Abstract
Three pigeons were trained in an upright conditioning chamber to peck a key transilluminated by a vertical line. This training was followed by a line orientation generalization test. During the test, the chamber was tilted laterally 22.5 degrees from upright. The chamber floor remained horizontal with respect to gravity. Under these conditions, the subjects responded more often in the presence of a visually vertical (parallel to chamber walls) line orientation than in the presence of a gravitationally vertical line orientation. Subsequent reinforcement of pecking in the presence of a line that was always gravitationally vertical but not always visually vertical temporarily abolished this "visual field dependency" and resulted in generalization gradients with peak responding in the presence of the gravitationally vertical line orientation. The results are discussed in terms of selective attention to the gravitational and visual components of line orientation.