Working memory: Trouble in mind

AbstractVisual working memory has been found to depend on interactions between the prefrontal cortex and visual association areas; the neurons involved can be modulated by dopamine. These new findings have relevance for the treatment of Parkinson's disease and schizophrenia

Humans are not fooled by size illusions in attractiveness judgements

Could signallers use size contrast illusions to dishonestly exaggerate their attractiveness to potential mates? Using composite photographs of women from three body mass index (BMI) categories designed to simulate small groups, we show that target women of medium size are judged as thinner when surrounded by larger women than when surrounded by thinner women. However, attractiveness judgements of the same target women were unaffected by this illusory change in BMI, despite small true differences in the BMIs of the target women themselves producing strong effects on attractiveness. Thus, in the context of mate choice decisions, the honesty of female body size as a signal of mate quality appears to have been maintained by the evolution of assessment strategies that are immune to size contrast illusions. Our results suggest that receiver psychology is more flexible than previously assumed, and that illusions are unlikely to drive the evolution of exploitative neighbour choice in human sexual displays. © 2014 The Authors

Can we believe judgements of human physical attractiveness?

A key question in attractiveness studies is the validity of the reported results outside the narrow confines of the experimental paradigm used. Does the range of physical features in a set of pictures used to test attractiveness judgments predict the individual ratings of each body? Or does each stimulus have an attractiveness value independent of the range of attractiveness found in the image set of which it is a part? An additional problem is that because participants are often shown a relatively large array of images in a short space of time, this may produce perceptual biases which could cause a short-term shift in attractiveness preferences which are not usually found in real life mate choice decisions. To address this issue we asked 20 participants (10 male and 10 female) to judge the attractiveness of 20 digital photographs of female bodies. We then asked a different set of 400 people (who had not seen the body pictures) to judge the attractiveness of one of the bodies from the set (so each body was rated in isolation by 10 male and 10 female participants). We then compared the attractiveness judgement each body received when seen independently versus when it was seen within the context of a set of bodies. The results showed no significant difference between the two conditions which suggests that each body has an attractiveness value independent of the attractiveness of the other bodies with which it is viewed

Patterns of eye-movements when Male and Female observers judge female attractiveness, body fat and waist-to-hip ratio

Behavioural studies of the perceptual cues for female physical attractiveness have suggested two potentially important features; body fat distribution (the waist-to-hip ratio or WHR) and overall body fat (often estimated by the body mass index or BMI). However none of these studies tell us directly which regions of the stimulus images inform observers’ judgments. Therefore, we recorded the eye-movements of 3 groups of 10 male observers and 3 groups of 10 female observers, when they rated a set of 46 photographs of female bodies. The first sets of observers rated the images for attractiveness, the second sets rated for body fat and the third sets for WHR. If either WHR and/or body fat are used to judge attractiveness, then observers rating attractiveness should look at those areas of the body which allow assessment of these features, and they should look in the same areas when they are directly asked to estimate WHR and body fat. So we are able to compare the fixation patterns for the explicit judgments with those for attractiveness judgments, and infer which features were used for attractiveness. Prior to group analysis of the eye-movement data, the locations of individual eye fixations were transformed into a common reference space to permit comparisons of fixation density at high resolution across all stimuli. This manipulation allowed us to use spatial statistical analysis techniques to show: 1) Observers’ fixations for attractiveness and body fat clustered in the central and upper abdomen and chest, but not the pelvic or hip areas, consistent with the finding that WHR had little influence over attractiveness judgments. 2) The pattern of fixations for attractiveness ratings was very similar to the fixation patterns for body fat judgments. 3) The fixations for WHR ratings were significantly different from those for attractiveness and body fat

BMI Not WHR Modulates BOLD fMRI Responses in a Sub-Cortical Reward Network When Participants Judge the Attractiveness of Human Female Bodies

In perceptual terms, the human body is a complex 3d shape which has to be interpreted by the observer to judge its attractiveness. Both body mass and shape have been suggested as strong predictors of female attractiveness. Normally body mass and shape co-vary, and it is difficult to differentiate their separate effects. A recent study suggested that altering body mass does not modulate activity in the reward mechanisms of the brain, but shape does. However, using computer generated female body-shaped greyscale images, based on a Principal Component Analysis of female bodies, we were able to construct images which covary with real female body mass (indexed with BMI) and not with body shape (indexed with WHR), and vice versa. Twelve observers (6 male and 6 female) rated these images for attractiveness during an fMRI study. The attractiveness ratings were correlated with changes in BMI and not WHR. Our primary fMRI results demonstrated that in addition to activation in higher visual areas (such as the extrastriate body area), changing BMI also modulated activity in the caudate nucleus, and other parts of the brain reward system. This shows that BMI, not WHR, modulates reward mechanisms in the brain and we infer that this may have important implications for judgements of ideal body size in eating disordered individuals

The influence of personal BMI on body size estimations and sensitivity to body size change in anorexia spectrum disorders

In this cross-sectional study, we investigated the influence of personal BMI on body size estimation in 42 women who have symptoms of anorexia (referred to henceforth as anorexia spectrum disorders, ANSD), and 100 healthy controls. Low BMI control participants over-estimate their size and high BMI controls under-estimate, a pattern which is predicted by a perceptual phenomenon called contraction bias. In addition, control participants' sensitivity to size change declines as their BMI increases as predicted by Weber's law. The responses of women with ANSD are very different. Low BMI participants who have ANSD are extremely accurate at estimating body size and are very sensitive to changes in body size in this BMI range. However, as BMI rises in the ANSD participant group, there is a rapid increase in over-estimation concurrent with a rapid decline in sensitivity to size change. We discuss the results in the context of signal detection theory

View-dependent accuracy in body mass judgements of female bodies

A fundamental issue in testing body image perception is how to present the test stimuli. Previous studies have almost exclusively used images of bodies viewed in front-view, but this potentially obscures key visual cues used to judge adiposity reducing the ability to make accurate judgements. A potential solution is to use a three-quarter view, which combines visual cues to body fat that can be observed in front and profile. To test this hypothesis, 20 female observers completed a 2-alternative forced choice paradigm to determine the smallest difference in body fat detectable in female bodies in front, three-quarter, and profile view. There was a significant advantage for three-quarter and profile relative to front-view. Discrimination accuracy is predicted by the saliency of stomach depth, suggesting that this is a key visual cue used to judge body mass. In future, bodies should ideally be presented in three-quarter to accurately assess body size discrimination

The Effect of Own Body Concerns on Judgments of Other Women’s Body Size

We investigated the relationships between healthy women’s estimates of their own body size, their body dissatisfaction, and how they subjectively judge the transition from normal to overweight in other women’s bodies (the “normal/overweight” boundary). We propose two complementary hypotheses. In the first, participants compare other women to an internalized Western “thin ideal,” whose size reflects the observer’s own body dissatisfaction. As dissatisfaction increases, so the size of their “thin ideal” reduces, predicting an inverse relationship between the “normal/overweight” boundary and participants’ body dissatisfaction. Alternatively, participants judge the size of other women relative to the body size they believe they have. For this implicit or explicit social comparison, the participant selects a “normal/overweight” boundary that minimizes the chance of her making an upward social comparison. So, the “normal/overweight” boundary matches or is larger than her own body size. In an online study of 129 healthy women, we found that both opposing factors explain where women place the “normal/overweight” boundary. Increasing body dissatisfaction leads to slimmer judgments for the position of the “normal/overweight” boundary in the body mass index (BMI) spectrum. Whereas, increasing overestimation by the observer of their own body size shifts the “normal/overweight” boundary toward higher BMIs

Men's perception of current and ideal body composition and the influence of media internalization on body judgements

Introduction: To determine men's body ideals and the factors that influence these choices, this study used a matrix of computer generated (CG) male bodies (based on an analysis of 3D scanned real bodies) which independently varied in fat and muscle content. Methods: Two hundred and fifty-eight male participants completed a range of psychometric measures to index body concerns and body ideal internalization and then chose the CG body that best reflected their own current body, as well as the body that reflected their personal ideal. A subset of participants was then retested to check that these judgements were stable over time. Results: While judgements of the ideal body seem to be influenced by a shared appearance ideal, the degree to which this ideal was internalized showed significant variability between participants. The effect of this internalization was reflected in the difference between the estimated current body and the ideal. Discussion: Higher internalization led to a preference for higher muscle and lower fat content. This preference was most marked for fat content, although reducing adiposity also made the underlying musculature more salient. Additionally, the ideal body composition was modulated by the composition the participant believed his current body had (i.e., it seemed that a participant's ideal body was anchored by what they believed to be their current body and what change was possible from this starting point)