Learning about environmental geometry: a flaw in Miller and Shettleworth's (2007) operant model

Many studies have examined how humans and other animals reestablish a sense of direction following disorientation in enclosed environments. Results showing that geometric shape of an enclosure is typically encoded, sometimes to the exclusion of featural cues, have led to suggestions that geometry might be encoded in a dedicated geometric module. Recently, Miller and Shettleworth (2007) proposed that the reorientation task be viewed as an operant task and they presented an associative operant model that appears to account for many empirical findings from reorientation studies. In this paper we show that, although Miller and Shettleworth's insights into the operant nature of the reorientation task may be sound, their mathematical model has a serious flaw. We present simulations to illustrate the implications of the flaw. We also propose that the output of a simple neural network, the perceptron, can be used to conduct operant learning within the reorientation task and can solve the problem in Miller and Shettleworth's model.     

Velocity discrimination: reliability and construct validity in older adults

The aim of this study was to determine whether a test of velocity discrimination is a reliable and valid measure of proprioception in healthy older adults. Results revealed excellent test-retest reliability over a 2-week period. Velocity discrimination also indicated good construct validity with modest correlations with center of pressure sway outcomes in eyes open and closed conditions as well as stair climbing time. Good construct validity was identified by velocity discrimination sensitivity to age with a higher mean value for the older participants than for the younger participants. These findings suggest velocity discrimination is a valid and reliable measure of velocity sense, which may be included with measures of position and movement sense to enhance the proprioceptive testing repertoire among researchers. Implications of these results are discussed in terms of evaluation of proprioceptive training programs aimed to enhance postural control.     

Examination of the MMPI-2 Restructured Clinical (RC) Scales in a Sample of Bariatric Surgery Candidates

The current study examined the MMPI-2 Restructured Clinical (RC) scales (Tellegen et al., MMPI-2 Restructured Clinical (RC) scales: Development, validation, and interpretation. Minneapolis: University of Minnesota Press, 2003) in a sample of 1,091 bariatric surgery candidates. The RC scales were developed to address concerns about limited discriminant validity of the Clinical scales. Internal consistency and external validity analyses were conducted to evaluate the RC scales in this setting. Results indicated that the RC scales are generally more internally consistent than the Clinical scales and display significantly better convergent and discriminant validity in predicting a variety of behavioral, psychological, and developmental variables relevant to preoperative bariatric psychological evaluations. Implications of the results and recommendations for future research with the RC scales in medical settings are discussed.     

Mere exposure and the endowment effect on consumer decision making

Previous researchers (e.g., J. A. Bargh, 1992, 2002) demonstrated the importance of nonconscious processes on consumer choice behavior. Using an advertisement, the authors determined the effect of two nonconscious processes--the mere exposure effect, which increases object preference by increasing consumer exposure to an object, and the endowment effect, which increases object valuation by providing consumer possession of an object--on consumer behavior. Although the mere exposure effect and endowment effect did not produce an interaction, they produced independent effects. The endowment effect increased object valuation but not object preference. The mere exposure effect increased object preference but not object valuation. Thus, at the unconscious level, an increase in object preference does not lead to an increase in object valuation, nor does an increase in object valuation lead to an increase in object preference. The authors discuss the importance of developing measures of unconscious process in advertising effectiveness.     

Collaboration during visual search

Two experiments examine how collaboration influences visual search performance. Working with a partner or on their own, participants reported whether a target was present or absent in briefly presented search displays. We compared the search performance of individuals working together (collaborative pairs) with the pooled responses of the individuals working alone (nominal pairs). Collaborative pairs were less likely than nominal pairs to correctly detect a target and they were less likely to make false alarms. Signal detection analyses revealed that collaborative pairs were more sensitive to the presence of the target and had a more conservative response bias than the nominal pairs. This pattern was observed even when the presence of another individual was matched across pairs. The results are discussed in the context of task-sharing, social loafing and current theories of visual search.