Michael F. Land

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

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 subjects 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 (eg kettle and lid), and checking the state of some variable (eg 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.

From eye movements to actions: how batsmen hit the ball

In cricket, a batsman watches a fast bowlers ball come toward him at a high and unpredictable speed, bouncing off ground of uncertain hardness. Although he views the trajectory for little more than half a second, he can accurately judge where and when the ball will reach him. Batsmens eye movements monitor the moment when the ball is released, make a predictive saccade to the place where they expect it to hit the ground, wait for it to bounce, and follow its trajectory for 100–200 ms after the bounce. We show how information provided by these fixations may allow precise prediction of the balls timing and placement. Comparing players with different skill levels, we found that a short latency for the first saccade distinguished good from poor batsmen, and that a cricket players eye movement strategy contributes to his skill in the game.

Visual control of flight behaviour in the hoverflySyritta pipiens L.

Summary1.The visually guided flight behaviour of groups of male and femaleSyritta pipiens was filmed at 50 f.p.s. and analysed frame by frame. Sometimes the flies cruise around ignoring each other. At other times males but not females track other flies closely, during which the body axis points accurately towards the leading fly.2.The eyes of males but not females have a forward directed region of enlarged facets where the resolution is 2 to 3 times greater than elsewhere. The inter-ommatidial angle in this “fovea” is 0.6°.3.Targets outside the fovea are fixated by accurately directed, intermittent, open-loop body saccades. Fixation of moving targets within the fovea is maintained by “continuous” tracking in which the angular position of the target on the retina (Θe) is continuously translated into the angular velocity of the tracking fly (

Chasing behaviour of houseflies (Fannia canicularis)

\dot \Phi _p

The Morphology and Optics of Spider Eyes

) with a latency of roughly 20 ms (

Vision, eye movements, and natural behavior.

\dot \Phi _p = k \Theta _e