Abstract
The present experiment was designed to investigate the effects of successive shifts in N-length in a simple instrumental task. A recent theory (Capaldi, Note 1) predicts positive contrast effects due to a shift from a longer to a shorter N-length and negative contrast resulting from the opposite shift. Two groups of rats were given seven trials per day, four of which were rewarded, in a straight alley. One group was trained using an N-length of three, and the other using an N-length of one. After 20 days, one-half of each group was shifted to the opposite N-length for an additional 20 days, while the remainder of the animals continued as in the first phase for this period. Finally, all four groups received 5 days of extinction. There was no evidence for either positive or negative contrast. In addition, there were no group differences during the extinction phase. The data did not support the predictions generated by the rein-forcement level theory.
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Walkenbach, J., Haddad, N.F. & Mellgren, R.L. N-length shifts and successive contrast effects. Bull. Psychon. Soc. 11, 83–85 (1978). https://doi.org/10.3758/BF03336772
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DOI: https://doi.org/10.3758/BF03336772