Stimulus control in pigeons based on proprioceptive stimuli from floor inclination.

Two groups of pigeons trained to peck a dimly illuminated disc in an otherwise dark experimental chamber with the floor horizontal (0 degrees tilt) or inclined 30 degrees to the left, respectively, show decremental generalization gradients of response rate when the floor inclination is varied from its training position. Discrimination training in which food reinforcement is available under one floor tilt condition but not under another steepens the slope of such gradients. In a secondv experiment, pigeons reinforced for pecking when the floor was tilted 10 degrees or 20 degrees and not reinforced under the alternative condition showed steep gradients with maximal responding displaced from the reinforced stimulus.