Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Elizabeth Kyonka

Committee Co-Chair

Miranda N. Reed

Committee Member

Claire C. St. Peter


Three pigeons were trained on concurrent-chain schedules. Concurrent variable-interval initial links produced fixed-interval (FI) terminal links. Occasional `no-food' terminal links were interspersed pseudorandomly to obtain stop times, a single-trial measure of temporal discrimination. In rapid-acquisition conditions, terminal links were FI 10 s and FI 20 s. Across sessions, the location of the initial link leading to the shorter terminal link varied pseudorandomly. Both terminal links were FI 15 s in a uniform condition. In the rapid-acquisition conditions, initial-link response allocation tracked relative terminal-link immediacy and stop times tracked terminal-link FIs. Initial- and terminal-link pecking stabilized within the first half of sessions. By contrast, initial-link response allocation adjusted to FI 15-s terminal links in uniform sessions relatively gradually, only after several sessions. Although choice adjusted relatively slowly, stop times adjusted and stabilized within a few sessions for two out of three pigeons. Residuals from separate regressions of log initial-link response ratios and log stop time ratios on log terminal-link immediacy ratios were positively correlated in rapid-acquisition conditions but not systematically related in the uniform condition. This pattern of residual covariation indicates that the relation between mechanisms that determine choice and timing was moderated by environmental dynamics.