Generalization of cross-modal stimulus equivalence classes: operant processes as components in human category formation.

This study employed a stimulus-class rating procedure to explore whether stimulus equivalence and stimulus generalization can combine to promote the formation of open-ended categories incorporating cross-modal stimuli. A pretest of simple auditory discrimination indicated that subjects (college students) could discriminate among a range of tones used in the main study. Before beginning the main study, 10 subjects learned to use a rating procedure for categorizing sets of stimuli as class consistent or class inconsistent. After completing conditional discrimination training with new stimuli (shapes and tones), the subjects demonstrated the formation of cross-modal equivalence classes. Subsequently, the class-inclusion rating procedure was reinstituted, this time with cross-modal sets of stimuli drawn from the equivalence classes. On some occasions, the tones of the equivalence classes were replaced by novel tones. The probability that these novel sets would be rated as class consistent was generally a function of the auditory distance between the novel tone and the tone that was explicitly included in the equivalence class. These data extend prior work on generalization of equivalence classes, and support the role of operant processes in human category formation.     

Matching under nonindependent variable-ratio schedules of drug reinforcement.

Response-contingent deliveries of oral pentobarbital maintained responding of 3 rhesus monkeys during daily 3-hr sessions. Deliveries of pentobarbital were arranged under nonindependent concurrent variable-ratio variable-ratio schedules. Responses to either schedule counted toward completion of both variable-ratio schedule requirements. This schedule is similar in some respects to conventional concurrent variable-interval variable-interval schedules, in which passage of time counts toward completion of the interval value on both schedules. Restricted nonindependent concurrent variable-ratio variable-ratio schedules were also studied. On that schedule, when a drug delivery was assigned to one spout, it had to be collected before responses on the opposite spout again counted toward completion of the schedule requirements. Relative reinforcer magnitude was varied by changing the drug concentration on one schedule while keeping the drug concentration constant on the other variable-ratio schedule. Under both types of concurrent variable-ratio schedules, the relative rate of responding corresponded to the relative drug intake. Unlike earlier studies of concurrent variable-interval variable-interval intravenous cocaine reinforcement, preference was proportionate to concentration, and exclusive preferences did not develop. The relationship between relative rate of responding and relative drug intake was well described by the generalized matching law.     

Response acquisition with delayed reinforcement: a comparison of two-lever procedures.

Groups of 8 experimentally naive rats were exposed during 8-hr sessions to resetting delay procedures in which responses on one lever (the reinforcement lever) produced water after a delay of 8, 16, 32, or 64 s. For rats in one condition, responses on a second (no-consequences) lever had no programmed consequences. For rats in another condition, responses on a second (cancellation) lever during a delay initiated by a response on the reinforcement lever prevented delivery of the scheduled reinforcer; responses on the cancellation lever at other times had no programmed consequences. Under both conditions and at all delays, most subjects emitted more responses on the reinforcement lever than did control rats that never received water emitted on either lever. At 8-s delays, both conditions engendered substantially more responding on the reinforcement lever than on the other lever, and performance closely resembled that of immediate-reinforcement controls. At delays of 16 and 32 s, however, there was clear differential responding on the two levers under the cancellation condition but not under the other condition. When the delay was 64 s, differential responding on the two levers did not occur consistently under either condition. These findings provide strong evidence that the behavior of rats is sensitive to consequences delayed by 8, 16, and 32 s, but only equivocal evidence of such sensitivity to consequences delayed 64 s. They also indicate that acquisition depends, in part, on the measure of performance used to index it.     

Reasoning ability in older adults measured through letter and number series

Letter series and number series tests, consisting of items based on identical rules, were administered in a counterbalanced design to 58 persons (46 women and 12 men) between the ages of 61 and 88 years to determine their relative efficacy (relative difficulty and acceptability) as measures of inductive/deductive reasoning ability. Results indicated that letter and number series tests, in which each item in one has a same-rule counterpart in the other, were not equivalent in regard to their relative difficulty or popularity among the elderly. The number series test was significantly (p 0001) easier and more popular than its letter series counterpart. Some of the implications of these findings for assessing reasoning ability in the elderly were specified.     

Auditory perception of relative distance of traffic sounds

This study examines the accuracy of judgements of relative distance of traffic sounds (car and lorry) compared with nonattributed sounds (white noise). Adults judged whether sounds were comparatively nearer or further away in both conditions when decibel levels were the same and when decibel levels differed. Results indicated that judgement of relative distance is generally difficult and that such judgements are not based on loudness alone, particularly for traffic sounds. More errors were made when decibel levels were the same, indicating a reluctance to rely on loudness as an indicator of distance. Also more errors were made for traffic sounds. It was suggested that nonauditory criteria may be used in interpreting sounds, possibly including past experience and visual imagery. Finally, the implications of the results for road safety are discussed.     

Multilevel modeling in industrial and personnel psychology

Many of the topics of interest in the social and behavior sciences are often hierarchical or multilevel in nature. These multiple levels (e.g., individual versus group) create problems for researchers related to the choice of measurement and analysis. Recent innovations in statistical analysis have made it possible to account for the hierarchical nature of observations. Therefore, in this article we begin with a review of multilevel analysis techniques and discuss advances that have been made in the social sciences using multilevel models. Next, we summarize contemporary research specific to the organizational psychology literature that uses multilevel analysis. Possible applications for industrial and personnel psychology are then discussed. Guidelines for determining if multilevel analysis is appropriate for a given applied research project are provided. We conclude with a summary and call for increased use of multilevel analysis in industrial and personnel psychology.     

Earman on Underdetermination and Empirical Indistinguishability

Earman (1993) distinguishes three notions of empirical indistinguishability and offers a rigorous framework to investigate how each of these notions relates to the problem of underdetermination of theory choice. He uses some of the results obtained in this framework to argue for a version of scientific anti- realism. In the present paper we first criticize Earman's arguments for that position. Secondly, we propose and motivate a modification of Earman's framework and establish several results concerning some of the notions of indistinguishability in this modified framework. Finally, we interpret these results in the light of the realism/anti- realism debate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Different Training Procedures Recruit Either One or Two Critical Periods for Contextual Memory Consolidation, Each of Which Requires Protein Synthesis and PKA

We have used a combined genetic and pharmacological approach to define the time course of the requirement for protein kinase A (PKA) and protein synthesis in long-term memory for contextual fear conditioning in mice. The time course of amnesia in transgenic mice that express R(AB) and have genetically reduced PKA activity in the hippocampus parallels that observed both in mice treated with inhibitors of PKA and mice treated with inhibitors of protein synthesis. This PKA- and protein synthesis-dependent memory develops between 1 hr and 3 hr after training. By injecting the protein synthesis inhibitor anisomycin or the PKA inhibitor Rp-cAMPs at various times after training, we find that depending on the nature of training, contextual memory has either one or two brief consolidation periods requiring synthesis of new proteins, and each of these also requires PKA. Weak training shows two time periods of sensitivity to inhibitors of protein synthesis and PKA, whereas stronger training exhibits only one. These studies underscore the parallel dependence of long-term contextual memory on protein synthesis and PKA and suggest that different training protocols may recruit a common signaling pathway in distinct ways.