The Roles of Vision and Eye Movements in the Control of Activities of Daily Living

Abstract

The aim of this study was to determine the pattern of fixations during the performance of a well-learned task in a natural setting (making tea), and to classify the types of monitoring action that the eyes perform. We used a head-mounted eye-movement video camera, which provided a continuous view of the scene ahead, with a dot indicating foveal direction with an accuracy of about 1 deg. A second video camera recorded the subject's activities from across the room. The videos were linked and analysed frame by frame. Foveal direction was always close to the object being manipulated, and very few fixations were irrelevant to the task. The first object-related fixation typically led the first indication of manipulation by 0.56 s, and vision moved to the next object about 0.61 s before manipulation of the previous object was complete. Each object-related act that did not involve a waiting period lasted an average of 3.3 s and involved about 7 fixations. Roughly a third of all fixations on objects could be definitely identified with one of four monitoring functions: locating objects used later in the process, directing the hand or object in the hand to a new location, guiding the approach of one object to another (e.g. kettle and lid), and checking the state of some variable (e.g. water level). We conclude that although the actions of tea-making are 'automated' and proceed with little conscious involvement, the eyes closely monitor every step of the process. This type of unconscious attention must be a common phenomenon in everyday life.

Sources of variability in interceptive movements

“…Here again all 1058 trials without missing data are included. When performing everyday tasks our eyes are usually directed at the object or objects that are relevant for what we are doing at that moment Johansson et al 2001;Land et al 1999;Land and Hayhoe 2001;Triesch et al 2003), or toward positions at which critical information is expected to become available (e.g., information about how a ball bounces; Land and Furneaux 1997;Land and McLeod 2000). We could therefore tentatively conclude from Fig.…”

Learning robotic eye–arm–hand coordination from human demonstration: a coupled dynamical systems approach

“…In spite of the predominance of brief durations of fixations in prehension movements, it has been shown that they do support movement control. Several studies have shown that visual information necessary for movement control can be computed within a single fixation (Ballard et al 1995;Land et al 1999). This indicates quite efficient visual processing of some easy-tocompute visual features required for online arm movement control.…”

“…For the remaining 91.7 % of the task, gaze and arm movements are synchronously driven to the same goal (to the obstacle during the first segment of movement, and toward the target after the obstacle is passed). Land et al (1999) observed in their teamaking experiment that the gaze and arm movements are highly coupled during execution of each subtask, but when it comes to a transition toward a new target, the gaze switches approximately 0.5 s before the movement of the arm to the previous object is completed. Johansson et al (2001) found that the difference between the gaze exit times and arm exit times was quite tight when executing sequential tasks, but the gaze starts moving toward the new target slightly before the hand does (∼100-200 ms), as well.…”

“…It also enables to react rapidly in the face of a sudden perturbation, such as an obstacle entering the workspace (Aivar et al 2008). There is a tight coupling between visual and motor modalities when driving prehensile motion (Prablanc et al 1979;Land et al 1999;Johansson et al 2001). While this coupling has been documented at length in the literature in free space motion (Johansson et al 2001;Hayhoe et al 2003;Bowman et al 2009), little is known about how this coupling is exploited to enable fast and reliable obstacle avoidance, and in particular when the obstacle appears after the onset of motion.…”

The relative timing between eye and hand in rapid sequential pointing is affected by time pressure, but not by advance knowledge

“…During relatively slow sequences [e.g. making tea; see Land and Hayhoe (2001) for review], gaze typically lands on the target on average 560 ms prior to any hand movement, thus providing sufficient time to process and combine retinal and extra-retinal information for movement planning (Land et al 1999). However, in more temporally demanding sequence tasks such as typing a text message on a mobile phone or picking up and moving objects on a fastmoving production line, the visuo-motor system would be challenged by feedback delays (up to 165 ms for visual processing; e.g.…”