image of the eye. The relative position of these features is used to compute the visual
point of gaze. The infra-red eye camera records displacement data from the left or right
pupil and cornea.
Using such eye-tracking systems, a considerable amount of research has been
conducted on the eye movements of athletes in recent years. Typical stimuli used in these
studies include static slides depicting schematic sport situations as well as dynamic video
presentations of similar material (see review by A.M.Williams et al., 1999). Certain
inferences are drawn from the location and duration of the perceiver’s visual fixations.
For example, the location of a fixation is usually regarded as an index of the relative
importance of a given cue within a stimulus display. In addition, the number and duration
of fixations recorded (which define “search rate”) are believed to reflect the information-
processing demands placed on the perceiver. Using such variables, expert-novice
differences in visual search strategies have been discovered in such sports as soccer
(Helsen and Starkes, 1999), tennis (Singer, Cauragh, Chen, Steinberg and Frehlich,
1996), boxing (Ripoll, Kerlirzin, Stein and Reine, 1993), golf (Vickers, 1992) and
basketball (Vickers, 1996).
A prediction that is frequently tested in this field is that expert athletes will display a
more efficient visual search strategy than relatively less skilled counterparts when
inspecting sport-specific displays. This means that they will show fewer visual fixations
of longer length—and focus more on “information rich” areas of the display than will
relative novices. To find out if this prediction is supported in cricket, see Box 6.3.
Box 6.3 Expert-novice differences in the eye movements of cricket
batsmenCricket is an exciting and skilful sport in which batsmen face the task of striking balls
bowled to them at fast speeds with uncertain spins and bounces. This task is made all the
more difficult by the fact that cricket balls travel in an arc, change speed when they
bounce and rarely arrive at the eye-level of the batsman. Despite such difficulties, expert
batsmen can judge the arrival time of the ball surprisingly precisely. How is this
remarkable perceptual feat achieved? Recent research by Land and McLeod (2000) tried
to answer this question using eye-tracking technology. Briefly, these authors measured
the eye movements of three expert batsmen as they faced balls bowled at them at speeds
of 25 metres per second, Results showed that in accordance with previous studies, the
cricketers did not keep their eyes continuously on the ball throughout its flight Instead,
they fixated on its initial delivery, made predictive saccades to the place where they
expected it to bounce, waited for it to hit the ground and then tracked its trajectory for up
to 200 milliseconds after the bounce. In other words, they used their cricket knowledge
and experience to make predictions about
the likely destination of the ball before preparing to execute an attacking or defensive
stroke. Interestingly, the expert batsmen were distinguished from their less competent
players by the speed and accuracy of anticipatory saccades. In other words, they saw the
ball early. To summarise, the skill of batting in cricket seems to He as much in the head
as in the hands.
What lies beneath the surface? Investigating expertise in sport 167