Davison, M. & Baum, W.M. (2006).
Do conditional reinforcers count?
Journal of the Experimental Analysis of Behavior, 86, 269-283.
Six pigeons were trained on a procedure in which seven components arranged
different food-delivery ratios on concurrent variable-interval schedules each
session. The components were unsignaled, lasted for 10 food deliveries, and
occurred in random order with a 60-s blackout between components. The schedules
were arranged using a switching-key procedure in which two responses on a
center key changed the schedules and associated stimuli on two side keys.
In Experiment 1, over five conditions, an increasing proportion of food
deliveries accompanied by a magazine light was replaced with the presentation
of the magazine light only. Local analyses of preference showed preference
pulses toward the alternative that had just produced either a
food-plus-magazine-light or magazine-light-only presentation,
but pulses after food deliveries were always greater than those
after magazine lights. Increasing proportions of magazine lights
did not change the size of preference pulses after
food or magazine-light presentations. Experiment 2 investigated
the effects of correlations between food ratios and magazine-light
ratios: In Condition 6, magazine-light ratios in components were
inversely correlated (-1.0) with food ratios, and in Condition 7,
magazine-light ratios were uncorrelated with food ratios. In
Conditions 8 and 9, pecks also produced occasional 2.5-s flashes
of a green keylight. In Condition 8, food and magazine-light
ratios were correlated 1.0 whereas food and green-key ratios
were correlated -1.0. In Condition 9, food and green-key
ratios were correlated 1.0 whereas food and magazine-light ratios
were correlated -1.0. Preference pulses toward
alternatives after magazine lights and green keys
depended on the correlation between these event
ratios and the food ratios: If the ratios were
correlated +1.0, positive preference pulses resulted;
if the correlation was -1.0, preference pulses were
negative. These results suggest that the Law of E
ffect has more to do with events signaling consequences
than with strengthening responses.
Key words: choice, concurrent schedules, preference pulses,
reinforcement, conditional reinforcement, pecking, pigeons