Prairie dog alarm calls encode labels about predator colors

Some animals have the cognitive capacity to differentiate between different species of predators and generate different alarm calls in response. However, the presence of any addition information that might be encoded into alarm calls has been largely unexplored. In the present study, three similar-sized human females walked through a Gunnison’s prairie dog (Cynomys gunnisoni) colony wearing each of three different-colored shirts: blue, green, and yellow. We recorded the alarm calls and used discriminant function analysis to assess whether the calls for the different-colored shirts were significantly different. The results showed that the alarm calls for the blue and the yellow shirts were significantly different, but the green shirt calls were not significantly different from the calls for the yellow shirt. The colors that were detected, with corresponding encoding into alarm calls, reflect the visual perceptual abilities of the prairie dogs. This study suggests that prairie dogs are able to incorporate labels about the individual characteristics of predators into their alarm calls, and that the complexity of information contained in animal alarm calls may be greater than has been previously believed.     

Automatic quantity processing in 5-year olds and adults

In this study adults performed numerical and physical size judgments on a symbolic (Arabic numerals) and non-symbolic (groups of dots) size congruity task. The outcomes would reveal whether a size congruity effect (SCE) can be obtained irrespective of notation. Subsequently, 5-year-old children performed a physical size judgment on both tasks. The outcomes will give a better insight in the ability of 5-year-olds to automatically process symbolic and non-symbolic numerosities. Adult performance on the symbolic and non-symbolic size congruity tasks revealed a SCE for numerical and physical size judgments, indicating that the non-symbolic size congruity task is a valid indicator for automatic processing of non-symbolic numerosities. Physical size judgments on both tasks by children revealed a SCE only for non-symbolic notation, indicating that the lack of a symbolic SCE is not related to the mathematical or cognitive abilities required for the task but instead to an immature association between the number symbol and its meaning.     

Colours sometimes count: awareness and bidirectionality in grapheme-colour synaesthesia

Three experiments were conducted with 10 grapheme-colour synaesthetes and 10 matched controls to investigate (a) whether awareness of the inducer grapheme is necessary for synaesthetic colour induction and (b) whether grapheme-colour synaesthesia may be bidirectional in the sense that not only do graphemes induce colours, but that colours influence the processing of graphemes. Using attentional blink and Stroop paradigms with digit targets, we found that some synaesthetes did report “seeing” synaesthetic colours even when they were not able to report the inducing digit. Moreover, congruency effects (effects of matching the colour of digit presentation with the synaesthetic colour associated with that digit) suggested that grapheme-colour synaesthesia can be bidirectional, at least for some synaesthetes.     

Subtyping and social consensus: the role of the audience in the maintenance of stereotypic beliefs

Two studies investigated the effect of stereotypes held by a prospective audience on participants' reactions to a stereotype‐disconfirming member. In Study 1, participants formed an impression of a positive disconfirming gay in order to communicate it to an audience known to hold a negative versus positive stereotype about gays. As predicted, participants subtyped the deviant more in the former than in the latter case. Moreover, participants' stereotype at the end of the study mirrored the audience's assumed stereotypes about gays. In Study 2, participants learned about a stereotype allegedly held by an ingroup or an outgroup audience about Belgians and then received information about a Belgian who disconfirmed the stereotype. As predicted, the deviant was seen as less typical when he violated the stereotype held by an ingroup than by an outgroup audience. Also, participants' stereotype about Belgians was more similar to the one held by the ingroup audience. A mediational analysis confirmed that participants subtyped the disconfirming member in order to embrace the stereotype advocated by the ingroup audience. Results are discussed in light of recent models of stereotype change. Copyright © 2006 John Wiley & Sons, Ltd.     

A Meta-Analysis of the Distinction between Reactive and Proactive Aggression in Children and Adolescents

The present meta-analytic review aimed to clarify divergent findings concerning the relation between reactive and proactive aggression in children and adolescents. Fifty-one studies with 17,965 participants were included in the analysis. A significant correlation between reactive and proactive aggression was found. The strength of this relation varied considerably between studies, from -.10 to .89. Observational assessment and tilt/noise tasks were associated with smaller correlations than questionnaires. Within the large group of questionnaire studies, studies disentangling the form and function of aggression found lower correlations than studies that did not disentangle form and function. Among questionnaire studies, higher reliability was associated with larger correlations. Effect size did not depend on other study characteristics such as sample type, age, and informant type. It is concluded that reactive and proactive aggression are most clearly distinguished with behavioral observations and questionnaires that unravel form and functions of aggression.