Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Women's Preferences for Penis Size: A New Research Method Using Selection among 3D Models

  • Nicole Prause ,

    Contributed equally to this work with: Nicole Prause, Geoffrey Miller

    nicole.prause@gmail.com

    Affiliation: Department of Psychiatry, University of California Los Angeles, Los Angeles, California, United States of America

  • Jaymie Park ,

    Affiliation: Department of Psychiatry, University of California Los Angeles, Los Angeles, California, United States of America

    ‡ These authors also contributed equally to this work.

  • Shannon Leung ,

    Affiliation: Department of Psychiatry, University of California Los Angeles, Los Angeles, California, United States of America

    ‡ These authors also contributed equally to this work.

  • Geoffrey Miller

    Contributed equally to this work with: Nicole Prause, Geoffrey Miller

    Affiliation: Department of Psychology, University of New Mexico; Albuquerque, New Mexico, United States of America

Women's Preferences for Penis Size: A New Research Method Using Selection among 3D Models

  • Nicole Prause, 
  • Jaymie Park, 
  • Shannon Leung, 
  • Geoffrey Miller
PLOS
x

Abstract

Women’s preferences for penis size may affect men’s comfort with their own bodies and may have implications for sexual health. Studies of women’s penis size preferences typically have relied on their abstract ratings or selecting amongst 2D, flaccid images. This study used haptic stimuli to allow assessment of women’s size recall accuracy for the first time, as well as examine their preferences for erect penis sizes in different relationship contexts. Women (N = 75) selected amongst 33, 3D models. Women recalled model size accurately using this method, although they made more errors with respect to penis length than circumference. Women preferred a penis of slightly larger circumference and length for one-time (length = 6.4 inches/16.3 cm, circumference = 5.0 inches/12.7 cm) versus long-term (length = 6.3 inches/16.0 cm, circumference = 4.8 inches/12.2 cm) sexual partners. These first estimates of erect penis size preferences using 3D models suggest women accurately recall size and prefer penises only slightly larger than average.

Introduction

Both men and women often have reported discomfort with the appearance of their genitals. While not as common of a concern as body weight, muscularity, amount of head hair and body hair, or height, penis size was a concern for 68.3% of 200 men in one study [1]. Concerns about genital appearance are unique compared to other concerns about physical appearance. First, only intimate partners generally know the appearance of genitals. In contrast to the penis, body weight, acne, and other features are easily observed, informing feelings of attraction early in interactions. While indicators of penis size include ethnicity [2] and finger length and ratio [3, 4], most proposed cues of penis size, including male height and foot size [5], weight [6, 7], shoe size [8], and age [9], are unreliable. Second, no diet, pill, or exercise regime affects the size or shape of genitals. However, about half of men in one study believed that they could change their penis size through non-surgical means [10]. Little can be done to change the appearance of the penis. Contrary to some public opinion, it also is worth noting that discomfort with the appearance of the penis is not impacted [11], or is positively impacted [12], by viewing sex films. Given that only intimate partner(s) view the penis, the appearance is relatively immutable, and sex films are not causing dissatisfaction, partner perceptions of the penis appearance seem to most likely to impact men’s feelings about the features of their penis.

The expectations that men have about women’s penis size preferences appear to drive anxiety and dissatisfaction more than some inborn dissatisfaction. In the first questionnaire to examine the nature of dissatisfaction with the penis directly, three of the ten items concerned a partner’s perception [13]. These included “I will be alone and without a partner” and “I will be laughed at by a partner in a sexual situation”. These anxieties may be unnecessary. For example, while men and women agreed that the “ideal” penis length was longer than what they thought was average, men mistakenly reported that women would find an even longer penis ideal than the women actually did [10]. Furthermore, most men seeking surgery to increase their penis size (e.g., [14, 15]), actually fall within the normal penis size range [16].

Concerns about penis size affect men’s sexual satisfaction and functioning. Of course, penis size need not affect sexual functions like orgasm, sexual drive, or pain experience. However, men who are less satisfied with their penis report more sexual health problems [17]. A smaller penis decreases sexual confidence [18], which may be why penis size is related to sexual function. Another reason penis size may be related to sexual functioning is that anxiety concerning the partner’s response may be calculated as a cost of the relationship, which leads him to experience broad sexual dissatisfaction [19].

The context of the sexual relationship could influence penis size preferences. For example, the goal of the sexual interaction with a one-night partner tends to be pleasure [20]. Women recognize that infection risks are higher from a one-night partner [21]. While women adjust their behaviors for this risk, being less likely to engage in anal sex [22] and more likely to use condoms [23] with one-night partners, such risky behaviors themselves are often experienced as pleasurable [24]. On the other hand, vaginal intercourse always causes tears in the vaginal mucosa [25] especially in the sensitive posterior fourchette [26], so women might prefer a smaller penis less likely to stress their physiology for regular, long-term mates. Thus, women might shift their preferences for penis size depending on the type and duration of sexual relationship.

Studies of penis size preference to date have relied on numerical size estimates, vague qualitative descriptions, or 2-D line drawings. For example, some studies have asked participants to specify penis length preferences in centimeters [27]. Another study asked participants to indicate their preference from reading erotic passages with three qualitative penis size options (small, medium, large) [28]. Yet, humans judge sizes most accurately when visual and haptic information are available together [29]. Both sources of data are usually available in sexual interactions. Thus, in this study, three-dimensional (3D) models were used with the hope of increasing accuracy, ecological validity, and external validity. Also, most studies of penis size preference have portrayed or asked about the penis in its flaccid state [30, 31]. This may be problematic, because the relationship between erect and flaccid sizes has been reported as negligible [32, 33] moderate (r = .44 in [34], r = .78 in [35]), and strong (rho = .77 in [6], r = .79 in [32]). It is unclear how well flaccid size reflects erect size. Of course, intercourse can occur only with a sufficiently rigid penis [36]. Thus, it seemed important to characterize preferences for penis size in its erect state. The current study used 3D models of erect phalluses to characterize women’s penis size preferences for the first time.

Three-dimensional (3D) printing is just beginning to be used to assess shape perception and categorization. On the one hand, visual 2D information as compared to haptic information (from 3D) result in similar solutions for object similarity [37]. Each mode of information (visual or haptic) also improves categorization in the other domain [38, 39]. 3D printing could allow representation of highly problem-specific, complex structures [39]. Haptic information from 3D objects improved shape identification compared to raised lines alone [40] and improves later performance in the visual domain [41], possibly by improving discriminability [42]. Also, haptic information is robust to differences in perceptual acuity, such as occur with aging [43], which make such stimuli attractive when the visual acuity of participants may vary. This study extends the existing work using 3D stimuli to assess size preferences. This approach also permitted characterization of women’s ability to accurately recall the size of erect phallus models for the first time.

When flaccid and “stretched” penis sizes are characterized [44], largely by self-measurement [45], they predict erect size surprisingly poorly. Yet there are relatively few studies of erect penis size. This may reflect cultural taboos against researchers or doctors interacting with men who are in a sexually aroused state. One study had men judge their own erect size in relation to a banknote’s length [46]. Two studies of erect penis sizes provided kits for home measurement [47, 48]. Such self-measurements of length and circumference show fairly good test-retest reliability (r = .68 to .90, [47]). Pharmacologically-induced, physician-measured erections identified an average length of 12.89 cm (SD = 2.91) and circumference of 12.3 cm (SD = 2.9; [32]). These were somewhat shorter in length (M = 14.15, SD = 2.7), yet similar in circumference (M = 12.23, SD = 2.2), compared to a recent, large survey [48].

Women’s penis preferences may vary with their relationship expectations. Women prefer more masculine partners for shorter-term sexual relationships [20]. Women also value intelligence more, and attractiveness less, for long term, as compared to short term, partners [49]. More masculine traits, such as lower voice pitch [50] and (to some extent) larger penis size [51, 52] are correlated with testosterone levels, which also may influence men’s mating goals and attractiveness. Since a larger penis size is perceived as more masculine [53, 54], we predict women will prefer a larger penis for shorter-term sexual relationships.

Women likely make penis size judgments partly using their recalled experiences. Yet, it is unclear how accurately women can recall penis size. Exposed to nude male images, women do attend to the genital area [55, 56]. People can generally recall if a penis was described as “large”, “medium”, or “small”, or not described at all [28]. In the current study, women’s ability to recall penis size was tested by match-to-sample recall, both immediately and after a delay of ten minutes.

Materials and Methods

Stimuli: The penis models

Based on previous studies (see above) about the distributions of penis length and circumference, the average American erect penis length was estimated as 6 inches (15.2 cm) and circumference as 5 inches (12.7 cm). Models were created to range +/- 3.0 S.D. across each dimension (see Fig 1). This resulted in length ranging 4.0 inches to 8.5 inches (10.2 cm to 21.6 cm), and circumference (circumference) ranging from 2.5 inches to 7.0 inches (6.4 cm to 17.7 cm), using 0.5-inch (1.3 cm) increments (see Fig 1). This yielded a 10 X 10 matrix of 100 possible sizes. However, such a large choice set could overwhelm participants. We chose to sample 1/3 of this space, yielding 33 models across the range of space.

thumbnail
Fig 1. Sizes of printed models.

Shading indicates the average penis length and girth in the USA. Bold indicates models used for recall (immediate/delayed, counterbalanced) tests. Units are in inches.

http://dx.doi.org/10.1371/journal.pone.0133079.g001

The penis model shape was a cylinder, representing the shaft, topped by a dome, representing the penis head (see Fig 2). Of course, the human penis shaft is comprised of three corpora that could be better represented by a rounded triangle and a more complex glans. Also, no veins, testicles, or other details of the penis were portrayed. These details were not represented for three reasons. First, there are no mathematical descriptions available to accurately represent normal proportions of more complex penile structure. Second, women generally rate male nudes as less attractive than heterosexual men rate female nudes [57], so making the penis model more realistic might have provoked negative responses. Third, the study was focused on overall penis size, not penis shape or surface details. While one motivation behind the current study was to improve the ecological validity of the stimuli, these concerns suggested starting with a more simplistic, erect penis model.

thumbnail
Fig 2. Penile Models.

A) Computer graphic representation of one of the ‘print files’ used to produce the 3D penis models. B) Examples of (4 of 33) 3D models showing length in inches. A and D represent the largest and smallest models in the set, respectively; B and C represent the two models (counterbalanced) used to test recall for size.

http://dx.doi.org/10.1371/journal.pone.0133079.g002

Dimensions of commercial penile models do not vary systematically, so they were not appropriate for research purposes. Thus, the penis models were printed using a Makerbot Replicator 2 in blue ABS plastic (“Navy wool”; printer files for replications are at http://www.thingiverse.com/thing:518401). Files were created using object-oriented Tinkercad [58] and compiled to.stl formats in G-Replicator [59]. Models were light-weight, sturdy plastic with a smooth surface (see Fig 1). After printing, models were checked by measuring tape to ensure accuracy of length and circumference. None required reprinting for accuracy. The models were identified by randomly assigned letters (e.g., “M”, “CC”) written on the bottom of each. This was done to reduce the influence of “largest” and “smallest” anchors and also to eliminate the need for women to measure or infer specific size. The 33 models were evenly split (11, 11, 11) in a three-tier wire basket to ease women’s ability to find the desired model. Baskets were randomly shuffled between participants to reduce selection bias.

Participants

Volunteer were recruited by flyers around the California university campus, the neighborhood, and local physicians’ offices. The flyers stated that women were requested to volunteer for a study concerning sexuality. The flyers also stated that participants must be female, at least 18 years old, sexually attracted to men, and would be paid $20. The flyer did not mention penis size preferences. Women volunteered by either phone or an online form requesting a phone call. They completed a phone screening to confirm their eligibility (e.g. being aged 18 or over, being sexually attracted to men) before being scheduled as participants.

Procedures

Upon a participant’s arrival, the Informed Consent document was provided, and women were given time to study it. Afterwards, they were given a chance to ask questions, then the experimenter asked whether they still wish to participate. If the participant verbally consented, the experimental protocol started. The Informed Consent document stated that continuing at this stage constituted consent. Participants never provided their names. Informed Consent was not documented using identifiable personal information, because it was unclear whether the new procedures might influence participants’ willingness to report their penis size preferences.

Next, the participant answered questionnaires (described below) presented on a computer in a private room, using a secure connection, on private laboratory server space scripted by the first author in php5. This took about 50 minutes and included the penis size preference tasks and questionnaires (see below). Computer presentation of questionnaires has been shown to increase the reporting of socially less desirable behaviors [60]. After the questionnaires, she completed a 10-minute computer task (data to be reported elsewhere) assessing attention to sexual images. Afterwards, the participants was debriefed, offered the opportunity to ask questions, and given $20 cash. The study protocol, including Informed Consent protocol, was approved by the University of California, Institutional Review Board.

Questionnaire

The self-report questionnaires included demographic information (e.g., age, ethnicity, sexual orientation), sexual history (e.g., number of sexual partners, sexual coercion, whether penis size played a role in relationship dissolution(s), etc.), and current sexual functioning (e.g. orgasm rates, ease of lubrication, relationship monogamy status, pain during intercourse). These were used to characterize the sample. Other personality questionnaires were included, such as the Sexual Desire Inventory [61] and the Sociosexual Orientation Scale [62] to characterize the sample.

Size preference and recall: Recall accuracy

After completing the other questionnaires, the experimenter entered with one of the two test models. Two of the original 33 models were randomly selected and reprinted (indicated in black cells in Fig 2). The experimenter informed the participant that she would be handed a model. She was instructed that she would be asked to try to recall the size of the model after inspecting it. During the inspection, she was asked not to measure the model using any objects in the room, but no instruction was provided regarding how she used her own hands. Then, the experimenter left for 30 seconds (without observing the participant’s inspection process), returned, took the test model from the participant and out of the testing room, and asked the participant to select which penis model (from the 33 described above) was most similar in size to the test model she just handled. The participant recorded the letter code from the bottom of that model into the computer.

The delayed-recall task was similar, except this time, the participant did not immediately search for the model. Instead, she was given ten minutes to complete the penis size preference questionnaire (below). The preference questionnaire would increase memory interference, which is desirable for ecological validity as women asked to recall a former partner’s penis size may have sex with other new partners in the delay. After this, the participant was instructed to attempt to locate the second model (from the 33 described above). The test models were counter-balanced, so the recall type (immediate or delayed) would not be confounded with test model size (larger or smaller).

Size preference and recall: Penis Size Preferences

After completing the immediate recall task, participants answered 15 questions about their penis size preferences. Each involved picking one penis size model from amongst the 33 models available. The option “No answer” also was available for each. For this study, the key questions were to select the model that they believed best reflected the average of men, which size is most likely to carry a sexually transmitted infection, and which size she would prefer for different expected relationship durations. The questions about preferences for different types of partners were a bit more complex. For one-time partners the question was:

“Imagine you're single and you're out at a restaurant with some friends. You meet an attractive man who is also single. He seems kind, intelligent, funny, and has a great job. You are feeling sexually aroused. He says he's in town for a conference but he has to fly back home tomorrow afternoon. If you could spend only this one night with him, what size would you want him to be?”

For long-term partners the question was: “What would be the ideal size for a husband or serious, long-term boyfriend?” The question regarding shorter-term partners clearly included much more detail. This was done in an attempt to control for intervening variables not of interest. For example, if a woman doubted at all for her safety with an unknown partner, she might select smaller models in the event of sexual assault. Thus, safety cues were included in the characterization.

Data analyses

Recall error was calculated as the difference of the dimension the participant chose minus the size of the actual sample. Thus, a positive number would indicate that participants chose a model larger than what they were shown. A within-participant ANOVA was calculated with the interaction of dimension (length, circumference) by recall (immediate, delayed. Put another way, the accuracy of recall could be affected by length or circumference being recalled better than the other dimension (dimension factor), by the length of the delay was until they selected a model (recall), or an interaction where length or circumference were recalled better at either the shorter or longer delay.

Descriptive data are provided regarding the size that women believed was average and the range women indicated for their “smallest” and “largest” sexual partner. To test whether women’s preferences differ by partner type, an ANOVA with dimension (length, circumference) X partner (one-time, long term) predicting preferred inches was conducted. A custom model was specified without dimension as a main effect, because dimensions were stipulated to be different in the generation of the stimuli.

Results

Participant demographics and sexual experience

All participants (N = 75) were screened to report sexual attraction to men, and ranged in age from 18 to 65. They were California residents, mostly white or Asian, sexually experienced, currently in a sexual relationship, and had sex recently (see Table 1). Twenty-seven percent of women reported that they had ended a relationship due, in part, to a mismatch between their penis size preference and their partner’s penis size (see Table 1). More women cited that the penis was too small as a problem, rather than that the penis was too large. The length and circumference of the model that each woman believed best represented the “average” penis size is presented in Figs 3 and 4 shows every woman’s selection of the “smallest” and “largest” sexual partner with whom she had contact.

thumbnail
Fig 3. Size of model selected by women indicating the “average” penis size.

(N = 75, r = .48).

http://dx.doi.org/10.1371/journal.pone.0133079.g003

thumbnail
Fig 4. Largest and smallest penis experiences.

No evidence of ceiling or floor effects in women’s choices indicating their largest and smallest sexual partner’s penis size.

http://dx.doi.org/10.1371/journal.pone.0133079.g004

Recall accuracy

Most (N = 48) women selected the exactly correct model (in both length and circumference) at immediate recall (see Fig 5). About half (N = 31) of women selected exactly the correct model at delayed recall. There was a main effect of dimension predicting model selection error (F(1,73) = 11.6, p < .001, ηp2 = .14): participants slightly underestimated penis length after the recall interval (M = -0.18 inches or -0.46 cm error), but were very accurate recalling penis circumference (M = 0.02 inches or 0.05 cm error). There was no main effect of delay nor dimension X delay interaction despite high power (f = .1, r = .9, 1-β = .97). Given the high accuracy, analyses for preferences were conducted as planned.

thumbnail
Fig 5. Recalled sizes (immediate and delayed) slightly shorter than actual model with most picking exact model.

Note: “0” indicates the exact correct model was chosen. Positive values indicate that the selected model was larger than the target model.

http://dx.doi.org/10.1371/journal.pone.0133079.g005

Does the expected relationship duration affect penis size preference?

For the penis size preferences for one-time or long-term partners, 15 women indicated “No answer”. Analyses were conducted on the remaining participants (N = 60). There was a small main effect for expected relationship duration, F(1,59) = 4.4, p = .04, ηp2 = .07 (see Fig 6), such that participants preferred a slightly larger penis size in one-time (length = 6.4 inches or 16.3 cm, circumference = 5.0 inches or 12.7 cm) partners as compared to long-term partners (length = 6.3 inches or 16.0 cm, circumference = 4.8 inches or 12.2 cm). There was no interaction of dimension (length, circumference) and relationship duration. Using independent t-tests separately predicting length and circumference preferences for partner type resulted in a significant difference for the test of circumference (t(59) = 2.4, p = .02, d = .2) only. Women preferred a larger circumference in one-time partners (M(SD) = 5.0(.1)) relative to long-term partners (M(SD) = 4.8(.1)). As ANOVA corrects for multiple comparisons, it is a more appropriate statistical test for these data. These t-tests are noted for full disclosure of the analyses conducted. Only 16 women selected a model as “most likely to have an STI”, whereas most women declined to select a model. Of the women who did respond, the model selected as most likely to have an STI was significantly larger (M(SD) = 6.2(.3)) than the model women used to indicate their one-night stand (M(SD) = 5.8(.2)) preference, F(1,15) =, p = .01, ηp2 = .35. This finding did not vary by the dimension (length, circumference).

thumbnail
Fig 6. Preference for larger penis in one-time relative to long-term relationships.

http://dx.doi.org/10.1371/journal.pone.0133079.g006

Discussion

Women attended one session in the laboratory during which they completed questionnaires about their sexual history and selected among 3D erect penis models to indicate their size preferences for one-time or longer-term partners. The state-space appeared to well-characterize the range of women’s experience, as their “largest” and “smallest” partners did not show evidence of ceiling or floor effects. Women tended to recall the size of the 3D models very well, only underestimating penis length. Women preferred a larger penis size (especially a larger circumference) for one-time partners as compared to long-term partners. While this preference for a larger phallus is above the average penis size, it is only very slightly above the average. While most declined to identify a penis size most likely to carry an STD, women selected even larger phallus sizes as the most likely to be infected with an STD.

A delay in model recall did not significantly worsen participant’s recall of the model size. In fact, women were generally very accurate in identifying the same model at both immediate and delayed recall. When they did make errors, they slightly underestimated model length. One possible explanation is that women care more about circumference, so they may attend to it more [63]. Some authors have argued that penis length actually is more important and “healthy” to desire than circumference (e.g., [64, 65]), but others have not replicated this reported pattern.

These data are generally consistent with Mautz et al. (2013), which asked women to rate the attractiveness of life-sized, projected, rotating drawings of male figures with flaccid penises of various sizes. Their participants preferred phalluses 2SD above their estimated population-average penis size, whereas our participants preferred penises that were only a little above average. This difference may be due to their images depicting flaccid penises, whereas our models depicted erect penises.

Since women’s preferences for both relationship types were slightly larger than the average male, the preferred size for the one-time partner was farther from the average. Novelty itself contributes to pleasure [66], so seeking a more novel-sized penis may be consistent with a goal to pursue pleasure primarily in one-time partners. Women may prefer a smaller penis size in a long-term partner compared to a one-time partner for reasons of both physical comfort and a preference for less masculinity in a longer term partner [67]. The difference in pleasure motive is also suggested by genital physiology. A larger circumference might stretch the vaginal opening such that the deep structures (clitoral crura and vestibular bulbs) are more stimulated, and the clitoral glans is more stimulated by penis movement [68]. Also, the vagina is densely packed with pressure-sensitive mechanoreceptors that detect stretch sensations [69]. These appear finely tuned to detect variability in circumference, whereas the vagina is less sensitive to differences in other stimuli such as vibration or warmth [70]. Other studies also found that women prefer a relatively larger penis proportional to body size [31], especially with respect to circumference (e.g., [54]). Given that women typically experience more pleasurable and orgasmic sex in longer-term relationships [71], they might prefer a larger penis for short-term sex partly so the increased physical sensation compensates for the reduced psychological connection. In one notable exception, a preference for general body somatotype did not differ by the relationship duration [brief uncommitted versus long-term partners in 72].

A larger penis could contribute to infection risks, such that a larger penis on more risky one-time partners elevates risk. A larger penis has been associated with higher infection rates amongst men who have sex with men [73]. Also, an increase in friction during intercourse from a condom is associated with the introduction of more bacteria into the vagina [74, 75] and more vulvar erythema [74]. Finally, women report that condoms increase their experience of pain during intercourse [76, 77]. Anything that increases friction during intercourse may promote genital injury, indirectly increasing infection risk. A larger phallus would increase friction relative to a smaller phallus. These potential complications of a larger penis suggest why the human penis has not evolved to be larger.

Individual differences among the women were not examined in relationship to their penis size preferences, although various female traits could interact with their sexual health risks. For example, women with wider hips tend to have a higher proportion of one-time sexual partners [78]. While women’s vaginal depth and pelvic muscle tonicity has been characterized [79, 80], these traits have never been related to women’s penis size preferences. Presumably, given the variability in vaginal size and tonicity, some women would experience more tearing with a larger phallus than other depending on the morphology of their particular vagina.

Generating haptic stimuli was relatively cost-effective and simple. Free software was available for generating print files. Also, the print files are shared online to allow exact future replications. Undergraduate research assistants were able to create and monitor the work flow. The 3D printer used is now widely, cheaply commercially available. Expanding this model into preferences pertaining to other domains, or even for other penis shape preferences, appears desirable.

As a first study using life-sized 3D models of erect penises to investigate preferences, some limitations exist. Models were not perfectly ecologically valid. They were blue to minimize racial skin-color cues. They were made with rigid, odorless plastic. They were a simplified dome-on-cylinder form rather than realistically shaped and textured. The male body was neither described nor portrayed. There were also limitations of self-report approaches. Men and women appear to have actually become less approving of one-time sexual partners since 2001 [81], which may affect the preferences that they are willing to report regarding such partners. Also, a significant minority (15 of 75) of women chose not to report a preference for penis size in short and long term partners, but did answer both of the recall questions. Perhaps these women did not have a clear preference, consistent with weak penis size preferences reported in some previous studies [54, 65]. This could be viewed as a strength, insofar as women did not feel compelled to answer in cases where they did not feel they had a strong enough basis to generate an answer.

Another limitation is sexual inexperience among some participants. Fifteen women in our sample indicated that they had never experienced sexual intercourse. This inexperience could underlie some of the size preferences observed. For example, women generally anticipate more pain with their first intercourse than they actually experience [82], so they may show risk-averse penis size preferences (for shorter length and thinner circumference than they may prefer with experience). Less experienced women may also be less accurate in their size estimates. However, a follow-up analysis showed that having had sexual intercourse (yes or no) did not predict penis size preferences, arguing against this possibility. A related limitation is that the experimental protocol necessarily limited the sample size, and these women were recruited largely near a college campus. There may be other biases in the sample related to the recruitment method and sample size that were not identified.

There are several implications of these data for males interested in long-term female partners. Males with a larger penis may be at an advantage when pursuing short-term female partners. Also, this study provides the first data on the accuracy of women’s penis size judgments. Furthermore, women tended to slightly underestimate the length of penis models after a recall delay. Women may misremember specific partners penis attributes as smaller than they really are. This may exacerbate men’s anxieties about their penis size. Men dissatisfied with their penis size have historically benefitted more from counseling than from surgically increasing their penis size [83]. This may help explain why most men seeking surgical interventions for enlarging what they perceive to be a small penis actually have a penis that falls within a normal range [16]. Finally, 3D printing allows greater flexibility and complexity in stimuli and highly accurate replications. This first use of 3D stimuli to assess preferences is promising. Increasing print resolution and animation will broaden the research applications with haptic stimuli.

Acknowledgments

The authors would like to thank numerous research assistants at University of California, Los Angeles for their assistance with data collection. We also thank Ardershir Rahman for assistance with model design and printing.

Author Contributions

Conceived and designed the experiments: NP GM. Performed the experiments: NP JP SL. Analyzed the data: NP JP SL GM. Contributed reagents/materials/analysis tools: NP. Wrote the paper: NP JP SL GM.

References

  1. 1. Tiggemann M, Martins Y, Churchett L. Beyond muscles: Unexplored parts of men's body image. Journal of Health Psychology. 2008;13(8):1163–72. doi: 10.1177/1359105308095971. pmid:18987089
  2. 2. Cheng PK, Chanoine JP. Should the Definition of Micropenis Vary According to Ethnicity? Hormone Research in Paediatrics. 2001;55(6):278–81. doi: 10.1159/000050013
  3. 3. Choi IH, Kim KH, Jung H, Yoon SJ, Kim SW, Kim TB. Second to fourth digit ratio: a predictor of adult penile length. Asian Journal of Andrology. 2011;13:710–4. doi: 10.1038/aja.2011.75. pmid:21725330
  4. 4. Shalaby ME, Almohsen AERM, El Shahid AR, Abd Al-Sameaa MT, Mostafa T. Penile length—somatometric parameters relationship in healthy Egyptian men. Andrologia. 2014:n/a–n/a. doi: 10.1111/and.12275.
  5. 5. Siminoski K, Bain J. The relationships among height, penile length, and foot size. Annals of Sex Research. 1993;6(3):231–5. doi: 10.1007/bf00849563.
  6. 6. Ponchietti R, Mondaini N, Bonafe M, Di Loro F, Biscioni S, Masieri L. Penile length and circumference: a study on 3,300 young Italian males. European urology. 2001;39(2):183–6. Epub 2001/02/27. 52434. pmid:11223678. doi: 10.1159/000052434
  7. 7. Soylemez H, Atar M, Sancaktutar AA, Penbegul N, Bozkurt Y, Onem K. Relationship between penile size and somatometric parameters in 2276 healthy young men. Int J Impot Res. 2012;24(3):126–9. doi: 10.1038/ijir.2011.53. pmid:22189447
  8. 8. Shah J, Christopher N. Can shoe size predict penile length? BJU International. 2002;90(6):586–7. doi: 10.1046/j.1464-410X.2002.02974.x. pmid:12230622
  9. 9. Schneider T, Sperling H, Lümmen G, Syllwasschy J, Rübben H. Does penile size in younger men cause problems in condom use? a prospective measurement of penile dimensions in 111 young and 32 older men. Urology. 2001;57(2):314–8. http://dx.doi.org/10.1016/S0090-4295(00)00925-0. pmid:11182344
  10. 10. Johnston L, McLellan T, McKinlay A. (Perceived) Size really does matter: Male dissatisfaction with penis size. Psychology of Men and Masculinity. 2014;15(2):225–8. doi: 10.1037/a0033264
  11. 11. Peter J, Valkenburg PM. Does exposure to sexually explicit Internet material increase body dissatisfaction? A longitudinal study. Computers in Human Behavior. 2014;36(0):297–307. http://dx.doi.org/10.1016/j.chb.2014.03.071.
  12. 12. Kvalem IL, Træen B, Lewin B, Štulhofer A. Self-perceived effects of Internet pornography use, genital appearance satisfaction, and sexual self-esteem among young Scandinavian adults. Cyberpsychology: Journal of Psychosocial Research on Cyberspace. 2014;8(4). doi: 10.5817/CP2014-4-4.
  13. 13. Veale D, Eshkevari E, Read J, Miles S, Troglia A, Phillips R, et al. Beliefs about Penis Size: Validation of a Scale for Men Ashamed about Their Penis Size. The Journal Of Sexual Medicine. 2014;11(1):84–92. doi: 10.1111/jsm.12294. pmid:24118940
  14. 14. Nabil N, Hosny H, Kadah A, Shamloul R. Evaluation of Surgical Outcome of Penile Augmentation and Lengthening Procedures. Urologia internationalis. 2013;90(4):465–9. doi: 10.1159/000347044. pmid:23548799
  15. 15. Kang D, Chung J, Kim Y, Lee H, Cho S, Chang T, et al. Efficacy and Safety of Penile Girth Enhancement by Autologous Fat Injection for Patients with Thin Penises. Aesth Plast Surg. 2012;36(4):813–8. doi: 10.1007/s00266-012-9891-4.
  16. 16. Mondaini N, Ponchietti R, Gontero P, Muir GH, Natali A, Di Loro F, et al. Penile length is normal in most men seeking penile lengthening procedures. International Journal of Impotence Research. 2002;14(4):283. doi: 10.1038/sj.ijir.3900887
  17. 17. Herbenick D, Schick V, Reece M, Sanders SA, Fortenberry JD. The Development and Validation of the Male Genital Self-Image Scale: Results from a Nationally Representative Probability Sample of Men in the United States. The Journal Of Sexual Medicine. 2013;10(6):1516–25. doi: 10.1111/jsm.12124. pmid:23551571
  18. 18. Althof SE, Cappelleri JC, Shpilsky A, Stecher V, Diuguid C, Sweeney M, et al. Treatment responsiveness of the Self-Esteem And Relationship questionnaire in erectile dysfunction. Urology. 2003;61(5):888–92. Epub 2003/05/09. pmid:12735997. doi: 10.1016/s0090-4295(03)00041-4
  19. 19. Lawrance K-A, Byers ES. Sexual satisfaction in long-term heterosexual relationships: The interpersonal exchange model of sexual satisfaction. Personal Relationships. 1995;2(4):267–85. doi: 10.1111/j.1475-6811.1995.tb00092.x.
  20. 20. Li NP, Kenrick DT. Sex similarities and differences in preferences for short-term mates: What, whether, and why. Journal of Personality and Social Psychology. 2006;90(5):468–89. Epub 3. doi: 10.1037/0022-3514.90.3.468
  21. 21. Royer HR, Falk EC, Heidrich SM. Genital Herpes Beliefs: Implications for Sexual Health. Journal of Pediatric and Adolescent Gynecology. 2013;26(2):109–16. http://dx.doi.org/10.1016/j.jpag.2012.11.007. doi: 10.1016/j.jpag.2012.11.007. pmid:23337309
  22. 22. Jonason PK, Li NP, Richardson J. Positioning the Booty-Call Relationship on the Spectrum of Relationships: Sexual but More Emotional Than One-Night Stands. The journal of sex research. 2010;48(5):486–95. doi: 10.1080/00224499.2010.497984.
  23. 23. Kissinger P, White S, Schmidt N, Taylor SN, Mena L, Lillis R, et al. O07.1 Sexual Relationship Importance and Condom Use Among Men Attending STD Clinics in Two Southern Cities in the United States. Sexually transmitted infections. 2013;89(Suppl 1):A38. doi: 10.1136/sextrans-2013-051184.0119.
  24. 24. Loewenstein GF, Weber EU, Hsee CK, Welch N. Risk as feelings. Psychological Bulletin. 2001;127(2):267–86. pmid:11316014 doi: 10.1037/0033-2909.127.2.267
  25. 25. Zink T, Fargo JD, Baker RB, Buschur C, Fisher BS, Sommers MS. Comparison of Methods for Identifying Ano-Genital Injury After Consensual Intercourse. The Journal of Emergency Medicine. 2010;39(1):113–8. http://dx.doi.org/10.1016/j.jemermed.2008.08.024. doi: 10.1016/j.jemermed.2008.08.024. pmid:19217245
  26. 26. Anderson SL, Parker BJ, Bourguignon CM. Changes in genital injury patterns over time in women after consensual intercourse. Journal of Forensic and Legal Medicine. 2008;15(5):306–11. http://dx.doi.org/10.1016/j.jflm.2007.12.007. doi: 10.1016/j.jflm.2007.12.007. pmid:18511005
  27. 27. Johnston L, McLellan T, McKinlay A. (Perceived) Size Really Does Matter: Male Dissatisfaction With Penis Size. Psychology of Men & Masculinity. 2014:No Pagination Specified. doi: 10.1037/a0033264
  28. 28. Fisher WA, Branscombe NR, Lemery CR. The bigger the better? Arousal and attributional responses to erotic stimuli that depict different size penises. The journal of sex research. 1983;19(4):377–96. doi: 10.1080/00224498309551199.
  29. 29. Ernst MO, Banks MS. Humans integrate visual and haptic information in a statistically optimal fashion. Nature. 2002;415(6870):429–33. pmid:11807554 doi: 10.1038/415429a
  30. 30. Dixson BJ, Dixson AF, Li B, Anderson MJ. Studies of human physique and sexual attractiveness: Sexual preferences of men and women in China. American Journal of Human Biology. 2007;19(1):88–95. doi: 10.1002/ajhb.20584. pmid:17160976
  31. 31. Mautz BS, Wong BBM, Peters RA, Jennions MD. Penis size interacts with body shape and height to influence male attractiveness. Proceedings of the National Academy of Sciences. 2013. doi: 10.1073/pnas.1219361110.
  32. 32. Wessells H, Lue TF, McAninch JW. Penile Length in the Flaccid and Erect States: Guidelines for Penile Augmentation. The Journal Of Urology. 1996;156(3):995–7. http://dx.doi.org/10.1016/S0022-5347(01)65682-9. pmid:8709382
  33. 33. Sengezer M, Öztürk S, DevecI M. Accurate Method for Determining Functional Penile Length in Turkish Young Men. Annals of Plastic Surgery. 2002;48(4):381–5. pmid:12068220 doi: 10.1097/00000637-200204000-00008
  34. 34. Awwad Z, Abu-Hijleh M, Basri S, Shegam N, Murshidi M, Ajlouni K. Penile measurements in normal adult Jordanians and in patients with erectile dysfunction. Int J Impot Res. 2004;17(2):191–5. doi: 10.1038/sj.ijir.3901272
  35. 35. Furr KD. Penis size and magnitude of erectile change as spurious factors in estimating sexual arousal. Annals of Sex Research. 1991;4(3–4):265–79. 1992-43496-001 0843–4611,4,3–4,265–279,1991. doi: 10.1007/bf00850057
  36. 36. Udelson D, Park K, Sadeghi-Najed H, Salimpour P, Krane RJ, Goldstein I. Axial penile buckling forces vs Rigiscan radial rigidity as a function of intracavernosal pressure: Why Rigiscan does not predict functional erections in individual patients. International Journal of Impotence Research. 2000;11:327–39. doi: 10.1038/sj.ijir.3900443
  37. 37. Gaißert N, Wallraven C, Bülthoff HH. Visual and haptic perceptual spaces show high similarity in humans. Journal of Vision. 2010;10(11). doi: 10.1167/10.11.2.
  38. 38. Wallraven C, Bülthoff H, Waterkamp S, van Dam L, Gaißert N. The eyes grasp, the hands see: Metric category knowledge transfers between vision and touch. Psychonomic Bulletin & Review. 2014;21(4):976–85. doi: 10.3758/s13423-013-0563-4.
  39. 39. Yildirim I, Jacobs RA. Transfer of object category knowledge across visual and haptic modalities: Experimental and computational studies. Cognition. 2013;126(2):135–48. http://dx.doi.org/10.1016/j.cognition.2012.08.005. doi: 10.1016/j.cognition.2012.08.005. pmid:23102553
  40. 40. Lawson R. Recognizing familiar objects by hand and foot: Haptic shape perception generalizes to inputs from unusual locations and untrained body parts. Atten Percept Psychophys. 2014;76(2):541–58. doi: 10.3758/s13414-013-0559-1. pmid:24197503
  41. 41. Wallraven C. Touching on face space: Comparing visual and haptic processing of face shapes. Psychonomic Bulletin & Review. 2014;21(4):995–1002. doi: 10.3758/s13423-013-0577-y.
  42. 42. Gaißert N, Waterkamp S, Fleming RW, Bülthoff I. Haptic Categorical Perception of Shape. PLoS One. 2012;7(8):e43062. doi: 10.1371/journal.pone.0043062. pmid:22900089
  43. 43. Norman JF, Kappers AL, Beers A, Scott AK, Norman H, Koenderink J. Aging and the haptic perception of 3D surface shape. Atten Percept Psychophys. 2011;73(3):908–18. doi: 10.3758/s13414-010-0053-y. pmid:21264712
  44. 44. Khan S, Somani B, Lam W, Donat R. Establishing a reference range for penile length in Caucasian British men: a prospective study of 609 men. BJU International. 2012;109(5):740–4. doi: 10.1111/j.1464-410X.2011.10338.x. pmid:21711435
  45. 45. Gebhard P, Johnson AB. The Kinsey data: marginal tabulations of the 1938–1963 interviews. Philadelphia: WB Saunders, 1979.
  46. 46. Brody S, Weiss P. Vaginal Orgasm Is Associated with Vaginal (Not Clitoral) Sex Education, Focusing Mental Attention on Vaginal Sensations, Intercourse Duration, and a Preference for a Longer Penis. The Journal Of Sexual Medicine. 2010;7(8):2774–81. doi: 10.1111/j.1743-6109.2009.01469.x. pmid:19732304
  47. 47. Richters J, Gerofi J, Donovan B. Are condoms the right size(s)? A method for self-measurement of the erect penis. Venerology. 1995;8(2):77–81.
  48. 48. Herbenick D, Reece M, Schick V, Sanders SA. Erect Penile Length and Circumference Dimensions of 1,661 Sexually Active Men in the United States. The Journal Of Sexual Medicine. 2014;11(1):93–101. doi: 10.1111/jsm.12244. pmid:23841855
  49. 49. Lee AJ, Dubbs SL, Von Hippel W, Brooks RC, Zietsch BP. A multivariate approach to human mate preferences. Evolution and Human Behavior. 2014;35(3):193–203. http://dx.doi.org/10.1016/j.evolhumbehav.2014.01.003.
  50. 50. Evans S, Neave N, Wakelin D, Hamilton C. The relationship between testosterone and vocal frequencies in human males. Physiology & Behavior. 2008;93(4–5):783–8. http://dx.doi.org/10.1016/j.physbeh.2007.11.033.
  51. 51. Baskin LS, Sutherland RS, DiSandro MJ, Hayward SW, Lipschutz J, Cunha GR. The Effect of Testosterone on Androgen Receptors and Human Penile Growth. The Journal Of Urology. 1997;158(3):1113–8. http://dx.doi.org/10.1016/S0022-5347(01)64400-8. pmid:9258152
  52. 52. Boas M, Boisen KA, Virtanen HE, Kaleva M, Suomi AM, Schmidt IM, et al. Postnatal penile length and growth rate correlate to serum testosterone levels: a longitudinal study of 1962 normal boys. European journal of endocrinology / European Federation of Endocrine Societies. 2006;154(1):125–9. Epub 2005/12/31. doi: 10.1530/eje.1.02066 pmid:16382001.
  53. 53. Eisenman R. Penis size: Survey of female perceptions of sexual satisfaction. BMC women's health. 2001;1(1):1. Epub 2001/06/21. pmid:11415468; PubMed Central PMCID: PMC33342.
  54. 54. Francken AB, van de Wiel HBM, van Driel MF, Weijmar Schultz WCM. What Importance Do Women Attribute to the Size of the Penis? European urology. 2002;42(5):426–31. http://dx.doi.org/10.1016/S0302-2838(02)00396-2. pmid:12429149
  55. 55. Lykins AD, Meana M, Strauss GP. Sex differences in visual attention to erotic and non-erotic stimuli. Archives of Sexual Behavior. 2008;37(2):219–28. pmid:17668312 doi: 10.1007/s10508-007-9208-x
  56. 56. Nummenmaa L, Hietanen J, Santtila P, Hyönä J. Gender and Visibility of Sexual Cues Influence Eye Movements While Viewing Faces and Bodies. Archives of Sexual Behavior. 2012;41(6):1439–51. doi: 10.1007/s10508-012-9911-0. pmid:22402995
  57. 57. Lang PJ, Bradley MM, Cuthbert BN. International affective picture system (IAPS): Affective ratings of pictures and instruction manual. Technical Report A-8. Gainesville, FL: University of Florida, 2008.
  58. 58. Backman K, Mononen M. Tinkercad. Available: https://tinkercad.com/about/2011.
  59. 59. Hoeken Z, Kintel M, Mayer A, Mets M. ReplicatorG. 2012.
  60. 60. Locke SD, Gilbert BO. Method of psychological assessment, self-disclosure, and experiential differences: A study of computer, questionnaire, and interview assessment formats. Journal of Social Behavior & Personality. 1995;10(1):255–63.
  61. 61. Spector I, Carey M, Steinberg L. The Sexual Desire Inventory: Development, factor structure, and evidence of reliability. Journal of Sex & Marital Therapy. 1996;22(3):175–90. doi: 10.1080/00926239608414655
  62. 62. Simpson JA, Gangestad SW. Individual differences in sociosexuality: Evidence for convergent and discriminant validity. Journal of Personality & Social Psychology. 1991;60(6):870–83. 1991-26250-001 0022–3514,60,6,870–883,1991. doi: 10.1037//0022-3514.60.6.870
  63. 63. Francken AB, van de Wiel HB, van Driel MF, Weijmar Schultz WC. What importance do women attribute to the size of the penis? European urology. 2002;42(5):426–31. Epub 2002/11/14. pmid:12429149. doi: 10.1016/s0302-2838(02)00396-2
  64. 64. Francken AB, van de Wiel HBM, Van Driel MF, & Weijmar Schultz WCMW. What importance do women attribute to size of the penis? European urology. 2002;42:426–31. pmid:12429149 doi: 10.1016/s0302-2838(02)00396-2
  65. 65. Štulhofer A. How (Un)Important Is Penis Size for Women with Heterosexual Experience? Archives of Sexual Behavior. 2006;35(1):5–6. doi: 10.1007/s10508-006-8989-7. pmid:16502148
  66. 66. Bunzeck N, Doeller CF, Dolan RJ, Duzel E. Contextual interaction between novelty and reward processing within the mesolimbic system. Human Brain Mapping. 2012;33(6):1309–24. doi: 10.1002/hbm.21288. pmid:21520353
  67. 67. Little AC, Jones BC, Penton-Voak IS, Burt DM, Perrett DI. Partnership status and the temporal context of relationships influence human female preferences for sexual dimorphism in male face shape. Proceedings of the Royal Society of London Series B: Biological Sciences. 2002;269(1496):1095–100. doi: 10.1098/rspb.2002.1984. pmid:12061950
  68. 68. Wallen K, Lloyd EA. Female sexual arousal: Genital anatomy and orgasm in intercourse. Hormones and Behavior. 2011;59(5):780–92. http://dx.doi.org/10.1016/j.yhbeh.2010.12.004. doi: 10.1016/j.yhbeh.2010.12.004. pmid:21195073
  69. 69. Berman JR, Adhikari SP, Goldstein I. Anatomy and physiology of female sexual function and dysfunction: classification, evaluation and treatment options. European urology. 2000;38(1):20–9. pmid:10859437. doi: 10.1159/000020247
  70. 70. Vardi Y, Gruenwald I, Sprecher E, Gertman I, Yartnitsky D. Normative values for female genital sensation. Urology. 2000;56(6):1035–40. pmid:11113756 doi: 10.1016/s0090-4295(00)00850-5
  71. 71. Armstrong EA, England P, Fogarty ACK. Accounting for Women’s Orgasm and Sexual Enjoyment in College Hookups and Relationships. American Sociological Review. 2012;77(3):435–62. doi: 10.1177/0003122412445802
  72. 72. Dixson BJ, Grimshaw GM, Ormsby DK, Dixson AF. Eye-tracking women’s preferences for men’s somatotypes. Evolution and Human Behavior. 2014;35(2):73–9. http://dx.doi.org/10.1016/j.evolhumbehav.2013.10.003.
  73. 73. Grov C, Parsons J, Bimbi D. The Association Between Penis Size and Sexual Health Among Men Who Have Sex with Men. Archives of Sexual Behavior. 2010;39(3):788–97. doi: 10.1007/s10508-008-9439-5. pmid:19139986
  74. 74. Eschenbach DA, Patton DL, Hooton TM, Meier AS, Stapleton A, Aura J, et al. Effects of Vaginal Intercourse with and without a Condom on Vaginal Flora and Vaginal Epithelium. Journal of Infectious Diseases. 2001;183(6):913–8. doi: 10.1086/319251. pmid:11237808
  75. 75. Soper DE, Brockwell NJ, Dalton HP. Evaluation of the effects of a female condom on the female lower genital tract. Contraception. 1991;44(1):21–9. http://dx.doi.org/10.1016/0010-7824(91)90103-M. pmid:1893699
  76. 76. Crosby R, Milhausen R, Mark K, Yarber W, Sanders S, Graham C. Understanding Problems with Condom Fit and Feel: An Important Opportunity for Improving Clinic-Based Safer Sex Programs. J Primary Prevent. 2013;34(1–2):109–15. doi: 10.1007/s10935-013-0294-3.
  77. 77. Fennell J. “And Isn't that the point?”: pleasure and contraceptive decisions. Contraception. 2014;89(4):264–70. http://dx.doi.org/10.1016/j.contraception.2013.11.012. doi: 10.1016/j.contraception.2013.11.012. pmid:24332430
  78. 78. Simpson V, Brewer G, Hendrie C. Evidence to Suggest that Women’s Sexual Behavior is Influenced by Hip Width Rather than Waist-to-Hip Ratio. Archives of Sexual Behavior. 2014:1–5. doi: 10.1007/s10508-014-0289-z.
  79. 79. Barnhart KT, Izquierdo A, Pretorius ES, Shera DM, Shabbout M, Shaunik A. Baseline dimensions of the human vagina. Human Reproduction. 2006;21(6):1618–22. doi: 10.1093/humrep/del022. pmid:16478763
  80. 80. Pendergrass PB, Belovicz MW, Reeves CA. Surface Area of the Human Vagina as Measured from Vinyl Polysiloxane Casts. Gynecologic and Obstetric Investigation. 2003;55(2):110–3. pmid:12771458 doi: 10.1159/000070184
  81. 81. Prah P, Copas AJ, Mercer CH, Clifton S, Erens B, Phelps A, et al. Consistency in reporting sensitive sexual behaviours in Britain: change in reporting bias in the second and third National Surveys of Sexual Attitudes and Lifestyles (Natsal-2 and Natsal-3). Sexually transmitted infections. 2013. doi: 10.1136/sextrans-2013-051360.
  82. 82. Weis DL. The experience of pain during women's first sexual intercourse: Cultural mythology about female sexual initiation. Archives of Sexual Behavior. 1985;14(5):421–38. pmid:4062539 doi: 10.1007/bf01542003
  83. 83. Nugteren HM, Balkema GT, Pascal AL, Schultz WCMW, Nijman JM, van Driel MF. 18-Year Experience in the Management of Men With a Complaint of a Small Penis. Journal of Sex & Marital Therapy. 2010;36(2):109–17. doi: 10.1080/00926230903554438.