Grace, R. C. & McLean, A. P. (2006).
Rapid acquisition in concurrent chains: Evidence for a decision model.
Journal of the Experimental Analysis of Behavior, 85, 181-
202.
Pigeons’ choice in concurrent chains can adapt to rapidly changing
contingencies. Grace, Bragason, and McLean (2003) found that relative initial-
link response rate was sensitive to the immediacy ratio in the current session
when one of the terminal-link fixed-interval schedules was changed daily
according to a pseudorandom binary sequence (e.g., Schofield and Davison, 1997).
The present experiment tested whether the degree of variation in delays across
sessions had any effect on acquisition rate in Grace et al.’s (2003) rapid-
acquisition procedure. In one condition (“minimal variation”), the left
terminal link was always fixed-interval 8 s and the right terminal link was
either fixed-interval 4 s or fixed-interval 16 s. In the other condition
(“maximal variation”), a unique pair of fixed-interval values was used in each
session. Responding was sensitive to the current-session immediacy ratio in
both conditions, but across subjects there was no systematic difference in
sensitivity. These results challenge the view that initial-link responding in
the rapid-acquisition procedure is determined by changes in the learned value of
the terminal-link stimuli, and suggests instead that a process resembling
categorical discrimination may control performance. A decision model based on
the assumption that delays are categorized as short or long relative to the
history of delays provided a good account of the data and shows promise in being
able to explain other choice phenomena.
Key words: choice, concurrent chains, rapid-acquisition procedure, conditioned
reinforcement value, generalized matching, categorical discrimination, key peck,
pigeons