See erratum,
JEAB, 2005, 83, 220.
Grace, R. C. & Bragason, O. (2005).
Does sensitivity to magnitude depend on the temporal distribution of reinforcement?
Journal of the Experimental Analysis of Behavior, 83, 169-184.
Our research addressed the question of whether sensitivity to relative reinforcer
magnitude in concurrent chains depends on the distribution of reinforcer delays
when the terminal-link schedules are equal. In Experiment 1, 12 pigeons responded
in a two-component procedure. In both components, the initial links were
concurrent variable-interval 40 s variable-interval 40 s, and the terminal
links were both 20-s interval schedules in which responses were reinforced
by either 4 s of grain in one, or 2 s of grain in the other. The only
difference between the components was whether the terminal-link schedules
were fixed interval or variable intervals. For all subjects, the relative
rate of responding in the initial links for the terminal link that produced
the 4-s reinforcer was greater when the terminal links were fixed-interval
schedules than when they were variable-interval schedules. This result is
contrary to the prediction of Grace’s (1994) contextual choice model, but
is consistent with both Mazur’s (2001) hyperbolic value-added model and
Killeen’s (1985) incentive theory. In Experiment 2, 4 pigeons responded
in a concurrent-chains procedure in which 4-s or 2-s reinforcers were
provided independently of responding according to equal fixed-time or
mixed-time schedules. Preference for the 4-s reinforcer increased as
the variability of the intervals comprising the mixed-time schedules
was decreased. Generalized-matching sensitivity of initial-link
response allocation to relative reinforcer magnitude was proportional
to the geometric mean of the terminal-link delays.
Key words: reinforcer magnitude, concurrent chains, contextual choice model,
hyperbolic value added model, incentive theory, key peck, pigeons