** Neutral versus sexual film group comparison statistically significant (p < .001, menn df = 1,27, women df = 1,26).
ResponsesResponses during the picture-rating task
Meann rating times, arousability ratings, and T reflex magnitudes in responsee to the pictures are shown in Figure 2.
PicturePicture rating times. Due to technical problems rating times from five
participantss in the neutral film condition were missing. Inspection of the dataa revealed that participants had relatively long rating times for the first picture.. We found a difference between mean rating time for the first picturee and the subsequent pictures, F(1,8) = 9.32, p < .05. Therefore, we decidedd to remove the rating time for the first picture.
Wee performed a 2 x 2 x 2 repeated measures ANOVA with stimulus conditionn and gender as between-subjects factors and picture (sexual versuss neutral) as the within subjects factor. There was a main effect of picturee content, F(1,49) = 124,52, p < .001. Participants had longer rating timess for the sexual pictures compared to the neutral pictures. There was alsoo an effect of stimulus condition, F(1,49) = 6.07, p < .05, such that participantss in the sexual stimulus condition had shorter rating times than participantss in the neutral stimulus condition. The effect of gender
approachedd significance, F(1,49)= 3.47, p = .07; women had longer rating timess compared to men. We found an interaction effect of stimulus conditionn and gender, F(1,49) = 4.99, p < .05; women in the neutral stimuluss condition had relatively long rating times. We found no other effects. .
ArousabilityArousability ratings. We found only a main effect of picture, F(1,49) =
84.39,, p < .001. Participants rated the sexual pictures as more sexually arousingg compared to the neutral pictures.
TT reflexes. Due to technical problems, T reflex data were missing for
onee participant in the sexual stimulus condition and for five participants in thee neutral stimulus condition. To investigate possible differences in T reflexx baselines, which may impact stimuli effects, we performed a 2 x 2 x 22 repeated measures ANOVA with stimulus and gender as between-subjects,, and time as within-subjects variable. This analysis revealed an interactionn effect of time and stimulus, F(1,48) = 5.37, p < .05. In the sexuall stimulus condition, reflexes during Baseline 2 were higher than duringg Baseline 1, indicating that participants' T reflex activity did not returnn to baseline levels during the return-to-baseline period preceding thee picture-rating task. Therefore, we also ran the statistical analysis with meann T reflex during Baseline 2 as covariate.
Reflexx magnitude was higher during sexual picture viewing compared too neutral picture viewing, F(1,48) = 19.98, p < .001. There was also a mainn effect of stimulus condition, F(1,48)= 4.12, p < .05: T reflex magnitudee during picture viewing was higher in the neutral stimulus condition.. There was no main effect of gender and no interaction between stimuluss condition and gender. Also, interactions between picture and stimuluss condition and between picture and gender were absent. The interactionn between picture, stimulus condition, and gender approached significance,, F(1,48) = 3.84, p = .06. Men who had seen the neutral film priorr to the picture-rating task had a relatively high T reflex magnitude in responsee to the sexual pictures.
Thee repeated measures analysis with mean T reflex amplitude during Baselinee 2 as covariate revealed largely the same pattern of results. Reflexx magnitude was higher during sexual picture viewing compared to neutrall picture viewing, F(1,47) = 17.01, p < .001, and the interaction betweenn picture, stimulus condition, and gender was significant, F(1,47) == 4.84, p < .05.
o o < < z z 1.5 5 1 1 Arousabilityy ratings (b) Hmenn N Bwomenn N Dmenn S T T
I I
i i T T T T 3000 0neutrall film sexual film Stimuluss Condition
Ratingg times (a)
neutrall film sexual film Stimuluss Condition TT reflex magnitude (c) CD D ii 180 .trr co §>££ 160 coo o EE o ** j?140 CDD CU *-- t l I ll men N Dmenn S = = =
T T T T
neutrall film sexuall film Stimuluss Condition
Figuree 2. Mean arousability rating (a), rating time (b), and T reflex
magnitudee (c) with SEM in response to the neutral (N) and sexual (S) pictures,, in the neutral versus sexual stimulus conditions.
CorrelationsCorrelations between rating times and arousability ratings of the sexual pictures pictures
Wee expected rating times to reflect sexual interest. Therefore, we expectedd that the rating times of the sexual pictures and the arousability ratingss would be related. The correlation between rating time and arousabilityy rating of the sexual pictures was .23 (p < .1). Although this correlationn is moderate to low, it does indicate that the time participants deliberatelyy looked at the sexual pictures was related to how sexually arousingg participants thought the pictures were. Moreover, when correlationss for both stimulus groups were calculated separately, the correlationn between rating time and arousability rating of the sexual picturess in the sexual film group was .41 (p < .05), and in the neutral film groupp .07 (ns). Thus, only in the sexual arousal condition was the time participantss looked at the sexual pictures related to how sexually arousingg they thought the pictures were.
SexualSexual behavior
Onee male participant did not show up to complete the postexperimental sexuall behavior questionnaire. Consequently, we ran the analysis with 30 participantss (15 men and 15 women) in the sex film group and 27 participantss (14 men and 13 women) in the neutral film group.
Postexperimentall sexual desire and activity ratings are shown in Figuree 3. Regarding the postexperimental sexual desire score, the univariatee analysis revealed no effect of stimulus, F(1, 53) = .86, p = .36, andd a significant effect of gender, F(1, 53) = 4.92, p < .05. The male participantss had higher postexperimental sexual desire scores compared too the female participants. The male participants in the sexual stimulus groupp scored highest on sexual desire; however, the interaction of stimuluss and gender did not reach significance, F(1, 53) = 2.22, p = .14.
Forr postexperimental sexual activity scores there was an effect of stimulus,, z = 1.97, p < .05. Participants in the sexual stimulus condition reportedd more sexual activity after the experiment (M = 1.25) than did participantss in the neutral stimulus condition (M = 0.75). There was no significantt difference between men and women in postexperimental sexuall activity.
Postexperimentall sexual desire (a) 'w w O O -a -a aa 1 15 5 22 1 0.5 5 00 L
T T
T TI I
T T
men n DD women T T I Ineutrall film sexual film Stimuluss Condition
Postexperimentall sexual activity (b)
DD men -- Dwomen
neutrall film sexual film Stimuluss Condition
Figuree 3. Mean postexperimental sexual desire (a), and sexual activity
(b)) ratings with SEM in the neutral and sexual stimulus condition in Experimentt 2.
Inn the sexual stimulus condition, 60% of the participants had a steady partner.. In the neutral stimulus condition this percentage was 56%. Of the men,, 54% had a steady partner; of the women, 6 1 % had a steady partner.. The chi-square tests revealed no significant difference between conditionss or between men and women.
Regardingg the wish to have been less or more sexually active during thee 24 hours following participation, we found no significant difference betweenn conditions. In the sexual film condition, 57% of the participants reportedd that their amount of sexual activity was just right, 30% reported
thatt they had wished to be somewhat more active sexually, and 13% reportedd that they had wished to be much more active sexually. For the neutrall film condition, 7% reported that they had wanted to be much less sexuallyy active, 4% reported that they had wished to be somewhat less activee sexually, for 4 1 % it was just right, 26% reported they had wanted too be somewhat more sexually active, and 22% had wanted to be much moree active sexually.
Forr men and women there was a marginally significant difference in thee distribution of the reported wish to be less or more sexually active, % (4)) = 8.98, p = .06. For the men, 7% reported that they had wished to be muchh less sexually active, 3% reported they had wished to be somewhat lesss active sexually, for 45% it was just right, 17% reported they had wishedd to be somewhat more sexually active, and 28% wanted to be muchh more active sexually. Among the women, 54% of the participants reportedd that their amount of sexual activity was just right, 39% reported thatt they had wished to be somewhat more active sexually, and 7% reportedd that they had wished to be much more active sexually.
CorrelationsCorrelations between genital response, subjective responses, and postexperimentalpostexperimental sexual desire and activity
Correlationss between genital, subjective, and behavioral responses were calculatedd for the sexual stimulus group only, and for men and women separatelyy (see Table 5).
Inn line with our expectations, the correlations between genital response,, subjective sexual arousal ratings, and feelings of lust were low (rangingg from -.01 to .15) in women, while these correlations were higher inn men (ranging from .30 to .42). Although the correlations between genitall and subjective responses in men were moderate, they did not reachh significance.
Inn men and women there were, as expected, substantial correlations betweenn subjective sexual arousal and approach ratings. However, only thee correlation between strongest genital sensations and approach was significant.. In women there was, as expected, a low correlation between genitall response and postexperimental sexual activity, and higher correlationss between lust, approach, and sexual arousal ratings and postexperimentall sexual activity. Postexperimental sexual desire was alsoo related to feelings of lust and approach ratings. Contrary to our
