Elsevier

Evolution and Human Behavior

Volume 31, Issue 5, September 2010, Pages 320-325
Evolution and Human Behavior

Original Article
Humans show mate copying after observing real mate choices

https://doi.org/10.1016/j.evolhumbehav.2010.02.001Get rights and content

Abstract

When searching for a mate, one must gather information to determine the mate value of potential partners. By focusing on individuals who have been previously chosen by others, one's selection of mates can be influenced by another's successful search—a phenomenon known as mate copying. We show mate copying in humans with a novel methodology that closely mimics behavioral studies with non-human animals. After observing instances of real mating interest in video recordings of speed-dates, both male and female participants show mate copying effects of heightened short-term and long-term relationship interest towards individuals in dates they perceived as successful. Furthermore, the relative attractiveness of observers and observed plays a mediating role in whom an individual will choose to copy.

Introduction

In mate choice, in order to determine the value of potential mates individuals must gather information. One source of such information is the mate decisions of others. By focusing on potential mates (or their particular qualities) who have been chosen by others, mate choices can be influenced by another's successful search. This process, known as mate copying (Dugatkin, 1992, Dugatkin, 2000), has been widely documented in many animal species, mostly birds (Freed-Brown and White, 2009, Galef, 2008, Galef and White, 1998) and fish (Alonzo, 2008, Dugatkin, 1992). While many people may feel that their choice of a mate is an intensely personal and individual process, biologists have hypothesized that mate copying could also be present in humans (Brown and Fawcett, 2005, Dugatkin, 2000), and recent research has supported this idea (Eva and Wood, 2006, Jones et al., 2007Little et al., 2008, Waynforth, 2007); it may also underlie other sexual interactions including mate poaching (Schmitt & Buss, 2001). In non-human animals, mate copying has been studied primarily in the decision making of females, who are allowed to observe the courtship displays of males and the selections made among those males by their female peers. In humans, however, where mate choice decisions are typically mutual, men and women alike are choosing mates and being selective based on cues of mate value, particularly for long-term mating decisions (Todd and Miller, 1999, Todd et al., 2007). Thus, it is reasonable to expect that using social information could inform the decisions of both men and women, as has been found for animals with mutual mate choice (Frommen, Rahn, Schroth, Waltschyk, & Bakker, 2008). However, studies looking for these effects in humans have yielded mixed results, with some finding mate copying in both sexes (Little et al., 2008), while others found differences between the sexes (Hill & Buss, 2008), pointing to the need for further experimentation and perhaps new experimental designs.

Despite the present surge of interest in human mate copying, all of the studies published to date do not incorporate a key component of this phenomenon: the necessity of accurately determining whether an individual being observed has chosen a particular other individual as a mate. For mate copying to make adaptive use of social information, the focal (observer) individual has to know when the model (the observed individual of the same sex as the observer) actually has mating interest towards the target (the opposite-sex observed individual); otherwise, the observer could copy an instance of non-interest and thereby make a poor mate choice decision.

Current paradigms to test mate copying in humans obviate the need for an observer to infer a model's mating interest, by presenting observers with a single explicit cue of a model's romantic interest or attraction toward each target. This has been done, for instance, by labeling photos of a target and model side-by-side as “in a relationship” (Eva and Wood, 2006, Little et al., 2008, Waynforth, 2007) or by showing photos of targets paired with smiling opposite sex models (Jones et al., 2007). This approach means that participants learn about the status of a relationship through social communication, bringing along with it issues of the authority and believability of the source of that communication (e.g., the experimenter). Each study has a somewhat different presentation methodology, but most compare pre-test or baseline ratings of attractiveness to ratings obtained in conditions where mating interest is present. This can involve comparing ratings of photos labeled as single or in a relationship, seen by different subjects (Eva & Wood, 2006), or comparing unlabeled paired photos to labeled paired photos, within subjects (Waynforth, 2007), or comparing photos shown alongside attentive smiling versus neutral-expression members of the opposite sex, within subjects (Jones et al., 2007). Researchers then analyze the differences between target attractiveness ratings made by observers before getting the mating information and after, to see whether the explicit cue of mating interest made the targets appear more attractive—an indication of mate copying. The study by Little et al. (2008) was different in that there was no control condition, and only pictures of paired couples were presented, with each picture being either masculinized or feminized to increase or decrease its attractiveness. The changes in observer interest toward the targets were then compared based on the degree of these morphological alterations.

In contrast, for non-human animal studies, researchers create settings where model and target individuals are able to interact naturally and make their own mate choices, which observers can witness in full (Dugatkin, 2000). Rather than the human studies' presentations of still photos of purported mates, whom the observers might perceive as not even being a legitimate realistic couple, the animal study stimuli are dynamic interactions with the full set of body motions, vocal calls, and other social signals that are integral to the species' courtship and mate choice process. Obviously, there is a large gap between the minimalistic stimuli used in human mate copying experiments and the rich environments of animal research. This could be important for interpreting the results of recent human experiments: Are typical processes and levels of human mate copying elicited via still photos and single explicit cues of mating interest? Would human participants engage in less or more mate copying if they had to infer that interest themselves on the basis of observing real social interactions? Bridging the gap in experimental design by using more realistic presentations of interpersonal mating interest would give us a fuller understanding of when and how human mate copying happens in the real world, and could help overcome the small (or null) effect sizes and sometimes contradictory results of existing studies (Eva and Wood, 2006, Hill and Buss, 2008, Jones et al., 2007, Little et al., 2008, Uller, 2003, Waynforth, 2007).

To surmount the restrictions of using pictures of individuals as stimuli, we presented our participants with video clips of pairs of actual singles on real speed-dates. This allowed two key changes in methodology: First there were no explicit interest labels, and instead participants were told to judge the couples' interest in the interactions. Therefore instead of comparing judgments based on assigned categories (such as single or in a relationship), we can compare ratings based on how the participants perceived the success of the interactions. Second, by using video clips, participants were able to see and hear actual human mate choice interactions, so that multiple cues including tone of voice and nonverbal behavior could influence their interest judgments and their own ratings of the targets—and, hence, any mate copying that might occur. In addition, similar to the methodology of Little et al. (2008), we used measures of short-term and long-term relationship interest toward the targets (instead of just physical attractiveness ratings) to better understand when mate copying is used in mate choice.

Speed-dating as a research design aims to simulate initial mating relationship encounters at zero acquaintance, and since it is usually done with real singles and consequential choices, it does so more naturalistically than most other designs (Finkel et al., 2007, Penke et al., 2007).While speed-dating does not reflect mate choices that develop out of existing social relationships (e.g., friendships or work relationships), it likely captures a process involving newly encountered individuals that is relevant to many modern-day mate choice decisions and that could also have been important (even if infrequent) in our evolutionary past. Furthermore, it is analogous to laboratory mate copying work with other species where researchers use individuals who are not socially familiar with each other, and these results have been found to generalize to behavior in nature (Alonzo, 2008).

Mate copying could function as a shortcut for learning about features relevant to an individual animal's mate value that are not fully observable at first glance (Hill & Ryan, 2006), a possibility that has also been proposed for humans (Little et al., 2008). While studies have shown that valid information on all kinds of characteristics relevant for mate choice, including not only physical traits but also personality traits and intelligence (Borkenau, Mauer, Riemann, Spinath, & Angleitner, 2004) and socioeconomic status (Kraus & Keltner, 2009), can be gathered from short observations, these quick initial judgments vary in accuracy. Since the accuracy of person judgments increases over time with acquaintance (Biesanz et al., 2007, Funder and Colvin, 1988), the accuracy of first impressions could be improved by combination with the impressions formed by others over longer periods of interaction with the target individual. In line with this, models of adaptive mate copying situations in monogamous species predict the highest rates of copying when females can be sure that others have had enough time to learn about and judge males (Dubois, 2007). Additionally, social information (and mate copying) could be used to determine social popularity and prestige, which are typically more prominent in short-term mate choice (Buss & Schmitt, 1993). In either case, the decision to copy another's mate selection could stem from simply the presence of same-sex interest, or it could involve assessing the mate values of the model and target, or even how the model's and target's mate values compare to that of the observer (Hill and Ryan, 2006, Vukomanovic and Rodd, 2007; and see discussion in Vakirtzis and Roberts, 2009, Witte and Godin, 2010). To test for these possibilities, we first gathered independently rated attractiveness measures of the models and targets as proxies for their mate value, and then used these values to test whether observers blindly copied the selections of all models or if they were affected by absolute model mate value. We also compared model and target attractiveness ratings to self-attractiveness ratings made by the observers to see if the relative mate value of models and targets influenced observers' mate copying.

In sum, we designed this study to look for effects of mate copying in both short-term and long-term mate choice, by both sexes, and among targets, models, and observers with different absolute and relative mate values. While we expected both men and women to utilize mate copying because both sexes need to gather information on potential mates that might not be available on first glance to make adaptive mate choice decisions, the manner in which they are influenced by the social information could differ.

Section snippets

Participants

Observers comprised 40 women (mean age 20.0) and 40 men (mean age 19.8) recruited from the Indiana University psychology participant pool and compensated with course credit. All were over 18 years old, heterosexual, and with no knowledge of the German language (because the stimuli were in German; see next section).

Stimuli

We used photos of individuals and videos of the same individuals on speed-dates taken from the Berlin Speed Dating Study (BSDS), carefully controlled speed-dating sessions run at

Results

To look for mate copying effects, we assessed participant observers' change in their own romantic attraction to the opposite-sex speed dater targets as a consequence of the social information they perceived from watching the videos—that is, whether they thought the model was interested in the target. Fig. 1 presents these results for both short- and long-term relationship ratings made by male and female observers.

For rating changes for short-term relationships, both male and female observers

Discussion

We found that naturalistic stimuli of human romantic interest—videos of speed-dating interactions between real singles—led to robust mate copying effects, producing behavioral patterns not seen in previous studies. While some past research has shown mate copying only in women (Jones et al., 2007) and primarily for long-term relationships (Little et al., 2008), our results suggest that both men and women are influenced by social information when making both short-term and long-term relationship

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    This research was supported by grant As 59/15 of the German Research Foundation (DFG), awarded to Jens Asendorpf. Lars Penke is supported by the UK Medical Research Council (Grant No. 82800) and is part of The University of Edinburgh Centre for Cognitive Ageing and Cognitive Epidemiology. Funding from the BBSRC, EPSRC, ESRC and MRC is gratefully acknowledged. We would like to thank Marie-Luise Haupt, Karsten Krauskopf, Harald Schneider, and Sebastian Teubner for their help with the Berlin Speed Dating Study.

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