DATA SET 6: Mike Land's Cricket Playing Data Set

Description
The sequence here shows a batsman, wearing an eye camera, receiving a medium pace (ca. 60 mph) ball from a bowling machine (top left, Fig 1). The first clip simply shows the delivery, in real time. The second the same delivery with the eye direction added as a 1º white dot (the ball is the small black dot). These two clips are then repeated. The next two clips are the same delivery, but slowed down by a factor of about 5, so that the anticipatory gaze change can be easily observed. As Fig 1 shows, gaze reaches the future bounce point nearly 100 ms ahead of the ball itself.

By knowing the time from delivery to bounce, and the declination angle of the bounce point, a batsman can determine when the ball will reach the bat, and the height it will be at that time. This information will allow him to produce an accurate, well-timed stroke. The key to this is an early, reasonably accurate, anticipatory saccade. We found that good players have a latency of only about 130 ms for such saccades, but weaker players may be up to 100 ms later.

Fig 1: Upper part: The batsman’s view of the ball leaving a bowling machine. (1) Ball about to emerge, batsman’s gaze (white dot, 1º across) watching the aperture. (2) Ball (small black dot) descending from the aperture with gaze starting to follow. (3) Gaze saccade to a spot close to the bounce point, which the ball will not reach for a further 0.1 s. Object in centre of each frame is a camera tripod. Lower part, main graph. Vertical direction of gaze (●) and ball (○) viewed from the batsman’s head. Numbers correspond to photographs above. Note that the saccade after 2 brings gaze close to the bounce point. After the bounce gaze tracks the ball until about 0.6 s after delivery. The ball is struck at 0.7 s. Upper graph: difference between gaze and eye direction. Note that the batsman must take his eye off the ball by about 51 in order to anticipate the bounce.

Method
Eye movement recordings were made with a head-mounted camera that produced a split image in which the top two-thirds showed the scene ahead and the lower third the eye in its socket, imaged via a concave mirror. The location and ellipticity of the iris were used to obtain the coordinates of eye direction, by matching the iris outline to a computer- generated eye model. This was done by hand, frame-by-frame, at 50 f.p.s. The coordinates were used to position a 1º dot on the upper scene view, and each frame re-recorded. Head movements could also be obtained by tracking distant background objects in the scene view. The resulting video contains numerical values (in degrees) of the direction of view of the fovea, a frame counter, and a clock. The videos are reversed left to right as a result of the mirror optical system.

Reference
Land MF, McLeod P (2000) From eye movements to actions: how batsmen hit the ball. Nature Neuroscience 3: 1340-1345

SCENE/DISPLAY/STIMULI IMAGES/VIDEOS

SCANPATH (EYE-TRACKER) DATA

Cricket Playing Preview (2361 KB, DIVX compression)

Cricket Playing Full Data Set (uncompressed avi, zipped: 22219 KB)