Christensen, D.R. & Grace, R.D. (2009).
Response allocation in concurrent chains when terminal-link delays follow an ascending and descending series.
Journal of the Experimental Analysis of Behavior, 91, 1-20.
Eight pigeons were trained in a concurrent-chains procedure in which the terminal-link immediacy ratio followed an ascending or descending series.
Across sessions, one terminal-link delay changed from 2 s to 32 s to 2 s or from 32 s to 2 s to 32 s, while the other was always 8 s. Response
allocation for all pigeons tracked changes in the delay; was biased toward the 8-s alternative on the descending series, indicating a hysteresis
effect; and was more sensitive to changes in the terminal-link delay ratio for relatively long (> 8 s) than short (< 8 s) delays. Both the hysteresis
and effect of delay duration were predicted by an extended version of Grace and McLean’s (2006) decision model. The extended decision model provided
an overall better account of the results than a simple linear-operator model (Grace, 2002), and holds promise for an integrated account of choice in
concurrent chains for both acquisition and steady-state conditions.
Key words: reinforcer delay, acquisition, hysteresis, terminal-link effect, concurrent chains, choice, pigeons