A method for mapping stimulus distance into reinforcement value

Abstract

Three pigeons were trained to peck for grain on a five-ply multiple variable interval (VI) schedule of reinforcement. A different VI schedule was associated with each of the five orthogonal training stimuli. A vertical line (90°) was associated with the highest rate of reinforcement (VI 15 sec). Subsequent paired-comparison choice tests revealed that the training stimuli were chosen in direct relation to the reinforcement frequency of each of them. More importantly, the proportions of choice of line orientations other than the 90° line, when paired with the training stimuli and with each other, reflected both similarity to the 90° line and reinforcement frequency in the training. The line closest to 90° was chosen in preference to any of the other line test stimuli and to most of the orthogonal training stimuli by all birds. The other line test stimuli could similarly be located at some point on the reinforcement frequency continuum of the training stimuli. The data were interpreted in terms of expected probabilities of reinforcement which may be produced directly by actual frequencies of reinforcement associated with individual stimuli or indirectly as in stimulus generalization. The data suggested the possibility of mapping a stimulus distance variable, such as line orientation, into a reinforcement variable such as frequency of reinforcement.