Look-ahead fixations: anticipatory eye movements in natural tasks

Abstract

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.

Eye movements during natural actions in patients with schizophrenia

“…Hayhoe and colleagues 19 and Land and colleagues 21 have observed that about one-third of reaching and grasping movements were preceded a few seconds earlier by a fixation on the object. In a similar construction task, Mennie and colleagues 27 reported a 20% rate of look-aheads, a value similar to that found in our study. Thus, patients seem to establish a less efficient planning strategy than controls.…”

“…Look-ahead fixations occur on average 3 seconds before the reach, and their frequency is influenced by task sequence, suggesting that they are purposeful and are thought to reflect planning of the next action. 27 A 2 (group: patients/controls) × 2 (task: familiar/unfamiliar) repeated-measures multivariate ANOVA showed a significant main effect of group (F 1,28 = 6.9, p = 0.013, ηp 2 = 0.20) and task (F 1,28 = 12.1, p = 0.002, ηp 2 = 0.30) on the percentage of lookahead fixations. There was also a significant interaction between group and task (F 1,28 = 4.4, p = 0.044, ηp 2 = 0.14).…”

Evidence for a distributed hierarchy of action representation in the brain

“…An interesting symmetry emerges in these models: Prediction turns motor commands into expected sensory consequences, whereas control turns desired consequences into motor commands. Prediction is readily observed in prehension tasks, where the eyes lead the hand in locating goal targets Mennie, Hayhoe, & Sullivan, 2006). It has been shown in learning studies that prediction emerges faster than control (Flanagan, Vetter, Johansson, & Wolpert, 2003).…”

Vision and the representation of the surroundings in spatial memory

“…When washing one's hands [58] or making a sandwich [59], fixations are occasionally made to objects that are not involved in the current part of the task but will be the focus of an upcoming act. These 'look-ahead' fixations may occur several seconds before that object is used but have a measurable benefit for the efficiency with which the target is later re-acquired [60].…”

“…First, and as described here, we may rely more upon remembered information from our allocentric map when constructing the egocentric map. Second, we may vary the reliance upon immediate retinocentric visual information and the egocentric map depending upon the reliability and availability of visual information [60]. Within the visual field itself, the balance between information from vision and memory is likely to vary with eccentricity, with vision dominating in the region around the fovea and being increasingly supplemented by egocentric memory towards the periphery.…”