درک علمی جذابیت فیزیکی زنان و سلامت

Using realistic three-dimensional female body models, we found evidence for a categorical perception of female physical attractiveness and health in male and female Caucasian observers. In a rating task, we showed that these bodies were rated for attractiveness or health in the same way as real bodies. In a two-alternative forced-choice task, we showed that these bodies were categorized into attractive vs. unattractive or healthy vs. unhealthy nonlinearly, which allowed us to estimate the position of a categorical boundary between attractive and unattractive or healthy and unhealthy bodies. In a delayed match-to-sample task, we measured the sensitivity of discrimination between pairs of bodies. We found significantly better discrimination for pairs that crossed the attractive/unattractive or healthy/unhealthy boundary than pairs that did not, even though the physical changes in both conditions were identical. Thus, categorical perception enhances the perception of physical changes that cross the boundary between discrete perceptual categories of important judgments such as attractiveness or health, which can be a cue for mate selection.

One of the most fundamental problems facing individuals is mate selection. Thus, it is important that they have a means to efficiently evaluate the attractiveness of potential partners because the wrong choice will have a negative impact on their reproductive success (Buss, 2006 and Zebrowitz and Rhodes, 2002). As attractiveness can be a cue to fitness and reproductive potential, we might expect very strong selective pressures for the development of perceptual mechanisms that effectively evaluate attractiveness. It is generally assumed that body attractiveness judgments are graded along a continuum from attractive to unattractive through a series of intermediate levels (e.g., Fan et al., 2004, Swami et al., 2006, Swami et al., 2007, Thornhill and Grammer, 1999, Tovée et al., 1998 and Tovée et al., 2002). However, it is perceptually demanding to make fine-grain judgments of physical attractiveness. To simplify such judgments so that appropriate responses can be acted upon, a potentially more effective approach would be to initially assign bodies into discrete perceptual categories, such as attractive or unattractive. This kind of categorical perception is well documented for many aspects of perception. For example, facial identity (e.g., Beale and Keil, 1995, Levine and Beale, 2000 and Rotshtein et al., 2005), gender (e.g., Webster, Kaping, Mizokami, & Duhamel, 2004), facial expressions (e.g., Calder et al., 1996 and Etcoff and Magee, 1992) and race (e.g., Cosmides et al., 2003 and Levine and Angelone, 2002) all show categorical perception. However, little research has examined categorical perception for evolutionary fitness cues, such as attractiveness. In the current study, we examined the extent to which observers perceive female physical attractiveness and health categorically and how this categorical perception, if present, affects observers' ability to discriminate body shapes. A key feature of categorical perception is that although an observer will be very sensitive to changes occurring across a boundary between two perceptual categories (such as between attractive and unattractive bodies), observers will be much less sensitive to the same amount of physical changes in stimuli if they occur within a perceptual category (such as discriminating among bodies that are all attractive). A well-known example of categorical perception is the recognition of human facial expressions. We are very good at distinguishing the changes in facial feature configurations that push a facial expression across a categorical boundary, such as between happy and sad, but we are much less sensitive to the same amount of changes in facial configuration within a category, such as happy (e.g., Calder et al., 1996, de Gelder et al., 1997, Etcoff and Magee, 1992 and Young et al., 1997). Categorical perception would allow a more accurate classification of bodies into attractive vs. unattractive or healthy vs. unhealthy categories but necessarily reduces finer-grain judgments within a perceptual category. However, in reproductive terms, the important strategy is to avoid unattractive partners, who are potentially unhealthy and nonfertile. Discrimination within categories is still possible but less important. If partner choice is from an “attractive pool”, all of the potential outcomes should be a reasonably good choice. Indeed, given an individual's limited neural processing resources, it would make sense to sacrifice within-category shape sensitivity to improve across-category shape sensitivity. Thus, categorical perception could enhance the accuracy of health judgments. To investigate how observers perceive female physical attractiveness and health, we systematically manipulated realistic female body models to alter their level of fatness from underweight to obese. Previous studies have suggested that altering apparent body fat will alter the attractiveness and perceived health level of the female bodies (e.g., Smith et al., 2007, Tovée et al., 1999 and Tovée et al., 2007). Following Calder et al.'s (1996) paradigm, male and female observers were asked to perform various perceptual tasks: a rating task, a two-alternative forced-choice task and a delayed match-to-sample (DMS) task. The rating task allowed us to compare the pattern of attractiveness or health ratings with previous studies to confirm that the body models were rated in the same way as real bodies. The forced-choice task forced observers to either categorize bodies as attractive vs. unattractive or healthy vs. unhealthy, which allowed us to estimate the position of the putative categorical boundary. The DMS task allowed us to test whether there was an improved perceptual performance in discriminating between female bodies across this categorical boundary, which has been shown to exist in categorical studies using faces (e.g., Calder et al., 1996).