The organization of sexual preferences

Arfer, Kodi B.; Eaton, Nicholas R.

Introduction

What kinds of sexual activities and sexual partners are people attracted to? As in all domains of human life, such as food, movies, and academic disciplines, there are widespread individual differences in what people like. The diversity of people's "sexual preferences"—by which we mean preferences concerning sexual activity, whether for particular kinds of partners, particular sexual acts, or even moods or themes, such as vulnerability or purity—is perhaps most obvious from surveys of Internet pornography (e.g., Ogas & Gaddam, 2011) and Internet communities devoted to particular sexual interests (e.g., Scorolli, Ghirlanda, Enquist, Zattoni, & Jannini, 2007) or even the lack of sexual interests (Chasin, 2011). It seems reasonable to expect that preferences will be interrelated; for example, people who are interested in dominance or submission might also be interested in sexual scenes involving bondage or leather. How, then, are sexual preferences organized? In other words, how are sexual preferences related to each other?

In research and popular discourse, sexual preferences are typically organized around sexual orientations, which, in turn, are typically construed in terms of partner gender and discrete categories. Debate continues on exactly which sexual orientations exist (Rosenthal, Sylva, Safron, & Bailey, 2012; Savin-Williams & Vrangalova, 2013; Kuper, Nussbaum, & Mustanski, 2012; Bogaert, 2006; Seto, 2012). Other controversy includes whether discrete orientation categories should be replaced with continuous scales (Ellis, Burke, & Ames, 1987; Haslam, 1997) and whether continuous variation exists on top of latent discrete categories (Gangestad, Bailey, & Martin, 2000).

While there is debate over the details of how to conceptualize sexual orientation, we see two fundamental issues that have rarely been addressed. First, focusing on sexual orientation means focusing on the features of a prospective sexual partner, and usually only one feature, namely, the partner's gender. One does not have the opportunity to consider preferences for less concrete partner features, such as personality or social status, nor different sexual activities, such as masturbation or anal sex, nor moods or themes, such as BDSM. People with the same sexual orientation need not agree on any of these. Second, the construct of sexual orientation has not been developed in an integrative empirical fashion with the idea of finding structure underlying the totality of people's preferences. By contrast, consider research into personality, intelligence, and psychopathology. Personality researchers have found that hundreds or thousands of descriptive terms can be reduced to a few personality traits (Goldberg, 1990). Intelligence researchers have found a single dimension of fluid intelligence that can explain performance on a wide variety of tasks (Gottfredson, 1997). Psychopathology researchers have found that the many psychiatric symptoms people experience can be summarized with a few dimensions, such as internalizing, externalizing, and thought disorder (Kotov et al., 2017). Perhaps the whole universe of sexual preferences, too, can be characterized with such a coherent underlying structure.

In this study, we sought to bring a personality-inspired and statistically rich approach to the study of sexual preferences. We used a self-report form to survey preferences for a wide variety of characteristics of sexual acts and partners. We analyzed these items with two kinds of unsupervised statistical learning methods to search for underlying structure and show how different preferences are related to each other.

Method

See http://arfer.net/projects/galaxy for the deidentified raw data, task code (including the complete instrument), and data-analysis code.

Subjects

We recruited and ran subjects on Amazon Mechanical Turk (MTurk), a data-collection website, in April, May, and July of 2014. MTurk "workers" are ordinary Internet users aged 18 and above who volunteer to complete short unskilled online tasks for nominal fees. Increasingly, MTurk is being used by researchers to study human behavior. For example, Suri and Watts (2011) studied social networks, and Eriksson and Simpson (2010) examined gender differences in risk preferences. Evidence that MTurk can provide data comparable in quality to that produced in conventional laboratory settings is provided by studies such as Buhrmester, Kwang, and Gosling (2011), which replicated previous estimates of the retest reliability of several personality measures. While samples of Americans on MTurk are not random samples of the US population, they are likely to be more diverse (Ipeirotis, 2010), and therefore more representative of the US population, than the undergraduate subject pools used in most studies with human subjects. Moreover, we expected that subjects using an anonymous online platform would be more honest about their sexual preferences and less influenced by social desirability.

A total of 1,001 MTurk users completed the study. The study was described as "a survey about sexual feelings and sexual behavior". Subjects were required to live in the United States. The median completion time was 13 minutes. Subjects were compensated with $2.

Instrument

The items analyzed in this study were part of a larger questionnaire. Subjects were told "We would like you to consider how sexually appealing you find each of these activities." They were presented with a number of short descriptions and rated each on a 7-point scale with anchors "Not at all appealing" (1), "Somewhat appealing" (4), and "Very appealing" (7). There were 94 items in total, 9 of which were presented only to subjects who described their gender as "Male" and 5 of those who selected "Female". See the appendix for complete instructions and item text. The items were presented in a random order for each subject. In line with our focus on sexual preferences, instructions emphasized that subjects should "answer using only your sexual and romantic feelings", as opposed to considering whether they would actually be willing to perform a given activity (e.g., one cannot consent to being raped, by definition, but one could still enjoy a fantasy of such). Here is an outline of the various items.

Items 1–20 concern specific sexual acts such as masturbation, coitus, anal copulation, and oral sex.
Items 21–27 concern semen specifically.
Items 28–45 concern fetishes such as bondage, leather, and urine play. Also included are items about rape, both rape in general and sex with an unconscious person in particular.
Items 46–50 concern pornography.
Items 51–61 concern the relationship with a sex partner and feelings towards them.
Items 62–69 concern the size of partner body features such as the penis, breasts, and feet.
Items 70–80 concern the gender, gender typicality, and age of a partner.
Items 81–94 concern other partner features such as personality and sexual experience. The final ten items are based on the short Big Five personality test of Gosling, Rentfrow, and Swann (2003).

At the end of the questionnaire, two questions related to sexual preferences were repeated as validity items: one about fellating someone else and one about sex with a friend. A third validity item asked "How honest were you able to be while answering this survey? (We won't withhold payment based on your answer to this question.)" Subjects responded on a 5-point scale with anchors "Not at all honest", "Somewhat honest", and "Entirely honest".

Demographic questions (including items about gender, age, etc.) were asked at the beginning of the questionnaire. The gender item asked "What is your gender?" and had four fixed options—"Male", "Female", "Transgender (male-to-female)", and "Transgender (female-to-male)"—and a free-response option labeled "Other".

Analytic sample

To reduce the effect of careless responses on our results, we excluded subjects from analysis on the basis of response time and their responses to the three validity items in part 8. Subjects were excluded if they completed the task in less than 7 minutes (n = 46), they rated their honesty as "Somewhat honest" or less (n = 20), or their responses to both repeated items differed from their original responses by 3 units or more (n = 5). One subject was excluded because she said she had selected the wrong gender, meaning she had been asked the wrong preferences questions. Finally, since this study analyzes men and women separately, but without trying to distinguish the effects of anatomy, endocrinology, social role, gender identity, and so on, we excluded all subjects who chose an option for the gender item other than "Male" or "Female" (n = 15). The resulting analytic sample comprised 923 subjects.

Data analysis

We use two basic methods—clustering and factor analysis, similarly to Forbes et al. (2017)—to examine how the preference items are related to each other, and in particular, how they can be grouped. We try each approach separately within each sex.

The clustering approach is theoretically simple and requires no modeling or scale assumptions beyond the assumption of an ordinal scale for each item and independent sampling of subjects. Clustering is usually used to group cases (subjects), but we use it to group variables (items). We use agglomerative mean-linkage hierarchical clustering (function hclust in the R package stats) with the distance metric d(X, Y) = 1 − |k(X, Y)|, where k(X, Y) is the Kendall correlation of X with Y. We use Kendall correlation, a rank-based measure, to avoid having to assign meaning to the distance between points on each item's 7-point rating scale (to account for ties, R uses the τ_B metric of Kendall, 1945, which removes tied pairs from the quotient used to calculate τ). Mean-linkage hierarchical clustering proceeds iteratively by first assigning every object to its own cluster, so there are q clusters for q objects. Then, for every pair of clusters A and B, the mean of the pairwise distances between objects in A and B is computed, and the two clusters with the least such mean are combined into one cluster, leaving q − 1 clusters. Clusters continue to be combined two at a time until all q objects are in a single cluster. Given our distance metric, each of our clusters is characterized by a mean absolute Kendall correlation. We present the results backwards, starting from the case of 1 cluster and describing the results for 2, 3, 4, 5, 6, and 7 clusters. The effect is that for each k, the analysis with k clusters has all the same clusters as the analysis with k − 1 clusters, except that one of the old clusters has had items removed from it to form the new cluster.

Exploratory factor analysis is a method that is more familiar to social scientists but relies on concrete distributional assumptions about the data. We take a bass-ackwards approach (Goldberg, 2006), in which we fit a 2-factor solution, followed by a 3-factor solution, and so on up to 7 factors, with each solution as a separate model. We then save factor scores and compare them between levels. Each factor analysis (function fa in the R package psych) is fit with maximum likelihood estimation on a polychoric correlation matrix and uses orthogonal varimax rotation.

Clustering and factor analyses are not usually methods that are used to address the same problems. But by clustering variables, rather than clustering subjects, we make clustering, like factor analysis, an unsupervised way to see how variables can be grouped on the basis of their interrelations. The advantage of using both methods is that clustering is simple whereas factor analysis is complex. The interpretation of clusters does not depend on modeling assumptions such as the shape of items' distributions, but can only speak to relationships between items. Factor analysis relies on the strong assumption of the common-factor model, but it makes stronger claims, including a loading of each item on each factor, and a score of each subject on each factor.

Results

Demographics

Of the analytic sample, 459 subjects (50%) were female. Ages ranged from 18 to 82 (median 31). Subjects were 80% white, 10% black, 8% Asian, 6% Hispanic, and 2% Native American (they were allowed to select more than one of these categories). With regard to education, 12% had a graduate degree, 39% had an undergraduate degree, 37% had had some college education, 11% had graduated from high school, and the remaining 1% had not completed high school. The median annual-income category was $20,000 to $29,999. Most subjects (97%) identified as native speakers of English, and the remainder as fluent non-native speakers of English.

Men's preferences

The cluster analysis for men is shown in Table 1. See Figure 1 for a dendrogram. The initial cluster of all items could be characterized as interest in men, going by the items with the greatest mean absolute correlation. Of the other clusters, all but cluster 6 form by removing items directly from cluster 1. Cluster 2 does not have an obvious interpretation—it seems to characterize interest in a partner with personality traits that are typically undesirable. It may be related to subjects' lack of concern for partner personality. Cluster 3 concerns interest in women. Cluster 4 comprises mildly socially proscribed items (kink) such as voyeurism and bondage. Cluster 5 comprises strongly proscribed items, where consent is lacking or expected to be lacking, including rape, incest, and sex with children (including teenagers). Cluster 6 is a single-item cluster, containing the item about sex with a virgin, which is taken from cluster 4. Finally, cluster 7 contains two items: sex with a masculine woman and sex with a 70-year-old. In order, the seven clusters can be described as: men, unpersonability, women, kink, nonconsent, virginity, and unusual partners.

Table 1. Clusters of men's sexual preferences. Shown are the top five items of each cluster (columns) in each stage of clustering (row groups), scored by mean absolute Kendall correlation with all other items in the cluster. The top of each cluster shows the total number of items in the cluster (q) as well as the mean and SD of all pairwise absolute Kendall correlations. For every cluster in this table, the sign of the correlation of the top item with the lower four items is positive.
1 (Men)	2 (Unpersonability)	3 (Women)	4 (Kink)	5 (Nonconsent)	6 (Virginity)	7 (?)
q 89, M .14, SD .13
.21 Man
.21 Penis in man's anus
.21 Fellating
.20 Swallowing semen
.20 Masturbating a man
q 80, M .15, SD .13	q 9, M .24, SD .09
.23 Man	.28 Non-open partner
.23 Penis in man's anus	.26 Unconscientious partner
.22 Fellating	.24 Small buttocks
.22 Swallowing semen	.24 Neurotic partner
.22 Masturbating a man	.24 Introverted partner
q 56, M .19, SD .16	q 9, M .24, SD .09	q 24, M .22, SD .11
.28 Man	.28 Non-open partner	.29 Masturbating a woman
.28 Penis in man's anus	.26 Unconscientious partner	.28 Coitus
.28 Fellating	.24 Small buttocks	.27 Giving pleasure
.28 Swallowing semen	.24 Neurotic partner	.27 Feminine woman
.27 Masturbating a man	.24 Introverted partner	.25 Sex in relationship
q 25, M .35, SD .24	q 9, M .24, SD .09	q 24, M .22, SD .11	q 31, M .21, SD .10
.50 Man	.28 Non-open partner	.29 Masturbating a woman	.26 Voyeurism in secret
.49 Receiving semen in mouth	.26 Unconscientious partner	.28 Coitus	.26 Insulting
.48 Swallowing semen	.24 Small buttocks	.27 Giving pleasure	.25 Voyeurism in open
.48 Large penis	.24 Neurotic partner	.27 Feminine woman	.25 Tying up
.48 Fellating	.24 Introverted partner	.25 Sex in relationship	.25 Ejaculating into anus
q 19, M .50, SD .21	q 9, M .24, SD .09	q 24, M .22, SD .11	q 31, M .21, SD .10	q 6, M .30, SD .09
.62 Man	.28 Non-open partner	.29 Masturbating a woman	.26 Voyeurism in secret	.36 Raping
.60 Receiving semen in mouth	.26 Unconscientious partner	.28 Coitus	.26 Insulting	.34 Unconscious partner
.60 Large penis	.24 Small buttocks	.27 Giving pleasure	.25 Voyeurism in open	.30 14-year-old
.60 Fellating	.24 Neurotic partner	.27 Feminine woman	.25 Tying up	.28 Being raped
.59 Swallowing semen	.24 Introverted partner	.25 Sex in relationship	.25 Ejaculating into anus	.27 Incest
q 19, M .50, SD .21	q 9, M .24, SD .09	q 24, M .22, SD .11	q 30, M .22, SD .10	q 6, M .30, SD .09	q 1, M NaN, SD NaN
.62 Man	.28 Non-open partner	.29 Masturbating a woman	.26 Voyeurism in secret	.36 Raping	Virgin
.60 Receiving semen in mouth	.26 Unconscientious partner	.28 Coitus	.26 Insulting	.34 Unconscious partner
.60 Large penis	.24 Small buttocks	.27 Giving pleasure	.26 Voyeurism in open	.30 14-year-old
.60 Fellating	.24 Neurotic partner	.27 Feminine woman	.26 Tying up	.28 Being raped
.59 Swallowing semen	.24 Introverted partner	.25 Sex in relationship	.25 Ejaculating into anus	.27 Incest
q 17, M .58, SD .13	q 9, M .24, SD .09	q 24, M .22, SD .11	q 30, M .22, SD .10	q 6, M .30, SD .09	q 1, M NaN, SD NaN	q 2, M .25, SD .00
.67 Man	.28 Non-open partner	.29 Masturbating a woman	.26 Voyeurism in secret	.36 Raping	Virgin	.25 Masculine woman
.66 Receiving semen in mouth	.26 Unconscientious partner	.28 Coitus	.26 Insulting	.34 Unconscious partner		.25 70-year-old
.65 Large penis	.24 Small buttocks	.27 Giving pleasure	.26 Voyeurism in open	.30 14-year-old
.65 Swallowing semen	.24 Neurotic partner	.27 Feminine woman	.26 Tying up	.28 Being raped
.65 Fellating	.24 Introverted partner	.25 Sex in relationship	.25 Ejaculating into anus	.27 Incest

Figure 1. Dendrogram of the cluster analysis of men's sexual preferences. Height is defined such that among all the items grouped together below a given height `h`, every pair has an absolute Kendall correlation of at least 1 - `h`.

For factor analysis, we first count zero cells because of our use of polychoric correlation. Overall, 22% of all pairs of responses choices never occur; 96% of item pairs have at least one of these zeros in their frequency table. The factor analyses are depicted in Table 2 and Table 3. At level 1, when there is only one factor, the lone factor is driven by interest in men, particularly fellating another man. This factor reappears consistently in the subsequent analyses. At level 2, factor 2 is associated with interest in women, pornography, and insertive oral sex. At level 3, factor 2 resembles a kink factor more than a women factor, while the new factor 3 is related to tenderness, headed by a negative loading for sex with an 8-year-old. Level 4 restores the factor 2's focus on women and leaves factor 4 as a kink factor or a more general willingness to explore sexually. At level 5, factor 5 recalls the "undesirable personality traits" cluster from the cluster analysis. At level 6, factor 6 appears to concern nonmonogamous sex; its factor scores are highly correlated with those of the previous level's factor 5, and resembles the pornography cluster from the cluster analysis. Finally, factor 7 concerns the anus, especially women's anuses. In order, the seven factors can be described as: men, women, tenderness, kink, undesirable personality traits, nonmonogamy, and the female anus.

Table 2. Factor analyses of men's sexual preferences. Shown are the top five items of each factor (columns) in each factor analysis (row groups), scored by factor loading (which is sorted by absolute value).
1 (Men)	2 (Women)	3 (Tenderness)	4 (Kink)	5 (Unpersonability)	6 (Nonmonogamy)	7 (Female Anus)
—
.96 Man
.95 Receiving semen in mouth
.94 Large penis
.94 Fellating
.93 Swallowing semen
—	—
.96 Man	.67 Ejaculating into mouth
.94 Receiving semen in mouth	.65 Porn video, male-female
.94 Fellating	.64 Masturbating a woman
.94 Large penis	.62 Penis in woman's anus
.93 Swallowing semen	.62 Porn video, female-female
—	—	—
.97 Man	.70 Penis in woman's anus	-.77 8-year-old
.95 Fellating	.69 Ejaculating into anus	.69 Giving pleasure
.95 Large penis	.64 Voyeurism in secret	.69 Sex in relationship
.94 Masculine man	.64 Insulting	.66 Being sexually desired
.94 Receiving semen in mouth	.63 Acquaintance	.66 Feeling in love
—	—	—	—
.95 Man	.66 Giving cunnilingus	-.77 8-year-old	.73 Acquaintance
.94 Receiving semen in mouth	.61 Masturbating a woman	.67 Sex in relationship	.68 Stranger
.94 Fellating	.57 Coitus	.66 Giving pleasure	.68 Friend
.92 Large penis	.57 Ejaculating into vagina	.66 Feeling in love	.65 Controlling
.92 Swallowing semen	.57 Giving a woman anilingus	.64 Being sexually desired	.63 Insulting
—	—	—	—	—
.95 Man	.64 Giving cunnilingus	-.78 8-year-old	.65 Ejaculating into anus	.61 Non-open partner
.94 Receiving semen in mouth	.57 Masturbating a woman	.67 Giving pleasure	.65 Controlling	.60 Unconscientious partner
.94 Fellating	.54 Giving a woman anilingus	.67 Sex in relationship	.64 Insulting	.57 Neurotic partner
.92 Large penis	.54 Coitus	.66 Feeling in love	.64 Tying up	.53 Introverted partner
.91 Swallowing semen	.53 Woman	.65 Being sexually desired	.63 Ejaculating into mouth	.50 Disagreeable partner
—	—	—	—	—	—
.95 Man	.63 Giving cunnilingus	.72 Feeling in love	.63 Receiving pain	.62 Non-open partner	.70 Acquaintance
.93 Receiving semen in mouth	.58 Masturbating a woman	.69 Sex in relationship	.63 Tying up	.58 Unconscientious partner	.70 Ejaculating into mouth
.93 Fellating	.58 Woman	.68 Emotional closeness	.62 Being tied up	.57 Neurotic partner	.69 Stranger
.92 Large penis	.57 Coitus	.65 Kissing	.57 Causing pain	.52 Introverted partner	.68 Group sex
.91 Swallowing semen	.56 Ejaculating into vagina	.64 Giving pleasure	.55 Controlling	.50 Disagreeable partner	.68 Friend
—	—	—	—	—	—	—
.96 Man	.54 Giving cunnilingus	.73 Feeling in love	.73 Being tied up	.64 Non-open partner	.69 Acquaintance	.82 Ejaculating into anus
.94 Fellating	.53 Woman	.70 Sex in relationship	.68 Receiving pain	.58 Unconscientious partner	.68 Friend	.73 Penis in woman's anus
.94 Receiving semen in mouth	.52 Masturbating a woman	.68 Emotional closeness	.64 Being controlled	.56 Neurotic partner	.68 Group sex	.59 Giving a woman anilingus
.93 Large penis	.51 Coitus	.65 Giving pleasure	.61 Tying up	.55 Introverted partner	.67 Ejaculating into mouth	.44 Receiving anilingus
.92 Masturbating a man	.47 Feminine woman	.64 Kissing	.59 Being insulted	.53 Large feet	.67 Stranger	.33 Ejaculating into mouth

Table 3. Correlation of factor scores for men's sexual preferences, between factors at each level of the bass-ackwards procedure (rows) with those at the previous level (columns). Off-diagonal elements with absolute value of 1/3 or more are in bold.
	1	2	3	4	5	6
	—
1	.99
2	-.29
	—	—
1	.98	-.24
2	.12	.83
3	-.53	.61
	—	—	—
1	.99	.07	-.39
2	-.12	.56	-.00
3	-.38	-.00	.99
4	-.06	.86	.27
	—	—	—	—
1	.99	.02	-.39	-.12
2	.08	.99	-.08	-.02
3	-.40	-.02	.99	.23
4	-.05	.17	.18	.94
5	.07	.03	-.06	.36
	—	—	—	—	—
1	.99	.06	-.39	-.09	.07
2	.01	.98	.03	.09	.01
3	-.35	-.04	.95	.17	-.08
4	.26	.23	-.48	.47	-.06
5	.13	.05	-.20	-.02	.97
6	-.27	-.08	.56	.82	.11
	—	—	—	—	—	—
1	.99	-.02	-.36	.24	.13	-.25
2	.10	.91	-.02	-.01	.15	-.05
3	-.36	.03	.99	-.27	-.16	.40
4	.19	.00	-.19	.93	.15	-.13
5	.10	-.00	-.16	.15	.96	-.04
6	-.23	.05	.38	-.11	-.05	.99
7	.03	.48	-.11	.39	-.20	.11

Women's preferences

The cluster analysis for women is shown in Table 4. See Figure 2 for a dendrogram. The initial cluster is dominated by interest in women, similarly to how the initial cluster for men was dominated by interest in men. Cluster 2 concerns tenderness, such as sex in a committed relationship and intimacy; oddly, being masturbated by a partner appears here. Cluster 3 takes the now-familiar unpersonability group out of cluster 1. Cluster 4 concerns nonconsent, and is also formed from cluster 1. Cluster 5 takes a single item, sex with a 70-year-old person, out of cluster 3. Cluster 6 is the first appearance of a cluster for interest in men; it draws from cluster 1. Finally, cluster 7 removes body characteristics from cluster 3, including feet, small buttocks, and small penises. In order, the seven clusters can be described as: women, tenderness, nonconsent, senior partners, men, and small body parts.

Table 4. Clusters of women's sexual preferences. Shown are the top five items of each cluster (columns) in each stage of clustering (row groups), scored by mean absolute Kendall correlation with all other items in the cluster. The top of each cluster shows the total number of items in the cluster (q) as well as the mean and SD of all pairwise absolute Kendall correlations. For every cluster in this table, the sign of the correlation of the top item with the lower four items is positive.
1 (Women)	2 (Tenderness)	3 (Unpersonability)	4 (Nonconsent)	5 (Seniors)	6 (Men)	7 (Smallness)
q 85, M .15, SD .11
.22 Giving cunnilingus
.22 Group sex
.21 Woman
.21 Porn videos or pictures
.21 Porn video, female-female
q 73, M .17, SD .11	q 12, M .26, SD .10
.25 Giving cunnilingus	.31 Sex in relationship
.24 Group sex	.30 Emotional closeness
.23 Porn video, female-female	.29 Feeling in love
.23 Porn videos or pictures	.27 Giving pleasure
.23 Masturbating a woman	.27 Being sexually desired
q 61, M .20, SD .12	q 12, M .26, SD .10	q 12, M .18, SD .08
.27 Giving cunnilingus	.31 Sex in relationship	.22 Neurotic partner
.27 Group sex	.30 Emotional closeness	.22 Small feet
.26 Porn video, female-female	.29 Feeling in love	.21 Small buttocks
.26 Woman	.27 Giving pleasure	.21 Non-open partner
.26 Masturbating a woman	.27 Being sexually desired	.21 Unconscientious partner
q 55, M .21, SD .12	q 12, M .26, SD .10	q 12, M .18, SD .08	q 6, M .27, SD .11
.29 Giving cunnilingus	.31 Sex in relationship	.22 Neurotic partner	.31 14-year-old
.28 Group sex	.30 Emotional closeness	.22 Small feet	.30 Raping
.28 Porn video, female-female	.29 Feeling in love	.21 Small buttocks	.27 Incest
.28 Woman	.27 Giving pleasure	.21 Non-open partner	.27 Being raped
.27 Masturbating a woman	.27 Being sexually desired	.21 Unconscientious partner	.23 8-year-old
q 55, M .21, SD .12	q 12, M .26, SD .10	q 11, M .20, SD .08	q 6, M .27, SD .11	q 1, M NaN, SD NaN
.29 Giving cunnilingus	.31 Sex in relationship	.23 Small feet	.31 14-year-old	70-year-old
.28 Group sex	.30 Emotional closeness	.23 Neurotic partner	.30 Raping
.28 Porn video, female-female	.29 Feeling in love	.22 Small buttocks	.27 Incest
.28 Woman	.27 Giving pleasure	.22 Non-open partner	.27 Being raped
.27 Masturbating a woman	.27 Being sexually desired	.21 Unconscientious partner	.23 8-year-old
q 42, M .25, SD .12	q 12, M .26, SD .10	q 11, M .20, SD .08	q 6, M .27, SD .11	q 1, M NaN, SD NaN	q 13, M .26, SD .13
.35 Giving cunnilingus	.31 Sex in relationship	.23 Small feet	.31 14-year-old	70-year-old	.33 Fellating
.33 Woman	.30 Emotional closeness	.23 Neurotic partner	.30 Raping		.30 Receiving semen in mouth
.33 Masturbating a woman	.29 Feeling in love	.22 Small buttocks	.27 Incest		.29 Swallowing semen
.33 Porn video, female-female	.27 Giving pleasure	.22 Non-open partner	.27 Being raped		.29 Large penis
.31 Group sex	.27 Being sexually desired	.21 Unconscientious partner	.23 8-year-old		.29 Coitus
q 42, M .25, SD .12	q 12, M .26, SD .10	q 5, M .25, SD .08	q 6, M .27, SD .11	q 1, M NaN, SD NaN	q 13, M .26, SD .13	q 6, M .25, SD .08
.35 Giving cunnilingus	.31 Sex in relationship	.28 Neurotic partner	.31 14-year-old	70-year-old	.33 Fellating	.30 Small feet
.33 Woman	.30 Emotional closeness	.28 Unconscientious partner	.30 Raping		.30 Receiving semen in mouth	.27 Large feet
.33 Masturbating a woman	.29 Feeling in love	.26 Non-open partner	.27 Incest		.29 Swallowing semen	.27 Small buttocks
.33 Porn video, female-female	.27 Giving pleasure	.25 Disagreeable partner	.27 Being raped		.29 Large penis	.24 Feet
.31 Group sex	.27 Being sexually desired	.18 Introverted partner	.23 8-year-old		.29 Coitus	.23 Small penis

Figure 2. Dendrogram of the cluster analysis of women's sexual preferences. Height is defined such that among all the items grouped together below a given height `h`, every pair has an absolute Kendall correlation of at least 1 - `h`.

For factor analysis, we again count zero cells. Overall, 21% of all pairs of responses choices never occur; 94% of item pairs have at least one of these zeros in their frequency table. The factor analyses are depicted in Table 5 and Table 6. The first factor is driven by interest in women. At level 2, factor 2 looks like a tenderness factor, and also has items concerning interest in men. At level 3, factor 2 loses weight on items for interest in men and gains negative weight for nonconsent items such as incest and rape. The new factor 3 concerns interest in men, particularly semen, but it is positively related to the previous factor 1 (women). At level 4, factor 4 comprises interest in more feminine or less masculine men, such as female-to-male transgender people and men with small penises. It is negatively related to the previous factor 2 (tenderness), but positively with factor 3 (semen). At level 5, factor 5 concerns pornographic tropes such as sex with a stranger or a "bad boy", and also weights items for actually viewing pornography. It is strongly positively correlated with the previous factor 3 (semen). At level 6, factor 6 concerns the anuses, one's own and those of others. The final factor concerns domination and submission, but especially submission. In order, the seven factors could be described as: women, tenderness, semen, feminine men, pornography, the anus, and power.

Table 5. Factor analyses of women's sexual preferences. Shown are the top five items of each factor (columns) in each factor analysis (row groups), scored by factor loading (which is sorted by absolute value).
1 (Women)	2 (Tenderness)	3 (Semen)	4 (Feminine Men)	5 (Pornography)	6 (Anus)	7 (Power)
—
.81 Giving cunnilingus
.78 Woman
.77 Masturbating a woman
.77 Porn video, female-female
.77 Feminine woman
—	—
.78 Giving cunnilingus	.85 Being sexually desired
.76 Porn video, female-female	.74 Man
.74 Group sex	.73 Sex in relationship
.74 Woman	.72 Emotional closeness
.74 Masturbating a woman	.72 Coitus
—	—	—
.94 Woman	.84 Being sexually desired	.70 Receiving semen in mouth
.93 Masturbating a woman	-.78 Incest	.70 Swallowing semen
.91 Feminine woman	.77 Feeling in love	.69 Fellating
.89 Giving cunnilingus	.75 Sex in relationship	.61 Large penis
.83 Large breasts	.75 Emotional closeness	.61 Receiving semen in anus
—	—	—	—
.94 Woman	.79 Emotional closeness	.68 Receiving semen in mouth	.57 Small penis
.92 Masturbating a woman	.79 Sex in relationship	.68 Fellating	.55 Feminine man
.90 Feminine woman	.78 Feeling in love	.67 Swallowing semen	.53 Small feet
.87 Giving cunnilingus	.78 Being sexually desired	.66 Large penis	.50 FtM
.81 Large breasts	.72 Giving pleasure	.63 Being controlled	.48 Large feet
—	—	—	—	—
.94 Woman	.79 Sex in relationship	.89 Receiving semen in mouth	.56 Feminine man	.67 Stranger
.92 Masturbating a woman	.79 Emotional closeness	.88 Swallowing semen	.56 Small penis	.64 Rebel
.90 Feminine woman	.78 Being sexually desired	.60 Fellating	.55 Small feet	.63 Large penis
.86 Giving cunnilingus	.78 Feeling in love	.57 Receiving semen in anus	.49 Large feet	.63 Acquaintance
.81 Large breasts	.73 Giving pleasure	.47 Giving a man anilingus	.48 FtM	.61 Group sex
—	—	—	—	—	—
.94 Woman	.80 Emotional closeness	.85 Receiving semen in mouth	.62 Feminine man	.67 Stranger	.71 Receiving anilingus
.92 Masturbating a woman	.79 Sex in relationship	.85 Swallowing semen	.59 Small penis	.64 Rebel	.68 Giving a woman anilingus
.90 Feminine woman	.78 Being sexually desired	.56 Fellating	.52 FtM	.63 Large penis	.63 Giving a man anilingus
.85 Giving cunnilingus	.78 Feeling in love	.46 Receiving semen in anus	.52 Small feet	.62 Acquaintance	.46 Receiving penis in anus
.81 Large breasts	.73 Giving pleasure	.40 Receiving semen in vagina	.49 Neurotic partner	.62 Group sex	.41 Receiving semen in anus
—	—	—	—	—	—	—
.94 Woman	.81 Sex in relationship	.85 Receiving semen in mouth	.62 Feminine man	.62 Porn video, male-female	.69 Giving a woman anilingus	.70 Being tied up
.92 Masturbating a woman	.80 Emotional closeness	.84 Swallowing semen	.60 Small penis	.61 Large penis	.67 Receiving anilingus	.70 Being controlled
.91 Feminine woman	.79 Being sexually desired	.56 Fellating	.53 FtM	.60 Masculine man	.62 Giving a man anilingus	.61 Receiving pain
.86 Giving cunnilingus	.78 Feeling in love	.45 Receiving semen in anus	.52 Small feet	.59 Stranger	.41 Receiving penis in anus	.58 Being insulted
.82 Large breasts	.74 Giving pleasure	.41 Receiving semen in vagina	.49 Large feet	.57 Acquaintance	.35 Urinating on partner	.56 Tying up

Table 6. Correlation of factor scores for women's sexual preferences, between factors at each level of the bass-ackwards procedure (rows) with those at the previous level (columns). Off-diagonal elements with absolute value of 1/3 or more are in bold.
	1	2	3	4	5	6
	—
1	.99
2	-.38
	—	—
1	.74	-.12
2	-.38	.98
3	.68	.03
	—	—	—
1	.99	-.05	-.03
2	-.07	.98	-.17
3	.12	.06	.93
4	.10	-.67	.40
	—	—	—	—
1	.99	-.09	.04	.08
2	-.06	.99	.01	-.50
3	-.05	-.25	.60	.27
4	.04	-.46	.02	.98
5	.10	.16	.81	-.13
	—	—	—	—	—
1	.99	-.06	.01	.03	.05
2	-.08	.99	-.23	-.46	.15
3	-.00	-.12	.97	.00	-.03
4	.07	-.44	.15	.97	-.05
5	.05	.14	.08	-.07	.99
6	.12	-.32	.31	.44	.01
	—	—	—	—	—	—
1	.99	-.04	-.00	.04	.09	.04
2	-.07	.99	-.13	-.44	.15	-.27
3	.00	-.14	.99	.07	.04	.08
4	.06	-.46	.08	.99	-.07	.25
5	-.00	.27	-.12	-.11	.88	-.10
6	.03	-.22	-.01	.19	-.01	.97
7	.02	-.24	.29	.11	.45	.26

Discussion

Our Internet sample of 459 men and 464 women exhibits a number of ways to group sexual preferences—some familiar, some novel—which vary between genders as well as between the two methods, clustering and factor analysis. A few groups reoccur frequently between methods and genders. Gender preferences—preferences for sex with men or women in particular—figure largely in every case, providing support for the traditional emphasis on gender preferences in the study of sexual preferences. Other reoccurring groups include tenderness (an interest in things such as sex in romantic relationship, giving one's partner sexual pleasure and emotional closeness) and unpersonability (an interest in partners who have conventionally undesirable personality traits, such as low openness and high neuroticism).

In men, both methods show groups for preferences concerning men, women, kink, and unpersonability. The cluster analysis, but not the factor analysis, has a separate group for rape and presumed rape such as sex with an 8-year-old; the factor analysis puts these items at negative loadings in the tenderness factor. Possibly the tenderness factor is more of a social-desirability factor.

In women, both methods show groups for preferences concerning women, tenderness, and men, although the men group that appears in the factor analysis is dominated by feminine traits. The prominence of the tenderness group supports theories that intimacy and romance are particularly important for women (Meana, 2010). Meanwhile, a group for power relations that appears only for factor analysis and only at stage 7 provides weak support for theories that construe sexual interests in terms of power.

Notice that the group for interest in the other sex, separate from same-sex interest, appears more readily in men than women. This suggests that heterosexual and homosexual interest is more independent in men than women, which is reminiscent of findings that lesbians are more likely than gay men to report a different orientation over time (Ott, Corliss, Wypij, Rosario, & Austin, 2011; Mock & Eibach, 2012; Savin-Williams, Joyner, & Rieger, 2012).

There are several limitations inherent in the design of this study. Most obvious is that our results are shaped by the design of the questionnaire; while we attempted to be theoretically neutral, or at least to cover many different theories, there can be no truly neutral questionnaire. There are also the usual honesty and accuracy concerns with self-report, particularly when asking subjects about such sensitive matters as their interest in sex with an 8-year-old. Our use of an anonymous Internet sample, instead of a traditional subject pool, may have made subjects somewhat more willing to be honest. Phallometry could be a useful replacement or addition to self-report in men, but genital arousal does not exhaust the concept of sexual arousal (Toates, 2009), particularly in women (Chivers, Seto, Lalumière, Laan, & Grimbos, 2010), let alone sexual preference. Finally, more detailed measurement of gender identity, along with targeted sampling, would be necessary to examine sexual preferences among transgender people.

A more subtle issue is that sexual preferences may not be stable, especially in their details. As previously mentioned, people's reported orientation may change over the years. Preferences may also be influenced by circumstantial factors such as menstrual-cycle phase (Gildersleeve, Haselton, & Fales, 2014). Ariely, Loewenstein, and Prelec (2006) challenge the very idea of preferences by showing that whether people regard an experience of hearing poetry as work or play—and hence worth paying for or being paid for—can be influenced by prompting them to think of it as one or the other. Finding people's "enduring patterns" of sexual interests may require measuring them repeatedly in a variety of situations.

Appendix

Below is the complete text of the sexual-preference items. Each item is prefixed with its name, which we use in tables and figures but we did not show to subjects. Items marked "[M]" or "[F]" were only shown to male or female subjects, respectively.

[Solo masturbation] [M] Masturbating alone (touching your penis; jacking off)
[Solo masturbation] [F] Masturbating alone (touching your clitoris or vagina)
[Coitus] [M] Having vaginal sex with a woman (penetrating a woman with your penis)
[Coitus] [F] Having vaginal sex with a man (being penetrated by a man's penis)
[Penis in woman's anus] [M] Giving anal sex to a woman (penetrating a woman's anus with your penis; topping)
[Penis in man's anus] [M] Giving anal sex to a man (penetrating a man's anus with your penis; topping)
[Receiving penis in anus] Receiving anal sex (being anally penetrated by a man's penis; bottoming)
[Being fellated] [M] Receiving oral sex (fellatio; getting a blowjob)
[Fellating] Giving a man oral sex (fellatio; giving a blowjob)
[Receiving cunnilingus] [F] Receiving oral sex (cunnilingus; being eaten out)
[Giving cunnilingus] Giving a woman oral sex (cunnilingus; eating her out)
[Giving a woman anilingus] Giving a woman a rimjob (anilingus; licking a woman's anus)
[Giving a man anilingus] Giving a man a rimjob (anilingus; licking a man's anus)
[Receiving anilingus] Receiving a rimjob (anilingus; having your anus licked)
[Being masturbated] [M] Receiving masturbation from a partner (getting a handjob; being jacked off)
[Masturbating a man] Masturbating a man (giving a handjob; jacking him off)
[Being masturbated] [F] Receiving masturbation from a partner (having your clitoris or vagina touched by your partner's hands)
[Masturbating a woman] Masturbating a woman (touching a woman's clitoris or vagina with your hands)
[Being penetrated by object] Being penetrated by an object, such as a dildo
[Penetrating with object] Penetrating your partner with an object, such as a dildo
[Ejaculating into mouth] [M] Ejaculating (cumming) in your sex partner's mouth without a condom
[Ejaculating into vagina] [M] Ejaculating (cumming) in your sex partner's vagina without a condom
[Ejaculating into anus] [M] Ejaculating (cumming) in your sex partner's anus without a condom
[Receiving semen in mouth] Receiving a man's semen/cum in your mouth without a condom
[Receiving semen in vagina] [F] Receiving a man's semen/cum in your vagina without a condom
[Receiving semen in anus] Receiving a man's semen/cum in your anus without a condom
[Swallowing semen] Swallowing a man's semen/cum
[Controlling] Totally controlling your sex partner
[Being controlled] Being totally controlled by your sex partner
[Causing pain] Causing pain to your sex partner
[Receiving pain] Having your sex partner cause you pain
[Tying up] Tying up your sex partner as part of sex (bondage)
[Being tied up] Being tied up by your sex partner as part of sex (bondage)
[Urinating on partner] Urinating on your sex partner as part of sex (watersports)
[Being urinated on] Being urinated on by your sex partner as part of sex (watersports)
[Leather] Using leather as part of sex
[Insulting] Calling your sex partner insulting names during sex (e.g., "slut")
[Being insulted] Being called insulting names during sex (e.g., "slut")
[Feet] Sex inolving your or your partner's feet
[Group sex] Having sex with two or more people at once
[Voyeurism in open] Watching other people naked, masturbating, or having sex, when they know that you're watching
[Voyeurism in secret] Watching other people naked, masturbating, or having sex, when they don't know that you're watching
[Unconscious partner] Sex with someone while they're unconscious (e.g., asleep or passed out from alcohol or a drug)
[Raping] Raping someone
[Being raped] Being raped
[Porn stories] Reading pornographic or erotic stories
[Porn videos or pictures] Viewing pornographic or erotic videos or pictures
[Porn video, male-female] Watching a video of a man and woman having sex
[Porn video, female-female] Watching a video of two women having sex
[Porn video, male-male] Watching a video of two men having sex
[Incest] Sex with someone you're related to (a family member)
[Sex in relationship] Sex with someone you're in a relationship with
[Friend] Sex with a friend you aren't in a relationship with
[Acquaintance] Sex with someone you met a few hours ago
[Stranger] Anonymous sex with a total stranger
[Hugging] Hugging
[Kissing] Kissing
[Emotional closeness] Feeling emotionally close to your sex partner
[Feeling in love] Feeling in love with your partner
[Being sexually desired] Being sexually desired by your partner
[Giving pleasure] Giving your partner sexual pleasure
[Large penis] Sex with a man with a particularly large penis
[Small penis] Sex with a man with a particularly small penis
[Large breasts] Sex with a woman with particularly large breasts
[Small breasts] Sex with a woman with particularly small breasts
[Large buttocks] Sex with someone with particularly large buttocks
[Small buttocks] Sex with someone with particularly small buttocks
[Large feet] Sex with someone with particularly large feet
[Small feet] Sex with someone with particularly small feet
[Man] Sex with a man
[Feminine man] Sex with a very feminine man
[Masculine man] Sex with a very masculine man
[FtM] Sex with a trans-man (i.e., someone assigned female sex by a doctor at birth, but who now identifies as male)
[Woman] Sex with a woman
[Feminine woman] Sex with a very feminine woman
[Masculine woman] Sex with a very masculine woman
[MtF] Sex with a trans-woman (i.e., someone assigned male sex by a doctor at birth, but who now identifies as female)
[8-year-old] Sex with an 8-year-old
[14-year-old] Sex with a 14-year-old
[70-year-old] Sex with a 70-year-old
[Rich partner] Sex with a wealthy person with a prestigious profession
[Rebel] Sex with a rebel or rule-breaker (bad boy, bad girl)
[Experienced partner] Sex with a person with lots of previous sexual experience
[Virgin] Sex with a virgin
[Extraverted partner] Sex with an extraverted, enthusiastic person
[Disagreeable partner] Sex with a critical, quarrelsome person
[Conscientious partner] Sex with a dependable, self-disciplined person
[Neurotic partner] Sex with an anxious, easily upset person
[Open partner] Sex with a person who is complex and open to new experiences
[Introverted partner] Sex with a reserved, quiet person
[Agreeable partner] Sex with a sympathetic, warm person
[Unconscientious partner] Sex with a disorganized, careless person
[Non-neurotic partner] Sex with a calm, emotionally stable person
[Non-open partner] Sex with a conventional, uncreative person

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