The Functional Form of Performance Improvements in Perceptual Learning Learning Rates and Transfer

Barbara Anne Dosher1 and Zhong-Lin Lu2
1Department of Cognitive Science, University of California, Irvine, and 2Department of Psychology, University of Southern
California

PSYCHOLOGICAL SCIENCE
Volume 18—Number 6

ABSTRACT—
The functional form of performance improvements
has been extensively studied in speeded cognitive
and motor tasks; in such tasks, reductions in response
times have been characterized by the ubiquitous power law
of learning or by a simpler exponential form. Performance
improvements in perceptual capacities are also important
in expertise, but their functional form is unknown. This
study investigated the functional form of perceptual
learning. For individual observers, reductions in thresholds
were best described by an exponential function, rather
than a power or compound exponential and power (apex)
function. Learning was specific to orientation, a result
that supports the perceptual locus of the learning, and was
decoupled in high and low external noise, a result that
reflects separable learning mechanisms in the two conditions.
The simple exponential form of learning implies a
constant relative rate of learning throughout practice;
there was no evidence supporting multilevel hypotheses,
such as serial reverse hierarchical and parallel-learning
models, that posit multiple processes of learning characterized
by different rates.