The effects of amount of training per reversal on successive reversals of a color discrimination

Three groups of pigeons were trained on a red-green discrimination in which the stimuli were alternately presented in a multiple schedule of reinforcement. The discrimination was reversed 24 times. Groups were given 1, 2, or 4 hr of training on each discrimination. Increasing the length of training had two principal effects on reversal performance: it increased the rate of extinction of responding to one of the stimuli and increased the rate of reacquisition of responding to the other. The latter effect involved both an increase in reacquisition of responding to a positive stimulus within reversals and an increase in recovery of responding to the previous negative stimulus between reversals. Improvements in performance of each group over the series of reversals were qualitatively similar to the two effects of length of training on each discrimination, and were analogous to effects obtained in other studies involving overtraining and successive reversals of simultaneous discriminations.     

Inhibition of return using location discrimination in two age groups

The present study investigated "inhibition of return" which refers to increased response latency when the target in a location discrimination task appears in the same location on consecutive trials. Research to date has suggested that this effect is little changed across age. However, this study, which compared 12 older adults in good health (M=73.0, SD=5.3) with younger adults using the target-target paradigm to examine inhibition of return, suggests there is a strong and continuous effect in older adults in comparison to younger adults. Results indicate the possibility that the inhibitory function may become stronger at an older age.     

Diazepam-induced impairment of a go-no go successive discrimination

Diazepam (2.0 and 4.0 mg/kg, but not 1.0 mg/kg) administered in eight acquisition sessions significantly impaired the light-cued successive discrimination of male Sprague-Dawley rats. In two postdrug (vehicle) sessions, groups previously treated with the drug demonstrated good recovery in discrimination. An analysis of response components indicated that the impairment was due to the failure of drugged subjects to inhibit or withhold responses during the no go periods of the task. These findings are consistent with a "disinhibitory hypothesis" of drug impairment. The similarity of the present findings to those previously reported with chlordiazepoxide suggests that such effects are a generalized characteristic of the benzodiazepine class of drugs.