The development of stimulus control with and without a lighted key

Auditory stimulus control in pigeons: Jenkins and Harrison (1960) revisited

Pigeons were trained to peck a key in the presence of a 1000-Hz tone on a variable-interval one-minute schedule of reinforcement. One group was trained with an illuminated key; the other was trained in a totally dark chamber. During a generalization test on tonal frequency, subjects trained and tested with the key illuminated produced rather shallow gradients around the training value; subjects trained and tested in the dark produced steeper generalization gradients. These data replicate Jenkins and Harrison's (1960) finding that tone acquires relatively little control over responding and demonstrate that this absence of control is a function of the presence of the keylight.

The failure of stimulus control after presence-absence discrimination of click-rate

Pigeons were trained to discriminate a slow click-rate from its absence, or to discriminate it from a faster click-rate. Subsequent click-rate generalization tests produced the usual steepened gradients after the intradimensional discrimination but produced flat gradients after presence/absence discrimination. The occurrence of stimulus control only after intradimensional discrimination, combined with previous results showing stimulus control sometimes after nondifferential reinforcement and sometimes after presence/absence discrimination, argues for a reformulation of the problem of stimulus control. A theoretical framework, relying upon blocking effects inherent in the different discrimination procedures, was presented to account for the diversity of results.

Conditional discrimination training and interocular transfer in pigeons

Four groups of pigeons were trained either monocularly or binocularly on a series of successive line orientation discriminations. The role in interocular transfer of both changes in viewing conditions and background cues was examined. Either red or green background illumination to the patterns was used as changes in background cues; whereas alterations in viewing conditions were obtained by transferring from binocular to monocular vision, or from the left to the right eye. The results suggest that the viewing condition can operate in the same way as an external cue does for a conditional discrimination. This finding provides an explanation of the learning of conflicting discriminations with each eye by animals that also show interocular transfer.