Biomedical subjects

Mary Hayhoe

Publications and source records attributed to Mary Hayhoe.

4 recordsLinked to original sources

PubMed2006

Look-ahead fixations: anticipatory eye movements in natural tasks.

During performance of natural tasks subjects sometimes fixate objects that are manipulated several seconds later. Such early looks are known as "look-ahead fixations" (Pelz and Canosa in Vision Res 41(25-26):3587-3596, 2001). To date, little is known about their function. To investigate the possible role of these fixations, we measured fixation patterns in a model-building task. Subjects assembled models in two sequences where reaching and grasping were interrupted in one sequence by an additional action. Results show look-ahead fixations prior to 20% of the reaching and grasping movements, occurring on average 3 s before the reach. Their frequency was influenced by task sequence, suggesting that they are purposeful and have a role in task planning. To see if look-aheads influenced the subsequent eye movement during the reach, we measured eye-hand latencies and found they increased by 122 ms following a look-ahead to the target. The initial saccades to the target that accompanied a reach were also more accurate following a look-ahead. These results demonstrate that look-aheads influence subsequent visuo-motor coordination, and imply that visual information on the temporal and spatial structure of the scene was retained across intervening fixations and influenced subsequent movement programming. Additionally, head movements that accompanied look-aheads were significantly smaller in amplitude (by 10 degrees) than those that accompanied reaches to the same locations, supporting previous evidence that head movements play a role in the control of hand movements. This study provides evidence of the anticipatory use of gaze in acquiring information about objects for future manipulation.

Adult↗

PubMed2006

Control of attention and gaze in complex environments.

In natural behavior, fixation patterns are tightly linked to the ongoing task. However, a critical problem for task-driven systems is dealing with unexpected stimuli. We studied the effect of unexpected potential collisions with pedestrians on the distribution of gaze of subjects walking in a virtual environment. Pedestrians on a collision course with the subject were surprisingly ineffective in evoking fixations, especially when subjects were additionally occupied with another task, suggesting that potential collisions do not automatically attract attention. However, prior fixations on pedestrians did increase collision detection performance. Additionally, the detection of potential collisions led to a short-term change in the strategy of looking at subsequent pedestrians. The overall pattern of results is consistent with the hypothesis that subjects typically rely on mechanisms that are initiated top-down to detect unexpected events such as potential collisions. For this to be effective, subjects must learn an appropriate schedule for initiating search through experience with the probabilities of environmental events.

Adult↗

PubMed2005

Eye movements in natural behavior.

The classic experiments of Yarbus over 50 years ago revealed that saccadic eye movements reflect cognitive processes. But it is only recently that three separate advances have greatly expanded our understanding of the intricate role of eye movements in cognitive function. The first is the demonstration of the pervasive role of the task in guiding where and when to fixate. The second has been the recognition of the role of internal reward in guiding eye and body movements, revealed especially in neurophysiological studies. The third important advance has been the theoretical developments in the fields of reinforcement learning and graphic simulation. All of these advances are proving crucial for understanding how behavioral programs control the selection of visual information.

Behavior↗

PubMed2002

Visual short-term memory and motor planning.

Despite extensive experimental work showing that memory for visual information in prior fixations is limited, the nature and content of the information maintained across fixations, when vision functions in its natural context, is not well determined. To gain insight into what memory representations might be needed to support vision in the natural world, we examined eye and hand movements while subjects made a sandwich and while they copied a toy model in a virtual environment. Patterns of eye-hand coordination and fixation sequences suggest the need for planning and coordinating movements over a period of a few seconds. Since the movement plan is initiated when the eye is in a different position from that when the movement itself is made, the planning must be in a coordinate frame that is independent of eye position. Movement planning thus requires a representation of the spatial structure in a scene that is built up over different fixations.

Fixation, Ocular↗