Ploog, B. O. (2001).
Effects of primary reinforcement on pigeons’ initial-link responding under a concurrent-chains schedule with nondifferential terminal links.
Journal of the Experimental Analysis of Behavior,
76, 75-94.
The effect of primary reinforcement on initial-link responding
under concurrent-chains schedules with nondifferential terminal
links was assessed in 12 pigeons. The initial and terminal links
were variable-interval schedules (always the same for both
alternatives). The positions (left or right key) of the
initial-link stimuli (red or green) were randomized while the
correlation between color and food amount remained constant
within each condition. The terminal-link stimuli were always
presented on the center key. Except in two control groups and
conditions, the terminal-link stimuli were the same color
(nondifferential, blue or yellow). Over six conditions, the
differences in food amount and the durations of the initial- and
terminal-link schedules were manipulated. In 57 of 60 cases,
birds generated choice proportions above .50 in favor of the
initial-link stimulus that was correlated with the larger
reinforcer. There was some indication that preference increased
with shortened terminal-link durations. Because the terminal-link
stimuli were nondifferential, differential responding in the
initial links cannot be explained easily by conditioned
reinforcement represented by the terminal-link stimuli. Thus,
primary reinforcement has a direct effect on initial-link
responding in concurrent-chains schedules.
Key words: primary reinforcement, conditioned reinforcement,
choice, memory marking, reinforcement magnitude,
concurrent-chains schedules, pigeon