Human operant learning under concurrent reinforcement of response variability

This study asked whether the concurrent reinforcement of behavioral variability facilitates learning to emit a difficult target response. Sixty students repeatedly pressed sequences of keys, with an originally infrequently occurring target sequence consistently being followed by positive feedback. Three conditions differed in the feedback given to non-target sequences: concurrent positive feedback presented contingent on response variability, positive feedback presented non-contingently, or no reinforcement for any non-target responses (control condition). Contrary to the result of analogous rat studies, if anything, the participants in the control condition more readily learned to emit the target sequence than did the subjects in each of the other two conditions. It is argued that these contradictory findings are primarily caused by procedural differences, such as differences in the density of the reinforcement schedule applied to non-target behavior, rather than reflecting a true species difference. (c) 2005 Elsevier Inc. All rights reserved

Burnout and Cortisol: Evidence for a Lower Cortisol Awakening Response in Both Clinical and Non-Clinical Burnout

Objective: Although the relationship between burnout and cortisol levels has been examined in previous studies, the results are mixed. By adopting a design in which we attempted to overcome important limitations of earlier research, the purpose of the present study was to improve the understanding of the biological underpinnings of burnout and to further the knowledge about the relationship between burnout and cortisol. Methods: A clinical burnout patient group (n = 32), a non-clinical burnout group (n = 29), and a healthy control group (n = 30) were compared on burnout symptoms, physical and psychological complaints, and on cortisol levels. In order to examine a broad range of cortisol indices, including different measures of the cortisol awakening response (CAR) and several day-curve measures, salivary cortisol was collected six times a day during two consecutive non-workdays. Results: As expected, the clinical burnout group reported more burnout symptoms, and physical and psychological complaints than the non-clinical burnout group, which in turn reported more burnout symptoms and physical and psychological complaints than the healthy control group. With regard to cortisol levels, we found that until 30 min after awakening, the CAR of both the clinical and the non-clinical burnout group was lower compared with the healthy control group. Furthermore, there was some evidence that the decline of cortisol during the day was smaller in the non-clinical burnout group than in the healthy control group. Conclusion: The results of the present study provide support for lowered cortisol in both clinical and non-clinical burnout

Varied but not necessarily random: Human performance under variability contingencies is affected by instructions

The goal of the present study was to evaluate the role of verbal stimuli in the production of response variability in humans. College students were distributed into three groups and asked to type three-digit sequences. Participants in the systematic group were instructed to produce sequences according to a rule of their choice; those in the random group were instructed to produce sequences according to chance; and those in the control group were not instructed about how to produce sequences. The experiment employed an ABA design. During the A phases, low-frequent sequences were reinforced (variability contingency), whereas during the B phase, reinforcement was withdrawn (extinction). The results indicated the following: (1) The instructions were efficient at producing systematic and random-like patterns for the systematic and random groups, respectively; in the absence of instructions, a mix of both patterns was observed. (2) Behavior was sensitive to extinction independently of the instructions provided. (3) Systematic patterns favored a more equiprobable distribution of sequences across trials. (4) Reaction times were longer for responding in a systematic than in a random-like fashion. The present findings suggest that individual differences in meeting variability contingencies may be due, at least partially, to instructional control