月经周期对女性知觉性侵犯遭遇的影响_英文_

心 理 学 报 2007，39（3）：536~540 Acta Psychologica Sinica

Women’s Perceptions of Men’s Sexual Coerciveness

Change Across the Menstrual Cycle

Christine E. Garver-Apgar1, Steven W. Gangestad1, and Jeffry A. Simpson2

1

University of New Mexico 2Texas A&M University

Ancestral women would have suffered higher costs if they were raped or sexually coerced during the fertile phase of their reproductive cycle. Accordingly, selection pressures should have made women more sensitive to cues of male sexual coerciveness near ovulation. Normally ovulating women watched videotaped interviews of men trying to attract another woman and then rated each man’s probable sexual coerciveness. Women nearing ovulation rated men as more coercive relative to women in the non-fertile phase. Moreover, fertile women’s judgments of men’s coerciveness were better predicted by an aggregate of women’s responses than were judgments of non-fertile women, suggesting that women are more attuned to salient cues of potential coerciveness during the fertile phase of the cycle, and thus, may be less error-prone. Because these findings are unlikely to be explained by general-purpose learning mechanisms, they suggest that women may possess specially designed perceptual counter-strategies that guard against male sexual coercion. Keywords: sexual coerciveness, ovulation, non-fertile phase.

月经周期对女性知觉性侵犯遭遇的影响

女性在排卵期遭遇强奸或其它形式的性侵犯可能会受到较大伤害。进化历史中女性遭遇性侵犯的危险不断重现使现代社会女性在排卵期对男性性侵犯的线索较为敏感。本研究旨在探讨女性被试观看男性试图吸引其它女性的录像后如何评价每位男性性侵犯的可能性。研究发现接近排卵期的女性比不处于排卵期的女性更可能认为男性会进行性侵犯。这些发现显示，女性具有特定的知觉进化机制来警惕性侵犯，这种特定的进化机制可能受到月经变化的调节。 关键词：性侵犯，排卵期，非生育期。 分类号：B84-069

The evolutionary perspective suggests that some adaptive biases that avert costly errors (e.g., Haselton psychological processes should have been shaped by & Buss, 2000; Haselton, Nettle, & Andrews, 2005; natural selection because they benefited ancestral Haselton & Nettle, 2006), social categorization (e.g., individuals in very specific ways. One goal of Kurzban, Cosmides, & Tooby, 2001; Cosmides, evolutionary psychology is to identify these Tooby, & Kurzban, 2003), prejudice and stereotyping features—psychological adaptations—within the (e.g., Schaller, Conway, & Tanchuk, 2002; Park, larger network of psychological processes (including Faulkner, & Schaller, 2003), and trait inferences byproducts, features not directly shaped to perform based on specific facial features (e.g., Zebrowitz, Hall, specific functions). Documenting adaptation is a Murphy, & Rhodes, 2002). Ingenious methods have difficult and “onerous” process (Williams, 1966), one been developed to demonstrate the design properties that involves showing that a feature exhibits “special of these social judgment adaptations.

To demonstrate the existence of an adaptation, one design” for performing a specific function not

must show that a feature’s fit with and “solution” to explainable by an account other than selection for that

an evolutionary-relevant problem would not likely function (Andrews, Gangestad, & Matthews, 2002;

have been shaped ontogenetically through general-Thornhill, 1990, 1997).

purpose learning processes (see Andrews et al., 2002). Evolutionary scientists have begun to document the

One strategy is to link psychological features with specific design features of various social judgments

underlying physiological processes that are unlikely and perceptions, including social contract algorithms

to be shaped or controlled by general-learning (e.g., Fiddick, Cosmides, & Tooby, 2000; Cosmides

processes. For example, when women are fertile (on & Tooby, 1992; but see Sperber & Girotto, 2002),

days just prior to ovulation), they are more attracted

to the scent of symmetrical men (i.e., men more likely Received 2006-12-30

to possess “good genes”; Gangestad & Thornhill, Correspondence should be addressed to Christine Garver-Apgar,

1998; Rikowski & Grammer, 1999; Thornhill & Department of Psychology, University of New Mexico, Logan Hall,

Gangestad, 1999; Thornhill, Gangestad, Miller, Albuquerque, NM 87131, USA, ; e-mail: [email protected].

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3期 Christine E. Garver-Apgar, et al. Women’s Perceptions of Men’s Sexual Coerciveness Change Across the Menstrual Cycle 537

Scheyd, McCollough, & Franklin, 2003), to the scent of dominant men (Havlicek, Roberts, & Flegr, 2005), to men who display greater social presence and intrasexual competitiveness (Gangestad, Simpson, Cousins, Garver-Apgar, & Christensen, 2004), to men with deep (more masculine) voices (Feinberg, Jones, Law-Smith, Moore, DeBruine, Cornwell, Hiller, & Perrett, 2006; Puts, 2005), and to masculine faces (Johnston, Hagel, Franklin, Fink, & Grammer, 2001; Penton-Voak & Perrett, 2000; Penton-Voak, Perrett, Castles, Burt, Koyabashi, & Murray, 1999). Women in the fertile phase also report greater sexual attraction to men other than their primary partners (Gangestad, Thornhill, & Garver, 2002; Gangestad, Thornhill, & Garver-Apgar, 2005). All of these effects are derived from the hypothesis that selection shaped women to seek potential genetic benefits through mating more so when fertile than when non-fertile (Gangestad & Thornhill, 1998, 2003; see also review in this issue, Garver-Apgar, Gangestad, & Thornhill, 2006). Because these patterned, context-specific shifts do not appear to be explained by general-purpose learning processes, they may be specially-designed female adaptations for mate choice.

To our knowledge, no research has documented adaptive changes in particular social judgment processes across the female menstrual cycle. The current study was designed to examine women’s perceptions of men’s sexual coerciveness across the cycle. From an evolutionary perspective, women should be sensitive to cues of male sexual coerciveness and typically avoid men who are perceived to be sexually coercive (Thornhill & Palmer, 2000) *. Ancestrally, however, women would have suffered more negative consequences if they were sexually victimized when fertile, given the increased risk of conceiving the offspring of a non-investing and potentially low fitness male. (See Chavanne & Gallup, 1998; Petralia & Gallup, 2002; and Bröder and Hohmann, 2003, for demonstrations of counter-strategies based on this reasoning.) Selection, therefore, may have shaped women’s perception of men’s sexual coerciveness to vary across the reproductive cycle in two distinct ways. First, when near ovulation, women might err on the side of caution when assessing men’s potential sexual coerciveness. According to Error Management Theory (Haselton & Buss, 2000), when the costs of being sexually victimized are highest, women should shift their perceptions to decrease false negative errors at the expense of making more false positive errors. Thus, we predicted that women perceive men as more sexually coercive at fertile points of their cycle than at non-fertile points.

* If one assumes rape was a costly event for ancestral women, one would expect selection to have endowed women with counter-strategies to rape regardless of whether men possess rape-specific adaptations.

Second, when women are fertile, they should be more accurate at detecting men who might use sexually coercive tactics. This hypothesis is very difficult to test directly because accurate information about men’s past coercive behavior is difficult to obtain and, even if available, could be a fallible indicator of men’s general coercive tendencies. Thus, indirect methods must be used to assess women’s accuracy at detecting sexually coercive men. In the present study, we assumed that: (1) women use at least some valid cues associated with potential male sexual coerciveness when judging a particular man’s likelihood of being coercive; (2) the coercive judgments made by each woman contains some perceiver-specific error; and, therefore, (3) the average women’s judgment of a particular man’s coerciveness is more accurate than the ratings of a particular man made by most individual women. Hence, we predicted that the average women’s rating of men’s sexual coerciveness (i.e., the ratings averaged across the full sample of women) predict women’s individual ratings of these men’s sexual coerciveness better for fertile women than for non-fertile women.

Method

Women from the University of New Mexico viewed videotaped interviews of men being interviewed for a possible date and rated each man’s likely sexual coerciveness, given his verbal and nonverbal behavior during the interview. Specifically, 76 men were recruited from introductory psychology classes at Texas A&M University to participate in a study on “Relationship Formation.” Each man was interviewed over a video-camera system by one of two attractive female undergraduates for a potential lunch date. Men first answered general questions posed by the female interviewer, after which another man (actually an experimental accomplice) described as a “competitor for the lunch date” appeared on each participant’s monitor. Each man was then instructed to tell the “competitor” why the female interviewer should choose him for the date over the competitor. Unbeknownst to participants, the interviewer’s questions had actually been scripted and pre-recorded on videotape. Following the interview, each participant was debriefed and permission to use his videotaped interview for future research was obtained (see Simpson, Gangestad, Christensen, and Leck [1999] for details).

Normally ovulating women (those not using any form of hormonal contraception and pre-menopausal; N = 169) were recruited from introductory classes at the University of New Mexico to participate in a study on “Videotape Rating of Men’s Attractiveness” (mean age = 19.56; SD = 1.98). Women viewed one-minute segments of the videotaped interviews. They

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saw either the first segment of the tape when the men responded to the question, “Please tell me about yourself, including who you are, what you like to do, and what you don’t like to do” (N = 50 women), or the last segment when the men told the “competitor” why the interviewer should select them (N = 119 women). Each woman viewed approximately half of the interviews: either the first 40 men (N = 77 women) or the last 36 men (N = 92 women).

Women rated each man on several characteristics, six of which are pertinent to the present study. Three items measured perceptions of male sexual coercion: (1) how sexually coercive (“likely to argue, protest, make verbal or physical threats, or use physical force in order to have sex with women”) each man was; (2) how frightening each man was to them; and (3) how “creepy ” each man appeared to be. Three additional items assessed global perceived traits of each man, each of which is important in relationship evaluations (Simpson & Gangestad, 1992): (4) how kind each man was likely to be; (5) how committed each man was; and (6) how faithful each man was likely to be. All ratings were made on 5-point scales, where 1 = lowest 5%, 2 = lower 30%, 3 = middle 30%, 4 = upper 30%, 5 = highest 5%. Participants were told that the percentages referred to the general population of same-aged men. Correlations between the mean ratings on the three items that assessed coercion across men were: sexually coercive and “creepy,” r = .482; sexually coercive and frightening, r = .858; frightening and “creepy,” r = .714. As expected, these items loaded on a single factor.

Two aggregate variables were created. First, each woman’s responses to the three coerciveness items (Sexual Coerciveness, Frightening, and “Creepy”) were summed to form an overall sexual coerciveness rating for each man she viewed. Second, the average women’s sexual coerciveness rating was computed for each man. Four different sets of averages were calculated, averaging the responses made by women who saw the same segment and the same set of men. For each woman, the average rating was calculated without her individual rating included in the composite.

Women also reported the first day of their last menstrual period and their typical cycle length in order to estimate fertility (i.e., conception probability). We took women’s typical menstrual cycle length (sample mean = 28.90 days; SD = 3.3 days) into account and put each woman on a 29-day cycle before estimating her current day of the cycle (recognizing that ovulation occurs approximately 15 days prior to the end of the cycle [Baker & Bellis, 1995]). We then used actuarial tables based on medical data reported by Jöchle (1973) to estimate the fertility status (conception risk) of each woman.

Results

Multilevel Regressions

Given the multilevel nature of the data (i.e., women’s responses to particular men nested within individual women), the data were analyzed using multilevel regression (SAS 8.0 PROC MIXED). Using maximum likelihood estimation, SAS estimated for each female participant the slope and y intercept of the relation between the average sexual coerciveness rating given to particular men by all women in the sample (a Level-1 predictor) and each female participant’s own sexual coerciveness ratings of those men (a dependent variable). SAS then estimated relations between those slopes and intercepts and two other female characteristics (Level-2 predictors): their fertility status and age. Because the average sexual coerciveness ratings were centered on 0, the y intercepts reflect mean differences in the ratings across women. Thus, associations between fertility status and age with intercept values (i.e., the main effects of conception risk and age) are their associations with the mean ratings.

In all analyses, set (the first 40 men or last 36) and segment (first or last) were included as Level-2 predictors to account for variance associated with viewing one set of men or one segment versus another. Because set and segment effects carry no theoretical importance (i.e., simply by chance even given random assignment of the two sets of men, one might expect women to respond differently to the two sets of men or the two segments of tape), they are not reported. No age effects were found.

Prediction 1

According to Prediction 1, fertile women should, on average, judge men as more sexually coercive than should non-fertile women. The analyses yielded this effect , t (142) = 2.28, p = .024.

We ran comparable analyses replacing women’s coerciveness ratings with the three other male traits/characteristics. As expected, no significant main effects emerged for kindness, t (144) = .64, p = .522, ns ; faithfulness, t (144) = -1.00, p = .321, ns ; or commitment, t (144) = -.96, p = .341, ns . These results provide no evidence that the effect for sexual coerciveness is due to a general tendency for fertile women to systematically perceive higher levels of other types of traits in men when they are in the fertile versus the non-fertile phase of their cycle.

Prediction 2

According to Prediction 2, average women’s ratings of male sexual coerciveness (irrespective of menstrual cycle status) should forecast fertile women’s ratings of sexual coerciveness better than non-fertile women’s ratings. This predicted effect corresponds to an interaction between conception risk

3期 Christine E. Garver-Apgar, et al. Women’s Perceptions of Men’s Sexual Coerciveness Change Across the Menstrual Cycle 539

and the ratings of men averaged across all women. As predicted, this interaction emerged, t (5302) = 2.08, p = .038.*

Also as anticipated, conception risk did not interact with the average women’s ratings of kindness, t (5338) = -.01, p = .992, ns ; faithfulness, t (5340) = -.61, p = .544, ns ; or commitment, t (5340) = -.45, p = .649, ns , in predicting each individual woman’s own ratings of these characteristics. Once again, these results suggest that the sexual coercion effects are not attributable to the tendency for fertile women to give more prototypic ratings with regard to all traits.

Discussion

This study tested whether women’s judgments of men’s sexual coerciveness change in systematic ways across the menstrual cycle. Based on the assumption that sexual assault would have been more costly when ancestral women were fertile, we predicted that women would show enhanced sensitivity to male sexual coerciveness during the fertile phase of their reproductive cycle.

As predicted, fertile women viewed men who were interviewed in a competitive, dating initiation situation as more coercive than did non-fertile women, consistent with the evolutionary-based notion that fertile women should err on the side of caution when evaluating men’s potential coerciveness. Also as predicted, fertile women’s judgments of men’s sexual coerciveness were better predicted by the average woman’s ratings of sexual coerciveness than were the judgments of non-fertile women. This supports the idea that, when fertile, women should be more attuned to salient cues of potential coerciveness that most women tend to see and less distracted by other features that are not reliably associated with coerciveness (or at least its perception).

Demonstrating special design demands that other, more general processes do not account for hypothesized effects. In this study, we found no evidence for a general tendency for fertile women to perceive different levels (or be selectively attuned to cues) of three male characteristics central to mate selection: kindness, commitment, and faithfulness. This suggests that the reported effects may be specific to perceptions of potential male sexual coerciveness, as implied by our evolutionary hypothesis.

Another possibility is that shifts in perceptions of male coercion are driven by increases in general fear at mid-cycle. In fact, previous work does not indicate that women experience either greater fear or generalized anxiety during the peri-ovulatory phase of

their cycle. If anything, feelings of greater fear and anxiety increase in the late luteal phase of the cycle (Solis-Oritz & Cabrera, 2002; Vandermolen, Merckelbach, & Vandenhout, 1988).

Nevertheless, these findings are novel and require replication. Future studies could bolster confidence in a cognitive feature specially designed to adaptively bias perceptions of men’s sexual coerciveness by demonstrating even greater specificity than was done here. For instance, a study that rules out the possibility that women are more sensitive to any form of coercion (sexual or otherwise) mid-cycle would elegantly demonstrate specificity of design. Once the existence of a cyclically shifting bias in women’s sexual coercion perceptions is more firmly established, the next step is to identify the mediating cues used by women to make their assessments and to determine how women are differentially using cues across the menstrual cycle.

Macrae, Alnwick, Milne, and Schloerscheidt (2002) have found that, when in the fertile phase of their cycle, women categorize men’s faces as “male” more rapidly and are more readily primed to process masculine personality traits and features (see also Johnston, Arden, Macrae, & Grace, 2003). This research importantly demonstrates social-cognitive changes across the menstrual cycle, but Macrae et al. did not provide a specific selectionist rationale for why one should expect the particular changes they document. One possible way Macrae et al.’s effects intersect with the current findings is that masculine facial features and traits are more salient to women because they are used to judge men’s coercive tendencies. In other words, our selectionist notions might indirectly explain the Macrae et al. findings. The current results illustrate the value of an evolutionary approach for investigating human sexual coercion and for identifying specific psychological mechanisms that may have evolved in women to combat male coercion.

Author Notes: The authors thank Martie Haselton, Geoffry Miller, Randy Thornhill, and Ron Yeo for insightful discussion on the ideas contained in this article and for providing helpful comments on earlier versions of this paper.

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Because slopes are a function of standard deviations and correlations, one might wonder whether the slopes were greater for fertile women simply because their responses were more widely distributed. In fact, the standard deviations of women’s sexual coerciveness ratings did not covary with their conception risk, r = .074, ns .

*

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