Generalization of cue recruitment to non-moving stimuli: location and surface-texture contingent biases for 3-D shape perception.

Long-lasting perceptual biases can be acquired through training in cue recruitment experiments (e.g. Backus, 2011; Haijiang et al., 2006). Stimuli in previous studies contained motion, so the learning could be explained as an idiosyncrasy in some specific neuronal population such as the middle temporal (MT) area (Harrison & Backus, 2010a). The current study addresses the generality of cue recruitment by testing whether motion is necessary for learning a cue-contingent perceptual bias. We tested whether location and a novel cue, surface texture, would be recruited as cues to disambiguate perceptually bistable stationary 3-D shapes. In Experiment 1, stereo and luminance cues were used to disambiguate shape according to location in the visual field, and observers' (N=10) percepts on ambiguous test trials became biased in favor of the contingency during training. This bias lasted into the following day. This result together with previous studies that used moving stimuli suggests that location-contingent biases are easily learned by the visual system. In Experiment 2, location was fixed, and instead the new cue to be recruited was a surface texture. Learning did not occur when stimuli were para-foveal, texture was task-irrelevant, and disparity was continuously present in training stimuli (N=10). However, learning did occur when stimuli were central, task was texture-relevant, and disparity was transient (N=8). Thus, we show for the first time that an abstract cue, surface texture, can also be learned without motion.