Pigeons worked in a titrating delay match-to-sample (TDMTS) procedure in which selecting the correct comparison stimulus increased the delay between sample offset and comparison-array onset and incorrect comparison selections decreased that delay. Prior research in our lab has shown that the stable adjusted value of the retention interval is a curvilinear function of the observing response requirement. The current study examined the effect of the distribution and predictability of observing response requirements on adjusted retention interval values. The data show that unpredictable observing response requirements were more effective in attenuating the deleterious effects of delay on matching accuracy. The data have implications for our understanding of attending and encoding in performances involving remembering over short temporal durations.

Pigeons were trained on a zero-delay identity match-to-sample task. Experiment 1 started with every correct match reinforced with grain access and subsequent conditions include higher fixed-ratio values. Experiment 2 included the same fixed-ratio values as experiment 1 with and without a limited hold (LH) on the opportunity to select a comparison stimulus. Prior research suggested that trials after reinforcement would have an increased likelihood of error, and that these errors would be reduced in LH conditions. Results confirmed this expected error pattern and in most LH conditions errors were reduced early in the ratio.

Attempts to control various aspects of response requirements and sample viewing durations of sample stimuli show that an increase in both facilitates acquisition of conditional discriminations. Despite these attempts, few empirical data exist that demonstrate the relative contributions of both response- and time-dependent schedules. In addition, viewing opportunities of sample stimuli are present outside of the researchers' control, allowing for 'unauthorized sample viewing.' This study employed a titrating delay matching-to-sample procedure to systematically control various aspects of response requirements and sample viewing durations to independently assess their relative contributions towards conditional discrimination performance. Four pigeons worked on a titrating delay matching-to-sample procedure in which the delay between sample offset and comparison onset continuously adjusted as a function of the accuracy of the pigeons' choices. Results show sample viewing durations contribute most toward conditional discrimination performance. The data show 'unauthorized sample viewing' improved acquisition of conditional discriminations and should be a consideration in design of future research.

Four experimentally naïve white Carneau pigeons learned to match three colors to each other in a variant of an Identity matching-to-sample procedure with an FR20 on samples and a response-initiated FI8-s on comparisons. In Experiment 1, the extent to which subjects were matching on the basis of identity was assessed by presenting, in extinction, test trials comprising novel stimuli serving as the sample (and matching comparison) or as the nonmatching comparison. The results from Experiment 1 suggested intermediate or little to no transfer on the basis of identity. Experiment 2 reassessed transfer on the basis of identity with differential reinforcement on the test trials. Under these conditions, two of the four birds demonstrated substantially better than chance levels of performance. These data imply that while the extended response requirements may be necessary, other procedural aspects may be responsible for generalized identity matching in the pigeon.

A common procedural variation that facilitates the acquisition of conditional discriminations is to increase the time an organism spends in the presence of the sample stimulus by programming extended sample-observing response requirements. Despite their common use, there has been little empirical investigation of the effects of extended sample-observing response requirements. In the current study, four pigeons worked on a titrating delay matching-to-sample procedure in which the delay between sample offset and comparison onset was adjusted as a function of the pigeons' accuracy. The number of responses required to produce the comparison array was manipulated across conditions. Results show that all subjects were able to withstand longer delays between sample offset and comparison onset as sample-observing response requirements increased. These data show that the extent of the response requirement in the presence of the sample has systematic effects on conditional discrimination performances and should be considered in the design of experiments.