Concurrent-chain performance in transition: Effects of terminal-link duration and individual reinforcers

Abstract

Pigeons responded on concurrent-chain schedules with variable-interval initial links and equal delays as terminal links. The terminal-link delays were 1 sec in some conditions and 20 sec in other conditions. The percentages of reinforcers delivered for responses on the left key were 10%, 30%, 70%, or 90%, and this percentage was switched every five to nine sessions. The rate of change in the pigeons' response percentages after a switch was the same whether the terminal-link delays were 1 sec or 20 sec. Analysis of the effects of individual reinforcers showed that after a response on one key had been reinforced, response percentages on that key were higher for at least the next 100 responses. Small effects of individual reinforcers were evident after eight or nine additional reinforcers had been delivered. The effects of individual reinforcers were about equally large during times of transition and during periods in which overall response percentages were relatively stable.

Initial-link duration and acquisition of preference in concurrent chains

“…The reason for the apparent discrepancy is that Grace (2002a) used a design in which the schedules preceding and following the reversal were manipulated factorially, so that their effects could be assessed independently. According to the LINOP model, when the durations preceding and following the transition are the same, as in Mazur's (2002) study, their effects cancel out. Thus, the LINOP model is able to account for the results in both Grace's and Mazur's studies.…”

“…In his experiment, the terminal-link delays were equal (1 or 20 sec), and the percentage of terminal-link entries provided by the initial links was changed across conditions. Overall, Mazur (2002) found no effect of terminal-link duration on acquisition. Although initiallink response rates were much higher when the terminallink delays were 1 sec, the rate of change in preference was the same as in the 20-sec condition.…”

“…There is an apparent conflict in the results of Mazur (2002) and Grace (2002a), because Mazur found that acquisition rate did not depend on overall terminal-link duration, whereas Grace found that preference changed more rapidly when the durations were long preceding and short following the reversal. The reason for the apparent discrepancy is that Grace (2002a) used a design in which the schedules preceding and following the reversal were manipulated factorially, so that their effects could be assessed independently.…”

“…Mazur et al found that preference adjusted more rapidly after changes in the percentage of terminal links delivered by the initial links rather than when the terminal-link delays were switched. Mazur (2002)…”

The allocation of operant behavior.

“…Mazur et al found that preference adapted more rapidly when the proportion of entries arranged by the initial links was changed rather than when the terminal-link delays were changed. Mazur (2002a) studied whether acquisition of initial-link preference depended on overall terminal-link duration. In his experiment, terminal-link delays were equal (1 second or 20 seconds), and the proportion of terminal-link entries arranged by the initial links was changed.…”