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.     

Temporal context in concurrent chains: I. Terminal-link duration

Two experiments are reported in which the ratio of the average times spent in the terminal and initial links (Tt/Ti) in concurrent chains was varied. In Experiment 1, pigeons responded in a three-component procedure in which terminal-link variable-interval schedules were in constant ratio, but their average duration increased across components by a factor of two. The log initial-link response ratio was a negatively accelerated function of Tt/Ti. Overall, the data were well described by Grace's (1994) contextual choice model (CCM) with temporal context represented as (Tt/Ti)k or 2Tt/(Tt + Ti), and by Mazur's (2001) hyperbolic value-added model (HVA), with each model accounting for approximately 93% of the variance. In Experiment 2, fixed-parameter predictions for each model were generated, based on the data from Experiment 1, for conditions in which Tt/Ti was varied over a more extreme range. Data were consistent with the predictions of CCM with temporal context represented as 2Tt/(Tt + Ti) and to a lesser extent as (Tt/Ti)k, but not with HVA. Overall, these results suggest that preference increases as a hyperbolic function of Tt/Ti when terminal-link duration is increased relative to initial-link duration, with the terminal-link schedule ratio held constant.     

Equivalent MIRID models

It is shown that in the context of the Model with Internal Restrictions on the Item Difficulties (MIRID), different componential theories about an item set may lead to equivalent models. Furthermore, we provide conditions for the identifiability of the MIRID model parameters, and it will be shown how the MIRID model relates to the Linear Logistic Test Model (LLTM). While it is known that the LLTM is a special case of the MIRID, we show that it is possible to construct an LLTM that encompasses the MIRID. The MIRID model places a bilinear restriction on the item parameters of the Rasch model. It is explained how this fact is used to simplify the results of Bechger, Verhelst, and Verstralen (2001) and Bechger, Verstralen, and Verhelst (2002), and extend their scope to a wider class of models.     

Thinking styles in relation to personality traits: an investigation of the Thinking Styles Inventory and NEO-PI-R

This study is an investigation of the Sternberg-Wagner Thinking Style Inventory (TSI), with regard to cross-cultural replication and relation to the five-factor personality model (FFM). TSI and NEO-PI-R were administered to 107 participants from USA and 114 participants from Norway. Inter-correlations between NEO-PI-R dimensions and TSI-scales and factors were not very strong, few exceeding 0.40, and the correlations were in predicted directions. Joint factor analyses of TSI and NEO-PI-R showed that TSI covers variance that NEO-PI-R does not explain. Thus, it is argued that the thinking styles give an independent contribution beyond FFM dimensions. However, TSI did not relate to FFM in the same manner in the two samples. Finally, the TSI-scales and factors were replicable across samples by Procrustes rotation. The question whether thinking style may be regarded as a valid and reliable construct is discussed.     

Crime, Social Capital, and Community Participation

Social disorganization at the neighborhood and community levels has been consistently linked to various forms of criminal activity. However, a very much smaller body of literature addresses the effects of crime on community organizations. In some studies, crime appears to energize communities while in others, crime leads to withdrawal from community life. Using department of health crime victimization data and interviews with 2,985 low-income inner city residents living in 487 multi-family dwellings, a multi-level model examined the relationships among crime victimization, social organization, and participation in neighborhood organizations. Social organization at the individual and building levels was measured using recent formulations of social capital theory. Findings regarding crime suggested more signs of a chilling effect on participation than of an energizing effect, especially at the building level. Social capital at the building level was more strongly and consistently related to participation in community organizations than was crime.     

Dynamic response-by-response models of matching behavior in rhesus monkeys

We studied the choice behavior of 2 monkeys in a discrete-trial task with reinforcement contingencies similar to those Herrnstein (1961) used when he described the matching law. In each session, the monkeys experienced blocks of discrete trials at different relative-reinforcer frequencies or magnitudes with unsignalled transitions between the blocks. Steady-state data following adjustment to each transition were well characterized by the generalized matching law; response ratios undermatched reinforcer frequency ratios but matched reinforcer magnitude ratios. We modelled response-by-response behavior with linear models that used past reinforcers as well as past choices to predict the monkeys' choices on each trial. We found that more recently obtained reinforcers more strongly influenced choice behavior. Perhaps surprisingly, we also found that the monkeys' actions were influenced by the pattern of their own past choices. It was necessary to incorporate both past reinforcers and past choices in order to accurately capture steady-state behavior as well as the fluctuations during block transitions and the response-by-response patterns of behavior. Our results suggest that simple reinforcement learning models must account for the effects of past choices to accurately characterize behavior in this task, and that models with these properties provide a conceptual tool for studying how both past reinforcers and past choices are integrated by the neural systems that generate behavior.     

DOES SENSITIVITY TO MAGNITUDE DEPEND ON THE TEMPORAL DISTRIBUTION OF REINFORCEMENT?

Our research addressed the question of whether sensitivity to relative reinforcer magnitude in concurrent chains depends on the distribution of reinforcer delays when the terminal-link schedules are equal. In Experiment 1, 12 pigeons responded in a two-component procedure. In both components, the initial links were concurrent variable-interval 40-s variable-interval 40-s, and the terminal links were both 20-s interval schedules in which responses were reinforced by either 4-s of grain in one, or 2-s of grain in the other. The only difference between the components was whether the terminal-link schedules were fixed interval or variable intervals. For all subjects, the relative rate of responding in the initial links for the terminal link that produced the 4-s reinforcer was greater when the terminal links were fixed-interval schedules than when they were variable-interval schedules. This result is contrary to the prediction of Grace's (1994) contextual choice model, but is consistent with both Mazur's (2001) hyperbolic value-added model and Killeen's (1985) incentive theory. In Experiment 2, 4 pigeons responded in a concurrent-chains procedure in which 4-s or 2-s reinforcers were provided independently of responding according to equal fixed-time or mixed-time schedules. Preference for the 4-s reinforcer increased as the variability of the intervals comprising the mixed-time schedules was decreased. Generalized-matching sensitivity of initial-link response allocation to relative reinforcer magnitude was proportional to the geometric mean of the terminal-link delays.     

Phonological and morphological consistency in the acquisition of vowel duration spelling in Dutch and German

In Dutch, vowel duration spelling is phonologically consistent but morphologically inconsistent (e.g., paar-paren). In German, it is phonologically inconsistent but morphologically consistent (e.g., Paar-Paare). Contrasting the two orthographies allowed us to examine the role of phonological and morphological consistency in the acquisition of the same orthographic feature. Dutch and German children in Grades 2 to 4 spelled singular and plural word forms and in a second task identified the correct spelling of singular and plural forms of the same nonword. Dutch children were better in word spelling, but German children outperformed the Dutch children in nonword selection. Also, whereas German children performed on a similar level for singular and plural items, Dutch children showed a large discrepancy. The results indicate that children use phonological and morphological rules from an early age but that the developmental balance between the two sources of information is constrained by the specific orthography.