Sexual Selection and Human Attraction

Understanding why humans are attracted to particular partners is a central question in the psychology of relationships. Evolutionary psychologists argue that mate preferences are not random — they are shaped by millions of years of natural and sexual selection. This lesson examines Darwin's theory of sexual selection, evolutionary explanations of partner preferences, the role of physical attractiveness, and the importance of self-disclosure in relationship formation.

Key Definition: Sexual selection is a form of natural selection in which individuals with certain traits are more likely to obtain mates and reproduce, passing those traits to offspring. It operates through intrasexual competition and intersexual selection.

Darwin's Sexual Selection

Charles Darwin (1871) proposed that some traits evolve not because they aid survival, but because they aid reproductive success. He identified two mechanisms:

Intrasexual Selection

This refers to competition within one sex (usually males) for access to members of the other sex. Males may compete through physical contests, displays of dominance, or resource holding. The winners of such contests gain mating opportunities.

In humans, intrasexual competition may explain why men tend to be taller and more physically aggressive than women on average.
Buss (1988) found that men are more likely to derogate rivals by questioning their earning potential, while women derogate rivals by questioning their physical attractiveness.

Intersexual Selection

This refers to mate choice by one sex (usually females), whereby individuals prefer partners who display desirable traits. The choosy sex selects partners whose characteristics signal genetic fitness or the ability to provide resources.

Females in many species invest more in offspring (pregnancy, lactation), so they are choosier — this is the basis of Trivers' (1972) parental investment theory.
In humans, intersexual selection may explain female preferences for indicators of resource-holding potential (ambition, wealth, status).

Exam Tip: Make sure you can clearly distinguish between intrasexual and intersexual selection. A common error is to confuse them. Remember: intra = within the same sex (competition); inter = between the sexes (choice).

Evolutionary Explanations of Partner Preferences

Buss's Cross-Cultural Study (1989)

David Buss conducted one of the largest cross-cultural studies in psychology, surveying over 10,000 participants from 37 cultures across 33 countries. He asked participants to rate the importance of various characteristics in a potential mate.

Key Findings:

Preference	Males	Females
Physical attractiveness	Rated as highly important	Rated as less important (compared to males)
Youth	Preferred younger partners (fertility cues)	Less emphasis on youth
Financial resources	Rated as less important	Rated as highly important
Ambition/industriousness	Rated as less important	Rated as highly important
Chastity	Valued more in some cultures	Valued less than by males

Buss argued these preferences are universal and reflect evolved psychological mechanisms:

Male preference for youth and attractiveness → signals fertility and reproductive value.
Female preference for resources and ambition → signals the ability to invest in offspring.

Evaluation of Buss (1989)

Strengths (AO3):

Extremely large, cross-cultural sample — findings replicated across 37 cultures, supporting the idea that preferences are evolved and universal, not merely cultural.
The study has been widely replicated and the core findings hold consistently (Shackelford et al., 2005).

Limitations (AO3):

Gender bias (beta bias): The study may exaggerate gender differences and downplay within-sex variation. Many women also value physical attractiveness, and many men also value resources.
Social desirability: Participants may report socially acceptable preferences rather than what they truly desire.
Culturally biased methodology: The use of questionnaires reflects Western research methods and may not capture partner preferences in non-literate societies.
Socially sensitive: Findings could be used to justify gender stereotypes or inequality.

Key Definition: Parental investment (Trivers, 1972) refers to any investment by a parent in an individual offspring that increases the offspring's chance of survival at the cost of the parent's ability to invest in other offspring. Females typically invest more, leading to greater choosiness.

Physical Attractiveness

The Halo Effect

Dion, Berscheid & Walster (1972) demonstrated the "what is beautiful is good" stereotype — physically attractive people are perceived as possessing other desirable qualities such as intelligence, kindness, and social competence.

Participants were shown photographs of people varying in attractiveness and asked to rate them on personality traits.
Attractive individuals were rated as happier, more successful, and more socially skilled.
This shows that physical attractiveness creates a halo effect — a cognitive bias where one positive trait (attractiveness) influences judgements of unrelated traits.

The Matching Hypothesis

Walster et al. (1966) proposed the matching hypothesis: people seek romantic partners who are similar to themselves in terms of physical attractiveness, rather than simply seeking the most attractive partner.

The Computer Dance Study (Walster et al., 1966):

752 students at the University of Minnesota were randomly paired for a dance.
Physical attractiveness was independently rated by judges.
Contrary to the matching hypothesis, the most attractive partners were preferred regardless of the participant's own attractiveness — i.e., everyone preferred the most attractive dates.

Revised study (Walster & Walster, 1969):

When participants were allowed to choose their own partners (rather than being randomly assigned), there was stronger support for matching — people tended to choose partners of similar attractiveness to themselves.

Evaluation of Physical Attractiveness Research

Strengths:

The halo effect has been replicated many times and has practical applications (e.g., understanding bias in job interviews, legal judgements).
The matching hypothesis has some support from real-world relationship data — couples tend to be of similar attractiveness (Feingold, 1988).
The concept of physical attractiveness can be integrated with evolutionary theory — attractiveness cues (facial symmetry, waist-to-hip ratio) may signal genetic health and fertility (Singh, 1993).

Limitations:

Much research focuses on initial attraction rather than long-term relationships. Partners may become more or less attractive to each other over time as emotional bonds develop.
Physical attractiveness is culturally variable — what is considered attractive differs across time periods and cultures. For example, historical preferences for body shape have changed dramatically.
Research is often conducted on Western, student samples (WEIRD populations), limiting generalisability.
The matching hypothesis assumes attractiveness can be objectively rated. In reality, perceptions of attractiveness are subjective and influenced by personal experience, mood, and context.

Self-Disclosure

Jourard's Research

Sidney Jourard (1971) argued that self-disclosure — the revealing of personal information about oneself to another person — is crucial for relationship development. He proposed that reciprocal self-disclosure builds trust and intimacy.

Jourard found that disclosure is often reciprocal: when one person reveals personal information, the other tends to respond in kind.
Disclosure must be appropriate to the stage of the relationship — too much disclosure too early can be off-putting.

Social Penetration Theory (Altman & Taylor, 1973)

Altman and Taylor proposed that relationships develop through gradual increases in self-disclosure. They used the metaphor of an onion — personality has multiple layers, and disclosure involves "peeling back" these layers over time.

Two dimensions of disclosure:

Breadth — the range of topics discussed. Early in a relationship, people discuss many topics but at a superficial level.
Depth — how personal or intimate the information is. As a relationship develops, disclosure becomes deeper and more personal.

Early stages involve low-risk, superficial information (hobbies, opinions). As trust builds, partners share more intimate information (fears, past experiences, feelings). Relationships stall or dissolve if disclosure does not deepen appropriately.

Evaluation of Self-Disclosure Research

Strengths:

Supported by research: Sprecher et al. (2013) found that reciprocal self-disclosure increased liking between strangers in a laboratory setting.
The theory has practical applications — it is used in couples therapy to help partners improve communication.

Limitations:

Cultural variations: self-disclosure norms differ across cultures. In collectivist cultures, self-disclosure may be less valued or expressed differently.
Gender differences: women tend to disclose more than men in Western cultures (Dindia & Allen, 1992), suggesting the theory may not apply equally to both sexes.
The onion metaphor is overly simplistic — disclosure does not always follow a neat, linear pattern. People may reveal deep information early or withhold it throughout a relationship.

Exam Tip: When discussing self-disclosure, always link it to relationship formation specifically. AQA examiners want to see that you understand how disclosure operates in the early stages of relationships, not just in established partnerships.

Summary

Topic	Key Theorist(s)	Key Concept
Sexual selection	Darwin (1871)	Intrasexual competition; intersexual choice
Partner preferences	Buss (1989)	Cross-cultural: males value youth/attractiveness, females value resources
Halo effect	Dion et al. (1972)	"What is beautiful is good" stereotype
Matching hypothesis	Walster et al. (1966)	Partners tend to be of similar attractiveness
Self-disclosure	Jourard (1971); Altman & Taylor (1973)	Reciprocal disclosure builds intimacy; onion model

Exam Tip: For 16-mark essays on factors affecting attraction, structure your answer using two or three factors (e.g., physical attractiveness + self-disclosure + filter theory) with AO1 description, AO3 evaluation, and a conclusion that weighs their relative importance.