'Seeing the wood and the trees: experiments on visual texture'
The human visual system is sensitive to both primary cues, such luminance and colour, and secondary cues such as visual texture, motion, and stereoscopic depth. The distinction is that secondary cues must be 'computed' by comparing the 'values' of primary cues across space or time or between the eyes. Although they are derived cues the secondary cues are none the less important for object detection and recognition, and for navigation. This assertion is seldom disputed for depth and motion but has been challenged in the case of visual texture. Some authors argue that this cue is detected only as a by product of other processing and that it provides no information that is not available through other modalities. Using psychophysical and neuropsychological methods, I will argue that our ability to process visual texture is a 'design feature' not an artefact, that it is important for a variety of scene analysis tasks, that texture is processed independently of primary cues at least up to the point of detection, and that texture conveys information not directly available in the primary cues. I will also look at the relationships between various types of visual texture.