Spatial Regularities

We frequently search for objects during our everyday lives, and the context we find ourselves in helps predict where the object we are searching for will be located. We have investigated what information we extract and remember as we perform visual search tasks, particularly what we learn by performing a search over and over again in the same context (contextual cueing), and what we learn as we perform a particular search (rapid resumption). Our work has shown that our learning in both of these cases is restricted by computational feasibility, preventing us from using remembering and using all of the available information, yet still being sensitive to the regularities present in the displays.

Categorical Regularities

Growing evidence suggests people are sensitive to subtle statistical regularities in the world, but most of the regularities that have been explored are perceptual in nature. For example, people can easily learn what novel shapes or syllables appear together in a stream even without being consciously aware that they are learning. However, the world containts many high-level, conceptual regularities as well. For example, if I leave my office and enter another room, the chance that the new room is a zoo is nearly zero, whereas the chance that it is a corridor is extremely high. Our work has shown that statistical learning can occur at the categorical level as well. Learning at this level probably helps us compress the amount of information we need to store, since any regularity we learn applies to many possible exemplars.

Memory Capacity

We have investigated the capacity of both short-term memory and long-term memory for visual information. In particular, we have suggested that long-term memory can not only store thousands of objects, but also can store those objects with a remarkable amount of visual detail. We have also attempted to establish the limits of visual working memory in terms of bits rather than 'magical numbers' or chunks, as is traditionally done, using information theoretic measures.

Perceptual organization across spatial scales

Visual perception and recognition are problems of induction - problems where we are given ambiguous input and must decide which of many possible interpretations to take. In middle-level vision, this is typically referred to as the problem of perceptual organization: how we take the bits and pieces of visual information that are available in the retinal image and structure them into larger units like objects. We have investigated perceptual organization across different spatial frequencies - how the blurry, low spatial frequency of an image and the fine, high spatial frequency details in that image interact to form our eventual percept. Our visual system is thought to break down images by spatial frequency early on in the visual pathway, so examining perceptual organization across spatial frequencies allows us to get a better idea of the types of integration the visual system has to deal with as it builds a representation of the world. We have concluded that assymmetric hysteresis effects allow our visual system to integrate across spatial frequencies in a way that provides us with the most accurate interpretation of the world as we move through it.