The relation between sexual interest and personality characteristics in men: an eye-tracking study

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Abstract

There is a large individual deviation for men, which may be caused by a difference in personality characteristics, in sexual interest in response to sexual stimuli. In this study, we investigate whether attention to the sexual region in a video depends on the personality characteristics of men, assessing this with an eye-tracking system. The study included 30 healthy males with a normal psychological state, who viewed a sexual video in which the sexual region had been designated. Visual attention was measured across the designated region according to gaze duration. Ten types of personality characteristics were evaluated as a T-score by a questionnaire. By Pearson’s correlation coefficient, the relations between gaze duration at the sexual region and T-scores of paranoia, psychasthenia and social introversion were found to be statistically significant. By multivariate stepwise regression analysis, only social introversion was negatively associated with the sexual region. Even normal variation of personality characteristics can affect the viewing period of the sexual region. This is the first report showing that subjects with a high degree of paranoia, psychasthenia and particularly social introversion have a tendency to view the sexual region for a shorter duration.

Introduction

Sexual function has an important role with respect to quality of life. A selective inhibitor of PDE5 that inhibits the degradation of cyclic guanosine monophosphate in the corpus cavernosum of the penis has been widely used and is effective for patients with ED.1 However, although PDE5 inhibitor can improve erectile function, it cannot evoke sexual interest. Although it has been believed that testosterone replacement can increase sexual interest and sexual libido in patients with hypogonadism, there is no effective medication available for the treatment of loss of sexual interest. The topic of sexual interest has attracted increased attention from researchers as a new area of investigation alongside ED. When erection is not induced by audiovisual sexual stimulation (AVSS), a reliable diagnosis may not always be possible, as patients might not concentrate while viewing the AVSS because of lack of sexual interest or personal preferences for sexual stimuli.

Despite the increased attention in sexual interest, there has been no reliable and assessable quantitative method to evaluate it, although several questionnaires and patient self-reports of sexual desire have been used as tools for assessing it. The authors have recently constructed a new eye-tracking system in which eye positions of subjects were recorded automatically while viewing sexual videos to evaluate those regions of the video that were of interest to subjects.2 By this method, we recently reported that a sex difference existed in visual attention to a sexual video; men viewed the opposite sex for longer periods than did women, and women viewed the same sex for longer periods than did men. Interestingly, we also found in that study that there was a large individual deviation for men in sexual interest in response to sexual stimuli in the sexual video. It was speculated that this large individual deviation may be caused by personal preference based on a difference in personality characteristics. Thus, in this study, we investigate whether attention to the sexual region depends on personality characteristics of male volunteers by using the authors’ eye-tracking system.

Materials and methods

Participants

Thirty healthy and heterosexual men (mean age, 35.2±4.2 years) participated in this study. Written informed consent according to the Declaration of Helsinki was obtained from all volunteers. All participants were recruited from our personal acquaintances by personal communication and each subject was informed that the study was regarding visual responses to videos. All participants underwent a screening interview regarding sexual activity by one physician (AT) and participants whose sexual arousal was found to be diminished were excluded from the study. Psychopathological abnormality was assessed with the Minnesota Multiple Personality Inventory-2 (MMPI-2) by a clinical psychotherapist (MM). All participants were Japanese, highly educated, married and they were not compensated for their participation. The procedures were approved by the Regional Ethics Committee of the Osaka University Graduate School of Medicine.

Sexual stimuli

The authors’ methodology has previously been published.2 In brief, the subjects viewed audiovisual material in the form of a sexually explicit video clip, which was used for sex research for the first time and by which several statistically significant sex differences were found in viewing patterns in our previous study. The content of this clip was of a naked actor and actress kissing and touching each other. For this clip, the region of the actress’s naked body was defined as the most attractive sexual region in each frame by QG Eye-Tracking Software (Nihon Binary, Tokyo, Japan). The designation of this region was not visible to the participants. The length of evaluation of this designated region was 40 s.

Procedure

The authors’ procedure has previously been published.2 In brief, eye movements of subjects were measured with a Quick Glance 2 Eye Tracker System (EyeTech Digital Systems, Mesa, AZ, USA; Figure 1). The system consists of EyeTech TM2 software installed on a laptop computer, two infrared lights mounted on each side of the monitor and a camera placed on the keyboard. To prepare for testing, each subject was positioned in front of the laptop computer, and his position was calibrated to the position of the laptop screen on the basis of 16 calibration points. If the calibration data proved inadequate, repeated calibration was automatically required. After successful calibration, the participants were requested to view the prepared clip on the laptop screen with no additional tasks required. Participants viewed privately and their eye positions were recorded. These data indicated what the subject was viewing relative to gaze-point coordinates on the screen surface. Data points were obtained 40 times per second. This methodology allowed for the measurement of gaze duration on the designated sexual region.

Figure 1
figure1

Quick Glance 2 Eye Tracker System (EyeTech Digital Systems) with laptop computer. The monitor shows a calibration scene.

Evaluation of personality characteristics

Ten personality characteristics including hypochondria, depression, hysteria, psychopathological deviation, self-esteem, paranoia, psychasthenia, schizophrenia, hypomania and social introversion were evaluated according to the MMPI-2 with 550 alternative questions. MMPI-2 is one of the most frequently used personality tests worldwide.3 We required the respondents to answer either ‘True’ or ‘False’ to each item. The raw score on each dimensional scale was converted to a T-score with a mean of 50 and a standard deviation of 10 after K-correction.4 The value of the T-score was estimated to be equal to the normal distribution in multidimensional scaling.

Data analysis

Total gaze time for the region of the actress’s naked body was taken as an indication of sexual interest, and the gaze time for this region relative to total viewing time was calculated. All data are presented as mean±s.d. To investigate the relation between sexual interest and personality characteristics, Pearson’s correlation coefficient between the gaze duration for the region of the actress’s naked body and the T-scores of the 10 personality characteristics was performed. Furthermore, multivariate stepwise regression analysis among the T-scores of the 10 personality characteristics was also performed. A P-value <0.05 was considered to be statistically significant for Pearson’s correlation coefficient. A P-value <0.01 was considered to be statistically significant for multivariate stepwise regression analysis, because some significant findings can be found by chance in multiple comparison.

Results

The mean gaze duration for the actress's naked body was 13.4±8.9%. The mean T-score of each personality characteristic by MMPI-2 is shown in Table 1. An abnormal T-score was not found in any participant in any personality subtype.

Table 1 Personality characteristics evaluated by the Minnesota Multiple Personality Inventory-2

Regarding the gaze duration for the sexual region, three personality characteristics were associated negatively (paranoia, Pearson’s r correlation −0.381, P<0.05; psychasthenia Pearson’s r correlation −0.402, P<0.05; social introversion, Pearson’s r correlation −0.492, P<0.01; Figure 2). Regarding the gaze duration for the sexual region, multiple stepwise regression analysis showed that only social introversion was associated negatively (regression coefficient, −0.337, P<0.01).

Figure 2
figure2

Statistical significance was found in the relations between the gaze duration of the actress’s naked body (sexual region) and T-scores for paranoia, psychasthenia and social introversion by Pearson’s correlation coefficient.

Discussion

Until now, it has been unclear how and what personality characteristics could affect sexual activity, including interest. It was recently reported that specific personality subtypes, introversion and emotional instability seem to be significant risk factors for orgasmic infrequency in women.5 However, few studies have been conducted to investigate the relation between sexual interest and personality characteristics in men. Furthermore, there has been no study to investigate this relation in men with an eye-tracking system as a reliable methodology for assessing visual attention to sexual stimuli, with which we and other researchers have reported a sex difference in sexual interest.2, 6, 7

We found clearly by using Pearson’s correlation coefficient in this study that, as the degree of paranoia, psychasthenia and social introversion in the personality grew stronger, sexual interest in the sexual region became weaker. Paranoia is a psychology characterized by excessive anxiety or fear. It often induces irrationality and delusion, which concern experiences that can conceivably occur in real life, such as being followed (persecutory type), having a disease (somatic type), being loved at a distance (erotomanic type), possessing inflated worth, power, identity or knowledge (grandiose type), and having an unfaithful sexual partner (jealous type).8 Regarding persecutory delusion, it was reported to be a predictor of homosexual concern in a study of over 4000 patients.9 It was also reported that 24% of hospitalized male homosexuals had paranoid ideation.10 Although our participants were not diagnosed with abnormal paranoia, it is speculated that people with a high degree of paranoia are unlikely to be indifferent about heterosexual stimuli. People with psychasthenia, which is a psychological disorder characterized by phobias, obsessions, compulsions or excessive anxiety, have insufficient control over their conscious thinking and memory. The constant mental effort and characteristic insomnia induce fatigue, which exacerbates the condition. Thus, it is also reasonable that subjects with a high degree of psychasthenia, and the corresponding mental and physical fatigue, would not concentrate while viewing the sexual region. Other than these two personality characteristics, social introversion was the key characteristic for negative correlation with the sexual region, because multiple stepwise regression analysis showed that only social introversion was statistically significant. This finding is consistent with a previous study using questionnaires showing that social introversion resulted in a significant negative correlation with autoerotic stimulation and arousal.11 Introversion is the state of or the tendency toward being wholly or predominantly concerned with and interested in one's own mental life. As the interest and imagination of inverts are stimulating enough, these personalities are reluctant to derive stimulation from others. Thus, people with a high degree of this personality characteristic may not be interested even in sexual stimuli.

The purpose of the AVSS test is to distinguish psychogenic ED from organic ED. If patients do not view AVSS because of diminished or loss of sexual interest, the test itself becomes meaningless. Thus, the AVSS test has the potential of a large number of false negatives; for example, if erection is not induced by AVSS because of the lack of concentration during viewing. Furthermore, although recent activation studies12, 13 including the authors’ own14, 15 using neuroimaging of the central nervous system during sexual arousal and erection have shown several important and activated regions, they can be relied on only when a subject concentrates on viewing the AVSS. It would be necessary to confirm for certain whether visual attention is focused on sexual stimuli in the AVSS during the test and during these activation studies. Our findings clearly showed that sexual interest in the sexual region defined by the actress’s naked body correlated with some personality characteristics. Therefore, personality characteristics of subjects should be considered in the evaluation for sexual activity, particularly when using AVSS and activation studies.

Conclusions

This study showed that even a normal variation of personality characteristics can have an effect on the viewing period for the sexual region in a test video. This is the first report showing that subjects with a high degree of paranoia, psychasthenia and social introversion have a tendency to view the sexual region for a shorter duration than subjects without these personality traits. We speculate that such patients should be carefully diagnosed when the AVSS is being used, because they have personality characteristics suspected of causing false negatives.

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Correspondence to A Tsujimura.

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The authors declare no conflict of interest.

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Tsujimura, A., Miyagawa, Y., Takada, S. et al. The relation between sexual interest and personality characteristics in men: an eye-tracking study. Int J Impot Res 22, 185–189 (2010) doi:10.1038/ijir.2009.61

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Keywords

  • sexual interest
  • sexual video
  • men
  • eye tracking
  • personality characteristics

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