Document Detail

Within-trial contrast: when you see it and when you don't.
MedLine Citation:
PMID:  18318423     Owner:  NLM     Status:  MEDLINE    
Within-trial contrast occurs when a discriminative stimulus that is preceded by a relatively aversive event is preferred over another that is preceded by a less aversive event. Recent failures to replicate (Arantes & Grace, 2008; Vasconcelos, Urcuioli, & Lionello-DeNolf, 2007) may allow us to identify factors that may be responsible. In the case of Vasconcelos et al., it is likely that insufficient training was provided (often 35-65 sessions are required). In the case of Arantes and Grace (Experiment 2), these pigeons had been involved in prior experiments involving lean schedules of reinforcement, and we find that prior experience its occurrence. with lean (relatively aversive) schedules appears to reduce the presumed aversiveness of the many-peck requirement, thus obviating the contrast effect. Finally, in the case of Vasconcelos and Urcuioli (2008), although the contrast effect with a simultaneous discrimination was not reliable, it was not reliably smaller than with a successive discrimination that did show a reliable effect, and the contrast effect was also similar in magnitude to a reliable effect reported by Kacelnik and Marsh (2002). Thus, although there have been several failures to replicate the original effects reported by Clement, Feltus, Kaiser and Zentall (2000), insufficient training, prior history with lean schedules of reinforcement, and low statistical power may have been responsible for those failures.
Thomas R Zentall
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Publication Detail:
Type:  Comment; Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Learning & behavior     Volume:  36     ISSN:  1543-4494     ISO Abbreviation:  Learn Behav     Publication Date:  2008 Feb 
Date Detail:
Created Date:  2008-03-05     Completed Date:  2008-07-09     Revised Date:  2011-01-24    
Medline Journal Info:
Nlm Unique ID:  101155056     Medline TA:  Learn Behav     Country:  United States    
Other Details:
Languages:  eng     Pagination:  19-22; discussion 23-8     Citation Subset:  IM    
Department of Psychology, University of Kentucky, Lexington, Kentucky 40506-0044, USA.
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MeSH Terms
Animal Experimentation / ethics*
Ethics, Professional*
Grant Support
Comment On:
Learn Behav. 2008 Feb;36(1):1-11   [PMID:  18318421 ]
Learn Behav. 2008 Feb;36(1):12-8   [PMID:  18318422 ]

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