Spatial Overshadowing in Pigeons: Evidence for an Acquisition Deficit

We investigated theoretical accounts of spatial overshadowing using a landmark-based spatial-search task in a touchscreen preparation with pigeons. Pigeons first learned to find a hidden target on a screen using a compound of two visual cues as landmarks. Landmark A was proximal to the target while landmark X was distal to the target. Experiment 1 replicated our prior spatial overshadowing effect whereby landmark A overshadowed the development of spatial control by X. Spatial control by X was also poorer than by landmark Y which had been paired with the target alone but with the same absolute distance to the target as X had. Thus, the poor spatial control by X was not merely due to the greater X-target distance (relative to the A-target distance). Experiments 2a and 2b failed to find recovery from spatial overshadowing of X through either post-training extinction or counterconditioning of overshadowing landmark A, respectively. We interpret our results as being consistent with acquisition-focused models of elementary associative learning, but not with performance-focused models.

Acquisition of Secondary Reinforcers by Children

In one partially reinforced and one continuously reinforced group, children made no response during training. One partially reinforced group picked up and ate candy which was presented contiguously with a light. One partially and one continuously reinforced group picked up the candy but did not eat it. One control group received no candy during training trials, and a second control group received no training. Extinction tests with the light contingent upon lever excursion indicated that a response during acquisition was not necessary to condition a secondary reinforcer, but strong effects were obtained by including a consummatory response. Stronger effects were obtained with a partial schedule and either no response or a consummatory response during acquisition trials.