Level and mechanisms of perceptual learning: Learning first-order luminance and second-order texture objects

Vision Research 46 (2006) 1996–2007

Barbara Anne Dosher a,*, Zhong-Lin Lu

Memory, Attention, and Perception (MAP) Laboratory, Department of Cognitive Sciences, Institute of Mathematical Behavioral Sciences,
University of California, Irvine, CA 92697-5100, USA
b Laboratory of Brain Processes (LOBES), Departments of Psychology and Biomedical Engineering, and Neuroscience Graduate Program,
University of Southern California, Los Angeles, CA 90089-1061, USA

Abstract
Perceptual learning is an improvement in perceptual task performance reflecting plasticity in the perceptual system. Practice effects
were studied in two object orientation tasks: a first order, luminance object task and a second-order, texture object task. Perceptual learning
was small or absent in the first-order task, but consistently occurred for the second-order (texture) task, where it was limited to
improvements in low external noise conditions, or stimulus enhancement [Dosher, B., & Lu, Z. -L. (1998). Perceptual learning reflects
external noise filtering and internal noise reduction through channel reweighting. Proceedings of the National Academy of Sciences of the
United States of America, 95 (23) 13988–13993; Dosher, B., & Lu, Z. -L. (1999). Mechanisms of perceptual learning. Vision Research, 39
(19) 3197–3221], analogous to attention effects in first- and second-order motion processing [Lu, Z. -L., Liu, C. Q., & Dosher, B. (2000).
Attention mechanisms for multi-location first- and second-order motion perception. Vision Research, 40 (2) 173–186]. Perceptual learning
affected the later, post-rectification, stages of perceptual analysis, possibly localized at V2 or above. It serves to amplify the stimulus
relative to limiting internal noise for intrinsically noisy representations of second-order stimuli.