Mazur, J. E. (1999).
Preferences for and against stimuli paired with food.
Journal of the Experimental Analysis of Behavior,
72, 21-32.
Pigeons were presented with a concurrent-chains schedule in
which terminal-link entries were assigned to two response keys on
a percentage basis. The terminal links were fixed delays that
sometimes ended with food and sometimes did not. In most
conditions, 80% of the terminal links were assigned to one key,
but a smaller percentage of the terminal links ended with food
for this key, so the number of food reinforcers delivered by the
two alternatives was equal. When the same terminal-link stimuli
(orange houselights) were used for both alternatives, the pigeons
showed a preference for whichever alternative delivered more
frequent terminal links. When different terminal-link stimuli
(green vs. red houselights) were used for the two alternatives,
the pigeons showed a preference for whichever alternative
delivered fewer terminal links when terminal-link durations were
long, and no systematic preferences when terminal-link durations
were short. This pattern of results was consistent with the
predictions of Grace's (1994) contextual choice model. Preference
for the alternative that delivered more frequent terminal links
was usually stronger in the first few sessions of a condition
than at the end of a condition, suggesting that the conditioned
reinforcing effect of the additional terminal-link presentations
was, in part, transitory.
Key words: conditioned reinforcement, choice, concurrent chains,
reinforcement probability, key peck, pigeons