Kangas, B.D. & Branch, M.N. (2008).
Empirical validation of a procedure to correct position and stimulus biases
in matching-to-sample.
Journal of the Experimental Analysis of Behavior, 90, 103-112.
The development of position and stimulus biases often occurs during
initial training on matching-to-sample tasks. Furthermore, without
intervention, these biases can be maintained via intermittent reinforcement
provided by matching-to-sample contingencies. The present study evaluated
the effectiveness of a correction procedure designed to eliminate both
position and stimulus biases. Following key-peck training, a group of 6
pigeons had extended exposure to matching-to-sample contingencies without
a correction procedure, a group of 4 pigeons was briefly exposed to a
simultaneous matching-to-sample procedure to assess biases prior to
exposure to the correction procedure, and a group of 5 pigeons was
exposed directly to the correction procedure. The correction procedure
arranged that every time an incorrect match was made, the trial configuration
was repeated on the subsequent trial until a correct match was made.
Extended exposure to matching-to-sample contingencies without a correction
procedure was associated with reduced biases eventually for most subjects,
but rapid development of near-perfect accuracy and bias-free performance was
observed upon the implementation of the correction procedure regardless of
the type of bias. Bias-free performance was maintained following subsequent
exposure to a zero-delay MTS procedure.
Key words: position bias, stimulus bias, correction procedure, matching-to-sample, pigeons