Geometric determinants of human spatial memory

Geometric alterations to the boundaries of a virtual environment were used to investigate the representations underlying human spatial memory. Subjects encountered a cue object in a simple rectangular enclosure, with distant landmarks for orientation. After a brief delay, during which they were removed from the arena, subjects were returned to it at a new location and orientation and asked to mark the place where the cue had been. On some trials the geometry (size, aspect ratio) of the arena was varied between presentation and testing. Responses tended to lie somewhere between a location that maintained fixed distances from nearby walls and a location that maintained fixed ratios of the distances between opposing walls. The former were more common after expansions and for cued locations nearer to the edge while the latter were more common after contractions and for locations nearer to the center. The spatial distributions of responses predicted by various simple geometric models were compared to the data. The best fitting model was one derived from the response properties of 'place cells' in the rat hippocampus, which matches the 'proximities' 1/(d+c) of the cue to the four walls of the arena, where d is the distance to a wall and c is a global constant. Subjects also tended to adopt the same orientation at presentation and testing, although this was not due to using a view matching strategy, which could be ruled out in 50% of responses. Disoriented responses were most often seen where the cued location was near the center of the arena or where the long axis of a rectangular arena was changed between presentation and testing, suggesting that the geometry of the arena acts as a weak cue to orientation. Overall, the results suggest a process of visual landmark matching to determine orientation, combined with an abstract representation of the proximity of the cued location to the walls of the arena consistent with the neural representation of location in the hippocampus.     

Cognitive style and plebe turnover at the U.S. Naval Academy

Students entering (N = 1,134) the U.S. Naval Academy class of 2000 were administered the Kirton Adaption-Innovation Inventory on the first day of Plebe Summer, a 7-wk. nonacademic training program completed by all entering students in the summer prior to the freshman year. The mean score on Innovation cognitive style for this sample of plebes was approximately a standard deviation lower than those of five other undergraduate student samples from nonmilitary universities. Furthermore, the 98 plebes who voluntarily withdrew before completing the program scored higher on the average on Innovation than those who remained. Findings suggest that, in terms of Person-Organization fit, plebes with a more innovative cognitive style may, perhaps, be less compatible with the regimentation-style climate of the Academy than those with an Adaptive cognitive style. Further research, however, is needed to specify the relationship between Academy students' cognitive style and other important organizational outcomes.     

The English lexicon of interpersonal affect: Love, etc

Three studies were conducted to determine some aspects of the semantic structure of words referring to positive interpersonal affect. Two studies determined dimensions of difference and families of related words on the basis of the target persons associated with each. These results were compared with those from sorting on the basis of overall similarity of meaning. There was close agreement among the three studies, using different samples of words, indices of similarity, and judges. The relation of the similarity structure of the words to the dimensions of affective experience and to discrete, basic, emotion is discussed.     

Outcome additivity and outcome maximality influence cue competition in human causal learning

Recent research suggests that outcome additivity pretraining modulates blocking in human causal learning. However, the existing evidence confounds outcome additivity and outcome maximality. Here the authors present evidence for the influence of presenting information about outcome maximality (Experiment 1) and outcome additivity (Experiment 2) on subsequent forward blocking. The results of Experiment 3 confirm that, with outcome maximality controlled, outcome additivity affects backward blocking but not release from overshadowing. Finally, the results of Experiment 4 demonstrate that information about outcome additivity has a similar effect on forward blocking if presented after the blocking training instead of before. The results are compatible with the idea that blocking results from inferential processes at the time of testing and not from a failure to acquire associative strength during training.     

Further evidence for the role of mode-independent short-term associations in spatial Simon effects

We examined the conditions under which short-term associations between stimuli and responses can produce spatial Simon effects. On location-relevant trials, participants gave neutral responses (i.e., they uttered the nonsense syllable "bee" or "boo") on the basis of whether the presented word had the meaning of "left" or "right." On location-irrelevant trials, they gave the same responses on the basis of the color of left and right squares. Performance on the location-irrelevant trials was affected by the match between the irrelevant location information and the location to which the correct response was assigned on the location-relevant trials. Experiment 1 showed that this extrinsic Simon effect was found only when the words on the location-relevant trials came from two different languages. In Experiment 2, we found an extrinsic Simon effect even when participants only received instructions about how to respond on location-relevant trials but no such trials were actually presented. Our findings suggest that task demands determine whether short-term associations are mode specific or mode independent and confirm that such associations can be set up as the result of instructions only.     

Distances appear different on hills

When walking effort is increased due to manipulations such as wearing heavy backpacks, people perceive hills to be steeper and distances to be farther (Bhalla & Proffitt, 1999; Proffitt, Stefanucci, Banton, & Epstein, 2003). On the basis of these findings, we expected people to overestimate distances on steep hills relative to the same distances on flat ground, because of the increased effort required to ascend or descend them. This hypothesis is in contrast to the belief that distances are specified solely by optical and oculomotor information related to the geometry of the environment. To test the hypothesis, we investigated distance estimation on hills and flat terrains in natural and virtual environments. We found that participants judged steep uphill and downhill distances to be farther than the same distances on flat terrain. These results are inconsistent with the idea that spatial layout is perceived solely in terms of geometry, lending partial support to an effort hypothesis.     

Timely Completion of Class Requirements: Effects of Student and Faculty Gender

Male and female students have displayed different reactions to the gender of their faculty. This research was designed to explore whether biases exist early in the school term. Students unfavorable attitudes toward instructors were measured by the extent to which they delayed completing a course requirement: participation in a subject pool. Students scheduled a date upon which to participate in a research study. Discrepancies between their scheduled and their actual participation dates reveal that male students delayed their requirement (a) more when their instructors were female than when they were male, and (b) more than female students when the instructors were female. Supporting data suggest that the delayed completion time reflects lower evaluations of female faculty. Discussion focuses on implications in academic settings.     

Interacting neighbors: A connectionist model of retrieval in single-digit multiplication

For most adults, retrieval is the most common way to solve a single-digit multiplication problem (Campbell & Xue, 2001). Many theories have been proposed to describe the underlying mechanism of arithmetical fact retrieval. Testing their validity hinges on evaluating how well they account for the basic findings in mental arithmetic. The most important findings are the problem size effect (small multiplication problems are easier than larger ones; cf. 3 x 2 and 7 x 8), the five effect (problems with 5 are easier than can be accounted for by their size), and the tie effect (problems with identical operands are easier than other problems; cf. 8 x 8 and 8 x 7). We show that all existing theories have difficulties in accounting for one or more of these phenomena A new theory is presented that avoids these difficulties. The basic assumption is that candidate answers to a particular problem are in cooperative/competitive interactions and these interactions favor small, five, and tie problems. The theory is implemented as a connectionist model, and simulation data are described that are in good accord with empirical data.     

Assessing the informational value of parameter estimates in cognitive models

Mathematical models of cognition often contain unknown parameters whose values are estimated from the data. A question that generally receives little attention is how informative such estimates are. In a maximum likelihood framework, standard errors provide a measure of informativeness. Here, a standard error is interpreted as the standard deviation of the distribution of parameter estimates over multiple samples. A drawback to this interpretation is that the assumptions that are required for the maximum likelihood framework are very difficult to test and are not always met. However, at least in the cognitive science community, it appears to be not well known that standard error calculation also yields interpretable intervals outside the typical maximum likelihood framework. We describe and motivate this procedure and, in combination with graphical methods, apply it to two recent models of categorization: ALCOVE (Kruschke, 1992) and the exemplar-based random walk model (Nosofsky & Palmeri, 1997). The applications reveal aspects of these models that were not hitherto known and bring a mix of bad and good news concerning estimation of these models.