Monkeys show recognition without priming in a classification task

• Type of Material: Article
• Authors: Benjamin Michael Basile, Emory University; Robert Hampton, Emory University
• Language: English
• Date: 2013-02
• Publisher: Elsevier
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2012 Elsevier B.V. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.beproc.2012.08.005
• Title of Journal or Parent Work: Behavioural Processes
• ISSN: 0376-6357
• Volume: 93
• Start Page: 50
• End Page: 61
• Grant/Funding Information: This work was supported by NIH grant 1R01MH082819, NSF grant 0745573, the National Center for Research Resources P51RR000165, the Office of Research Infrastructure Programs / OD P51OD011132, and by the Center for Behavioral Neuroscience under the STC Program of the NSF under Agreement IBN-9876754.
• Keywords: repetition priming; amnesia; nondeclarative memory; categorization; implicit memory
• Research Categories: Psychology, Behavioral

Abstract

Humans show visual perceptual priming by identifying degraded images faster and more accurately if they have seen the original images, while simultaneously failing to recognize the same images. Such priming is commonly thought, with little evidence, to be widely distributed phylogenetically. Following Brodbeck (1997), we trained rhesus monkeys (Macaca mulatta) to categorize photographs according to content (e.g., birds, fish, flowers, people). In probe trials, we tested whether monkeys were faster or more accurate at categorizing degraded versions of previously seen images (primed) than degraded versions of novel images (unprimed). Monkeys categorized reliably, but showed no benefit from having previously seen the images. This finding was robust across manipulations of image quality (color, grayscale, line drawings), type of image degradation (occlusion, blurring), levels of processing, and number of repetitions of the prime. By contrast, in probe matching-to-sample trials, monkeys recognized the primes, demonstrating that they remembered the primes and could discriminate them from other images in the same category under the conditions used to test for priming. Two experiments that replicated Brodbeck’s (1997) procedures also produced no evidence of priming. This inability to find priming in monkeys under perceptual conditions sufficient for recognition presents a puzzle.