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A representation is a remnant of previous experience that allows that experience to affect later behavior. This paper develops a metatheoretical view of representation and applies it to issues concerning representation in animals. To describe a representational system one must specify the following: the domain or range of situations in the represented world to which the system applies; the content or set of features encoded and preserved by the system; the code or transformational rules relating features of the representation to the corresponding features of the represented world; the medium, or the representation's physical instantiation; and the dynamics, or how the system changes with time. In part because of the behaviorist assumption that the hypothetical, covert changes occurring in an organism during learning correspond to the overt physical changes that are observed, issues of representation in animal behavior have been largely ignored as irrelevant or misleading. However, it can be inferred that representations, acting as models of environmental regularities, operate at many levels of behavioral functioning, both cognitive and noncognitive. Objections to the use of this concept in explanations of animal behavior, based on the claim that it is indeterminate and on behaviorist considerations of parsimony, can be answered. Animal representations may be specialized in terms of tasks and species. Data from tasks involving spatial memory, delayed matching-to-sample, and sequence learning suggest some foundations for a general theory of animal representations.

Empirical evidence of a relationship between combat-related PTSD and increased anger is lacking. In this study, 24 veterans of the Vietnam War with posttraumatic stress disorder (PTSD) scored significantly higher on an Anger factor comprising multiple measures of anger than did comparison groups of 23 well-adjusted Vietnam combat veterans and 12 noncombat Vietnam-era veterans with psychiatric diagnoses. In contrast, the 3 groups did not differ significantly on orthogonal factors, one of which comprised cognitive impulsivity measures and the other of which reflected motor impulsivity. Changes in heart rate in response to provocation loaded positively on the Anger factor and negatively on the 2 Impulsivity factors. Concurrent depression and trait anxiety did not have an effect on level of anger in individuals with PTSD. These empirical findings support and extend the clinical evidence regarding PTSD and anger.