Sunday, April 11, 2010

WHY HUMAN DO SEX

Abstract Historically, the reasons people have sex have


been assumed to be few in number and simple in nature–to

reproduce, to experience pleasure, or to relieve sexual

tension. Several theoretical perspectives suggest that motives

for engaging in sexual intercourse may be larger in

number and psychologically complex in nature. Study 1

used a nomination procedure that identified 237 expressed

reasons for having sex, ranging from the mundane (e.g., ‘‘I

wanted to experience physical pleasure’’) to the spiritual

(e.g., ‘‘I wanted to get closer to God’’), from altruistic (e.g.,

‘‘I wanted the person to feel good about himself/herself’’)

to vengeful (e.g., ‘‘I wanted to get back at my partner for

having cheated on me’’). Study 2 asked participants

(N = 1,549) to evaluate the degree to which each of the 237

reasons had led them to have sexual intercourse. Factor

analyses yielded four large factors and 13 subfactors,

producing a hierarchical taxonomy. The Physical reasons

subfactors included Stress Reduction, Pleasure, Physical

Desirability, and Experience Seeking. The Goal Attainment

subfactors included Resources, Social Status, Revenge, and

Utilitarian. The Emotional subfactors included Love and

Commitment and Expression. The three Insecurity subfactors

included Self-Esteem Boost, Duty/Pressure, and Mate

Guarding. Significant gender differences supported several

previously advanced theories. Individual differences in

expressed reasons for having sex were coherently linked

with personality traits and with individual differences in

sexual strategies. Discussion focused on the complexity of

sexual motivation and directions for future research.
 
Abstract Historically, the reasons people have sex have


been assumed to be few in number and simple in nature–to

reproduce, to experience pleasure, or to relieve sexual

tension. Several theoretical perspectives suggest that motives

for engaging in sexual intercourse may be larger in

number and psychologically complex in nature. Study 1

used a nomination procedure that identified 237 expressed

reasons for having sex, ranging from the mundane (e.g., ‘‘I

wanted to experience physical pleasure’’) to the spiritual

(e.g., ‘‘I wanted to get closer to God’’), from altruistic (e.g.,

‘‘I wanted the person to feel good about himself/herself’’)

to vengeful (e.g., ‘‘I wanted to get back at my partner for

having cheated on me’’). Study 2 asked participants

(N = 1,549) to evaluate the degree to which each of the 237

reasons had led them to have sexual intercourse. Factor

analyses yielded four large factors and 13 subfactors,

producing a hierarchical taxonomy. The Physical reasons

subfactors included Stress Reduction, Pleasure, Physical

Desirability, and Experience Seeking. The Goal Attainment

subfactors included Resources, Social Status, Revenge, and

Utilitarian. The Emotional subfactors included Love and

Commitment and Expression. The three Insecurity subfactors

included Self-Esteem Boost, Duty/Pressure, and Mate

Guarding. Significant gender differences supported several

previously advanced theories. Individual differences in

expressed reasons for having sex were coherently linked

with personality traits and with individual differences in

sexual strategies. Discussion focused on the complexity of

sexual motivation and directions for future research.

Keywords Sexual motivation Sexual intercourse

Gender differences

Introduction

Why people have sex is an extremely important, but

surprisingly little studied topic. One reason for its relative

neglect is that scientists might simply assume that the

answers are obvious: to experience sexual pleasure, to

relieve sexual tension, or to reproduce. Previous research

already tells us that the answers cannot be as few or

psychologically simple. Leigh (1989), for example, documented

seven reasons for sex: pure pleasure, to express

emotional closeness, to reproduce, because a partner wants

it, to please a partner, to make a conquest, and to relieve

sexual tension. The most comprehensive existing taxonomy,

framed from a theoretical perspective of dispositional sexual

motives, documented eight reasons: to feel valued by a

partner, expressing value for a partner, obtaining relief from

stress, nurturing one’s partner, enhancing feelings of personal

power, experiencing a partner’s power, experiencing

pleasure, and procreating (Hill & Preston, 1996).

Several theoretical perspectives suggest that reasons for

engaging in sexual intercourse might be even more

numerous and complex than even this previous research

suggests. With the exception of ‘‘to make a conquest,’’ most

of the documented reasons for having sex above implicitly

assume the context of an ongoing romantic relationship or

long-term mateship. Sexual strategies theory (Buss &

Schmitt, 1993) and strategic pluralism theory (Gangestad &

Simpson, 2000), however, propose that humans have a

menu of mating strategies, including long-term, short-term,

and extra-pair mating. Thus, there might be reasons for

having sex with a casual sex partner or extra-pair partner,
such as the desire to experience sexual variety (Symons,


1979) or seeking to improve one’s sexual skills (Greiling &

Buss, 2000) that differ from those that motivate sex in the

context of an ongoing romantic relationship.

Even within the context of an ongoing mateship, there

could be numerous reasons for having sex beyond those

already documented. For example, sex might be used to

reward a partner or as a favor in exchange for something the

partner has done. Or sex might be used to punish a partner,

such as when someone engages in a retaliatory affair in

order to exact revenge on a partner for having committed

some violation within the relationship (Greiling & Buss,

2000). Also, within an ongoing relationship, sex might be

used to intensify the relationship, escalate the level of

commitment within the relationship, or turn a short-term

relationship into a long-term relationship (Buss, 2003). In

the clinical literature, Basson (2000) described how women

may engage in sexual intercourse for the ‘‘spin-offs’’ they

receive, such as emotional closeness, bonding, commitment,

love, affection, acceptance, tolerance, and closeness.

From yet another perspective, people might use sex as a

form of ‘‘mate guarding’’ (Buss & Shackelford, 1997). This

could function in one of several possible ways. First, satisfying

a partner sexually might function to deter the partner

from seeking sexual gratification elsewhere. Second, this

strategic use of sexuality might send signals to potential

mate poachers, perhaps by rendering the partner less ‘‘open’’

to extra-pair liaisons, causing potential mate poachers to

choose other potential targets (Schmitt, 2004; Schmitt &

Buss, 2001).

Another perspective comes from the literature on sperm

competition (Baker & Bellis, 1995; Shackelford, Pound,

Goetz, & LaMunyon, 2005). From this perspective, a man

whose partner might have been sexually unfaithful might

seek sex, which functions to displace the sperm of the rival

male. Or a woman might deplete the sperm of her partner,

leaving few available for insemination of rival women.

None of these hypothesized functions, of course, need

operate through conscious psychological mechanisms.

More generally, sex can be viewed as a fungible resource–

something that one person has the potential to give

and something that another person may want. As a soughtafter

resource, sex can be exchanged for other resources.

Exchanging sex for money, as in the case of prostitution, is

one obvious example (Burley & Symanski, 1981). Sex

could also be exchanged for meat, as occurs among many

traditional hunter-gatherer groups such as the Ache of

Paraguay (Hill & Hurtado, 1996). Sex could be exchanged

for favors, special privileges, a preferred job, or indeed for

any resource.

Finally, the psychology of sex does not occur merely

between the individual partners directly involved. Sex

occurs within a broader social and cultural context, with

implications for prestige, status, and reputation (Buss,

2003). Having sex with a high status individual, for

example, might raise a person’s status within the group.

Within some groups, having sex with numerous partners

might enhance a person’s reputation, providing the motivational

impetus for initiating sex. Sex, of course, can

sometimes damage a person’s status and reputation, providing

reasons for avoiding it or concealing it from others

in the group. In sum, because sex has consequences for

status and reputation that can act as incentives (or deterrents),

a person might be motivated to have sex for social

reasons that have nothing to do with the personal relationship

within which it occurs. All of these diverse theoretical

perspectives, when taken together, point to a

singular conclusion: The reasons people have sex are likely

to be far more numerous and psychologically complex than

previous taxonomists have envisioned.

The current research had several primary goals: (1) to

identify a broader array of potential reasons that motivate

people to engage in sexual intercourse using a nomination

procedure designed to survey the wider domain of

reasons; (2) to develop an organized taxonomy of reasons

for sex using a large sample of women and men; (3) to

provide a more comprehensive research tool that can be

used by sex researchers; (4) to identify whether women

and men differ in their expressed reasons for engaging in

sexual intercourse; and (5) to examine whether individual

differences in sexual strategies, as measured by the

Sociosexuality Inventory (Simpson & Gangestad, 1991),

are linked to individual differences in reasons for having

sex.

Regarding gender differences, previous researchers have

explored this issue in a delimited way. Some have found

that men are more motivated by purely physical reasons,

such as physical release or simply because they are ‘‘horny,’’

whereas women are more motivated by emotional

reasons, such as to become psychologically closer to a

partner (e.g., Carroll, Volk, & Hyde, 1985; Denney, Field,

& Quadagno, 1984; Leigh, 1989). Others have found that

men, more than women, have sex in order to provide relief

from stress and to enhance their feelings of personal power

(Hill & Preston, 1996). Several evolution-based theories

suggest that men will be more motivated by the desire for

sexual variety (Symons, 1979), the chance for an opportunistic

copulation (Buss, 2003), the physical appearance

of a potential partner (Buss & Schmitt, 1993), and that

emotional factors, such as expressing love or intensifying

psychological commitment, would figure more prominently

in women’s reasons for having sex (Buss, 2003).

The current research was capable of testing these theories,

as well as providing a more comprehensive atheoretical

description of a potential panoply of gender differences in

the reasons expressed for having sex.

Study 1: Initial Item Generation
Method


Participants were 203 men and 241 women ranging in age

from 17 years to 52 years who were recruited from upper

and lower level psychology classes, graduate classes in

psychology, and from community volunteers who were

participating in several other ongoing studies in the Sexual

Psychophysiology Laboratory at the University of Texas.

Potential volunteers were told the purpose of the study was

to make a comprehensive list of all the reasons why people

engage in sexual intercourse.

Persons who agreed to participate in the study were

asked the following open-ended prompt, ‘‘Please list all the

reasons you can think of why you, or someone you have

known, has engaged in sexual intercourse in the past.’’

Participants were encouraged to list as many responses as

possible. Efforts were made to ensure confidentiality by

having participants sit at a distance from other participants

such that other’s responses could not be easily read. Anonymity

was assured by having participants include only

their age and gender on their answer sheets.

Results

A total of 715 reasons were collected. The authors each

independently reviewed the reasons and noted those that

were either identical or similar with minor wording changes.

Reasons given that both authors marked as similar

were deleted or compiled into one combined response,

resulting in 237 distinct reasons. The 237 reasons (see

Table 3) obtained were listed using a conventional questionnaire

format with each item presented as a brief

descriptive statement to which subsequent participants

rated the likelihood that a given reason has or would lead

them to engage in sexual intercourse. The questionnaire

was termed the Why Have Sex? (YSEX?) questionnaire.

The following instructional set was given at the beginning

of the instrument, ‘‘People have sex (i.e., sexual intercourse)

for many different reasons. Below is a list of some

of these reasons. Please indicate how frequently each of

the following reasons led you to have sex in the past. For

example, if about half of the time you engaged in sexual

intercourse you did so because you were bored, then you

would circle ‘‘3’’ beside question 3. If you have not had sex

in the past, use the following scale to indicate what the

likelihood that each of the following reasons would lead

you to have sex. I have had sex in the past because...’’ The

response choices were listed on a 5-point Likert scale, with

scale interval anchors being None of my sexual experiences

(1), A few of my sexual experiences (2), Some of my sexual

experiences (3), Many of my sexual experiences (4), and All

of my sexual experiences (5).

Study 2: Psychometric Analyses

Method

Participants

A total of 1,549 undergraduate students (503 men, 1046

women) participated in this study in exchange for course

credit. Participants were distinct from those who took part

in Study 1. Participants were enrolled in either the 2000–

2003 Fall sessions of Introductory Psychology courses

(September–December) or the 2001–2004 Spring Introductory

Psychology sessions (January–May). Sample sizes

varied between cohorts (2000–2001, n = 570; 2001–2002,

n = 341; 2002–2003, n = 341; 2003–2004, n = 297). Participants

ranged in age from 16 years to 42 years (96%

between the ages of 18 and 22), and the mean age was

19 years.

The sample consisted of 62% Caucasian, 4% African

American, 15%Hispanic,15% Asian American,<1% Native

American, and 3% ‘‘other ethnicity’’ participants. Ethnicity

was determined with the question, ‘‘What ethnicity do you

most identify with?’’ Region of heritage was also assessed

based on countries of birth or countries of parents’ birth.

Across ethnicities, most participants reported North American

heritage (96% of Caucasians, 91% of African Americans,

94% of Hispanics, 71% of Asian Americans, 67% of

Native Americans, and 59% of ‘‘other’’ ethnicities). The

second most substantial reported heritage was Asian heritage

(23% of Asian Americans and 33% of ‘‘other’’ ethnicities).

Less than 5% of each ethnicity reported South American,

African, Middle Eastern, Western European, Eastern European,

or South Pacific heritage. Religious affiliations varied,

with 36% Fundamentalists, 25% Catholics, 14% Protestants,

14% Atheists/Agnostics, 5% Jewish, 4% Hindus, 2% Buddhists,

1% Muslims, and <1% Pagans/Spiritualists.

Sexual experience data were available for 910 women

and 343 men. Of these, 73% of women and 68% of men

reported having experienced sexual intercourse in the past.

Among both men and women, 88% reported having engaged

in oral sex and 95% reported having engaging in

some form of sexual petting in the past. Four percent of

the women and 2% of men were married. Six percent of

women and 5% of men were living with a sexual partner.
Measures


Reasons for sexual intercourse Motivators for engaging

in sexual intercourse were measured using the 237 item

YSEX? questionnaire that was developed in Study 1.

Personality The Big Five Inventory-short form (BFI) is

a 44 item inventory developed by John, Donahue, and

Kentle (1991) to assess each of the ‘‘Big Five’’ personality

dimensions: Neuroticism, Extraversion, Openness to

Experience, Agreeableness, and Conscientiousness. The 44

self-descriptive statements were measured on a 5-point

scale, with responses ranging from disagree strongly (1) to

agree strongly (5).

Sexual strategies The following five items from the

Sociosexual Orientation Inventory (SOI; Simpson &

Gangestad, 1991) were used to analyze unrestricted sexual

behavior and fantasy: ‘‘With how many partners have you

had sex (intercourse or oral sex) in the past year?’’; ‘‘With

how many partners will you probably have sex with

(intercourse or oral sex) over the next five years?’’; ‘‘With

how many partners have you had sexual intercourse, or oral

sex, on one and only one occasion?’’; ‘‘When in a stable

and committed relationship, how often would you fantasize

about sex with someone other than your current partner?’’;

and ‘‘Sex without love is okay.’’ An SOI composite was

computed by averaging the sum of the five z-transformed

scores.

Procedure

Participants were administered a demographics questionnaire,

the YSEX? questionnaire derived from Study 1, the

short form version of the Big Five Inventory (John et al.,

1991), selected items from the Sociosexual Orientation

Inventory (Simpson & Gangestad, 1991), and a number of

additional sexually relevant questionnaires not reported

here. In each cohort, participants were administered questionnaires

in small groups of 5–10 same-sex individuals.

To preserve privacy, participants were given either partitions

or several feet of space from other participants. Participants

were informed of the sexual nature of the study

before they applied to participate. Same-sex researchers

informed participants of the sexual material, obtained

consent, administered questionnaire packets, and answered

participant questions that arose during testing. Confidentiality

was protected by assigning each participant with a

randomized code number connected to all of his or her

data, and consent forms were kept in a separate file. Upon

completion, questionnaire packets were inserted into a large ‘‘drop box’’ as participants exited the testing room.


Questionnaire data were stored in locked file cabinets, and

all files connected to the study were password-protected.

The Institutional Review Board at the University of Texas

at Austin approved this research from 2000 to 2004.

Results

Item analyses

Most and least frequently endorsed reasons for having

sex There were nine themes that appeared to characterize

the most frequently endorsed reasons for having intercourse:

(1) pure attraction to the other person in general;

(2) experiencing physical pleasure; (3) expression of love;

(4) having sex because of feeling desired by the other; (5)

having sex to escalate the depth of the relationship; (6)

curiosity or seeking new experiences; (7) marking a special

occasion for celebration; (8) mere opportunity; and (9) sex

just happening due to seemingly uncontrollable circumstances.

Table 1 shows the 50 reasons for having sex receiving

the highest endorsements for men and women separately.

The most frequently endorsed reason why both men and

women reported engaging in sexual intercourse was because

they were attracted to the person. As can be seen in

Table 1, out of a pool of 237 items, 8 of the top 10, and 20

of the top 25 reasons given for engaging in sexual intercourse

were similar for men and women.

Table 2 presents the 50 most infrequently endorsed

reasons for having sexual intercourse out of the possible

237 reasons. The least frequently endorsed reasons for

having intercourse could be categorized into five broad

themes. One theme involved wanting to harm another

person, either a partner (e.g., ‘‘I was mad at my partner, so I

had sex with someone else’’), a rival (e.g., ‘‘I wanted to

hurt an enemy’’) or a stranger (e.g., ‘‘I wanted to give

someone else a sexually transmitted disease (e.g., herpes,

AIDS)’’. A second theme involved attaining resources such

as a job, a promotion, money, drugs, or gifts. A third

common theme revolved around enhancing social status

(e.g., ‘‘I wanted to be popular’’; ‘‘I wanted to have more sex

than my friends’’). A fourth theme centered on having sex

as a means to a seemingly unrelated end, such as getting rid

of a headache or menstrual cramps, and a fifth theme

involved having sex out of duty or pressure.

Gender differences in reasons for having sex To examine

gender differences at the item level, given that 237 t-tests

would be conducted, we set the significance threshold at a

conservative level of p < .005. Thus, roughly one difference

that showed significance at this level would be