Abstract
When a body movement systematically co-occurs with a stimulus, a change in perception to “correct” for this correlation may occur. Sensorimotor adaptation of this kind was demonstrated in an intriguing recent study by Bompas & O'Regan (2006). Our procedure was similar to that of Bompas & O'Regan. In the adaptation phase, which lasted approximately 40 minutes, we induced a correlation between leftward eye saccades and a red stimulus, and rightward eye saccades and a green stimulus. In this adaptation phase, observers performed an incidental task involving judgments of the shapes of the spots. In a subsequent test phase, observers compared the color of two stimuli after leftward and rightward saccades. The major result was that stimuli tended to look greener after a leftward saccade and redder after a rightward saccade, like Bompas & O'Regan's result. This finding is consistent with sensorimotor adaptation. Unlike Bompas and O'Regan, we used a white rather than dark background, and the colored stimuli were approximately equiluminant with that background. Contrasts were measured in cone contrasts to better quantify the magnitude of the effect, rather than using distance in CIE space. The spots we used were smaller than the 10 deg diameter spots of Bompas & O'Regan. We always had a red-green neutral (yellow) stimulus as one of the two spots presented in each trial of the test phases. Using the criteria set forth by Bompas & O'Regan, we obtained sensorimotor adaptation even with stimuli having no luminance contrast with the background. Bompas & O'Regan reported that 9 out of 10 of the observers showed the effect of sensorimotor adaptation, whereas we our effects were weaker. However, we also saw idiosyncratic biases in the initial test phase, before adaptation, that complicate the interpretation of these data.