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Research Quarterly for Exercise and Sport
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Gaze Behavior in Basketball Shooting
a b b
Rita F. de Oliveira , Raôul R. D. Oudejans & Peter J. Beek
a
Institute of Psychology , German Sport University
b
Research Institute MOVE , VU University Amsterdam
Published online: 23 Jan 2013.
To cite this article: Rita F. de Oliveira , Raôul R. D. Oudejans & Peter J. Beek (2008) Gaze Behavior in Basketball Shooting, Research
Quarterly for Exercise and Sport, 79:3, 399-404, DOI: 10.1080/02701367.2008.10599504
To link to this article: http://dx.doi.org/10.1080/02701367.2008.10599504
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conditionsde Oliveira,
Research Note—Motor Oudejans,
Control and Beek
and Learning
Research Quarterly for Exercise and Sport
©2008 by the American Alliance for Health,
Physical Education, Recreation and Dance
Vol. 79, No. 3, pp. 399–404
Gaze Behavior in Basketball Shooting: Further Evidence
for Online Visual Control
Rita F. de Oliveira, Raôul R. D. Oudejans, and Peter J. Beek
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Key words: expert performance, far aiming, free throw, Subsequent research has challenged the notion
jump shot that successful basketball shooting always involves, or
should involve, extensive movement preprogramming.
T he role of gaze behavior in sports has been examined
extensively to identify visual search strategies and dif-
ferences therein between skilled and less skilled athletes
It became apparent that if the target was visible until
ball release, seeing it for only the last 397 ms was suf-
ficient for successful jump shooting (Oudejans, van de
(e.g., Williams, Davids, & Williams, 1999). An important Langenberg, & Hutter, 2002). Using an occlusion para-
finding is that experts look longer at relevant areas than digm, these authors found that shooters performed well
nonexperts (e.g., Janelle et al., 2000; Vickers, 1996; Wil- when only late viewing was allowed but performed poorly
liams, Singer, & Frehlich, 2002). For example, Vickers when ample early viewing was allowed. In this context, it
used an eye-tracking system to record the gaze behavior is important to realize that arm kinematics in basketball
of expert and near expert shooters during preparation shooting determines whether or not the basket is visible
of the free throw. Target fixation durations showed that during the last elbow extension. If the propulsion hand
expert shooters looked at the target area more than remains below the line of sight, the hands and ball oc-
twice as long as near experts (972 vs. 357 ms). Vickers clude the target as soon as the elbow starts to extend.
interpreted this finding to imply that long durations of The participants in the Vickers (1996) study used this low
visual fixation are necessary to allow detailed param- (hand) shooting style. If the propulsion hand and ball
eterization for the required shooting movements. This rise above the line of sight before elbow extension, the
is in accordance with other authors who deemed this target is visible during the entire elbow extension until
period of fixation to be essential for programming the ball release. Participants in the Oudejans et al. (2002)
movement direction, force, and velocity, as well as limb study used the high (hand) shooting style. Thus, whether
coordination and timing (Williams, Singer, & Frehlich, or not players can see the target after the ball and hands
2002). In addition, Vickers found that expert shooters enter the line of sight (mLoS = moment of line of sight)
suppressed their vision of the target, either by blinking will determine their shooting style. So defined, shooting
or looking away, as they initiated the final shooting move- style is an observable characteristic that is preserved in
ment of the free throw. In line with the notion that far the presence of opponents and in shooting distances
aiming movements are controlled in open-loop fashion, within (at least) the 3-point line (Elliott, 1992; Miller &
she interpreted this finding as a strategy to reduce inter- Bartlett, 1993; Rojas, Cepero, Oña, & Gutierrez, 2000).
ference between the visual and motor systems. Furthermore, using an intermittent viewing para-
digm, de Oliveira, Oudejans, and Beek (2006) found
that a late pick up of visual information in both low- and
Submitted: January 1, 2007 high-style shooters characterizes expert performance of
Accepted: September 5, 2007 the jump shot. In their study, long fixations were denied
by virtue of intermittent occlusions, but gaze behavior
Rita F. de Oliveira is with the Institute of Psychology at the
German Sport University. Cologne Raôul R. D. Oudejans was not recorded. In a subsequent study, de Oliveira,
and Peter J. Beek are with the Research Institute MOVE Huys, Oudejans, van de Langenberg, and Beek (2007)
at VU University Amsterdam. found that basketball jump shot performance deterio-
RQES: September 2008 399
de Oliveira.indd 399 8/19/2008 5:01:06 PMde Oliveira, Oudejans, and Beek
rated when visual information was unavailable during previous findings, we hypothesized that low-style shoot-
movement execution. When vision was occluded just ers would look at the target relatively long before their
before initiating the shooting movement, there were hands and ball occlude the target in the free throw but
marked decrements in performance as well as clear de- for a shorter duration in the jump shot. In addition, we
creases in interjoint coordination strength and stability. hypothesized that high-style shooters would look at the
Collectively, these findings underscored the importance target during the final elbow extension both in the free
of the online use of visual information in basketball throw and the jump shot.
shooting. However, there are three important caveats
of those studies vis-à-vis the Vickers (1996) study, which,
as it stands, preclude regarding the aforementioned
conclusion as final or general. Method
The first concerns the methods used. While Vickers
(1996) used an eye tracking system to study the duration
Participants
and location of gaze behavior, subsequent studies (de
Oliveira et al., 2006, 2007; Oudejans et al., 2002) used Six experienced basketball players participated in
visual occlusion methods to study the timing of optical the experiment (4 men and 2 women, M age = 27.7
information pickup. Whereas gaze behavior informs years, SD = 7.9). All played in the two highest basketball
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about locations of interest in the environment, it does leagues in The Netherlands for 11 years on average (SD
not inform about the relevance of visual information = 6.4). Three participants exhibited a high shooting
at different movement moments. Conversely, whereas style (all men) and 3 a low shooting style (1 man and
occlusion methods inform about the sufficient and nec- 2 women), which was confirmed by video footage after
essary timing of visual information pick-up, they do not the experiment (cf., de Oliveira et al., 2006). The ethics
inform about what locations are actually fixated. Because committee of the Faculty of Human Movement Sciences
previous conclusions pertained to different methodolo- approved the experiment. Each participant provided
gies, it is difficult to evaluate their relative merits and written informed consent before the experiment.
validity, especially with regard to high-style shooters. To
date, their gaze behavior has not been examined.
Apparatus
The second caveat concerns the shot type (i.e., free
throw vs. jump shot). Vickers’ (1996) results pertained We placed a standard basketball backboard and
to the free throw, in which the relative positions of target rim in a laboratory and marked a line on the floor 4.6
and performer are unchanged during the movement. m from the backboard, which is the official distance for
Subsequent results pertained to the jump shot, a dy- taking free throws. Gaze behavior was registered using
namic task involving a whole body movement in which an eye tracking system (Applied Science Laboratories
the relative positions between player and target change 501, Bedford, MA) that consisted of a head-mounted
continuously. Although it is unlikely that different shot scene camera (50 Hz) and a monocular corneal reflec-
types would require different patterns of visual control, tion system. In brief, the system recorded the field of
this has never been verified before. view with a superimposed marker that corresponded
The third caveat is the possible influence of the ki- to gaze direction. A digital video camera (50 Hz) was
nematic pattern of high- and low-style shooters on visual placed orthogonal to the shooting plane to determine
information in basketball shooting. The kinematics of the moment of ball release (cf., de Oliveira et al., 2006).
high-style shooters allow the target to be visible until ball Two light emitting diodes (LEDs), one at the left and one
release, permitting visual information to be picked up in front of the participant, signaled each trial initiation.
and used online, that is, during the shot. In contrast, Official FIBA regulation-size basketballs were used.
low-style shooters occlude the target with their hands
during the final elbow extension, lending support to
Procedure
the interpretation of open-loop control, in which visual
information is picked up only before movement initia- After a brief explanation of the task, participants
tion (Vickers, 1996; cf. Oudejans et al., 2002). took several warm-up shots, before and after the eye
The goal of the present study was to resolve the tracking system was mounted, adjusted, and calibrated.
current ambiguity in and inconclusiveness of the under- They were instructed to look at the LED below the
standing of the visual control in basketball shooting by backboard and start the trial when the LED switched on.
accounting for all three factors. Specifically, we examined This allowed the experimenter to verify the eye tracking
the gaze behavior of 6 expert basketball players, 3 with a system calibration on each trial. Participants performed
high and 3 with a low shooting style, while they prepared 10 free throws and 10 jump shots in blocked fashion. The
and performed free throws and jump shots. Based on order of block execution was counterbalanced across
400 RQES: September 2008
de Oliveira.indd 400 8/19/2008 5:01:06 PMde Oliveira, Oudejans, and Beek
participants. The free throw consisted of shooting from ing the final elbow extension, whereas in all high-style
the line within the official 5 s. The jump shot consisted players the target remained visible after the ball passed
of taking a step and a dribble, then stopping and jump their line of sight until ball release. Two researchers
shooting from the line in a continuous self-paced move- independently repeated the procedure with 100% agree-
ment. Finally, the eye-tracking system was removed and ment. This analysis confirmed that 3 participants had a
participants took another 10 free throws and 10 jump low shooting style and 3 had a high shooting style.
shots to establish their percentage of hits for undisturbed
shooting. Each trial was registered as a hit or miss. Indi-
Looking Behavior
vidual testing lasted about 45 min.
The total duration of looking behavior was indepen-
dent of shot type and style group. A significant effect of
Data Reduction
period, F(1, 4) = 9.08, p = .039, H2 = .69, revealed that par-
Looking behavior was coded for each frame starting ticipants looked longer at the target before mLoS than
with LED illumination and ending with ball release. The after. There was also a significant Period × Style Group
scores ranged from 0 to 1 such that looking at the rim was interaction, F(1, 4) = 10.66, p = .031, H2 = .73. This effect
1, the basket’s net or the small square on the backboard occurred because participants in the low-style group
was .8, the remaining backboard was .6, other locations looked at the target significantly longer before mLoS
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were .4, and no gaze behavior was 0. We registered the than after, T(N = 6) = 2.21, p = .03, whereas there was no
moment when the ball entered the participants’ field such difference in the high-style group, T(N = 6) = 0.27,
of view (further denoted mLoS, the moment of passing p = .79. Complementary pairwise comparisons showed
the line of sight) and the duration of target occlusion. that looking before mLoS was significantly longer in the
For each condition, we calculated the average duration low-style than in the high-style group, T(N = 12) = 2.09,
of looking behavior directed at the target (i.e., basket p = .04, whereas, conversely, looking after mLoS was
or backboard, scores q .6) and submitted those average significantly longer in the high-style than the low-style
durations to a repeated measures 2 x 2 x 2 analysis of group, T(N = 12) = 2.95, p < .01 (see Figure 1).
variance (ANOVA) with shot type (2 levels: free throw,
jump shot) and period (2 levels: before, after mLoS) as
within-participant factors and style group (2 levels: low,
high style) as between-participants factor. Five partici-
pants started looking at the target less than 1.2 s before
mLoS; therefore, we depicted this period in Figure 2. In
addition, we calculated the duration of target occlusion
(i.e., the duration of mLoS) and the final period (i.e.,
from start of mLoS to ball release) and submitted those
durations to repeated measures 2 x 2 ANOVAs with
shot type as within-participants factor and style group as
between-participants factor. The percentage of hits was
submitted to (nonparametric) Wilcoxon Signed Ranks
Tests. Significance for each analysis was set at p < .05.
Results
Shooting Style
To verify participants’ shooting styles, we analyzed
images from the cameras. Footage from the side view
camera showed whether or not participants brought the Figure 1. Average duration of looking behavior for each style
group and shot type. Triangles pointing left indicate average
ball above the head before the final elbow extension,
durations before the ball and hands passed the players’ line
displaying a high or low shooting style. Previously, this
of sight (mLoS); triangles pointing right indicate durations
method was used to assess shooting style and corrobo- after mLoS. Bars represent 2 standard errors (SE) of the
rated more elaborate methods (cf., de Oliveira et al., mean. The third bar replicates the result found by Vickers (M
2006). In addition, footage of the head-mounted camera = 1,213 ms, SE = 351), while the sixth replicates the result
showed that all low-style players occluded the target dur- found by Oudejans et al. (M = 360 ms, SE = 25).
RQES: September 2008 401
de Oliveira.indd 401 8/19/2008 5:01:07 PMde Oliveira, Oudejans, and Beek
Figure 2 depicts the individual pattern of looking of style but significantly longer for the free throw than
behavior during each trial for each shot type. As sug- for the jump shot, F(1, 4) = 9.90, p < .05, H2 = .71. Finally,
gested by the figure, the final period duration was longer the percentage of hits (overall 68%, SD = 15) was inde-
in the high-style than the low-style group, F(1, 4) = 6.97, p pendent of shooting style group, shot type, and the use
= .058, H2 = .64, independent of shot type. Furthermore, of the eye-tracking system, all T(2 or 4) < 2.24, p > .08.
the duration of target occlusion immediately following The percentages of hits for each participant and each
mLoS (depicted as a gap in each plot) was independent shot type are also reported in Figure 2.
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Figure 2. Each participant’s looking behavior pattern and shot type (jump shot and free throw) for each trial. Accumulated
scores greater than .6 indicate the participant was looking at the target area. A gap indicates the average duration of the line of
sight (mLoS) for each participant and condition. For representational purposes, mLoS = 0 s. Filled circles indicate the moment
of ball release for each trial. Corresponding shooting percentages are indicated in the upper right corner of each panel.
402 RQES: September 2008
de Oliveira.indd 402 8/19/2008 5:01:07 PMde Oliveira, Oudejans, and Beek
Discussion associated with about 400 ms of vision after mLoS and
practically no vision before mLoS (see Figure 2).
The aim of the present study was to help resolve In combination with previous results (de Oliveira
conflicting findings and interpretations regarding the et al., 2006, 2007; Oudejans et al., 2002), the present
visual control of basketball shooting by examining the findings corroborate the view that basketball shooting
looking behavior of 6 expert basketball players (3 with is largely controlled online by vision, in the sense that
a low shooting style and 3 with a high shooting style) visual information is picked up and used during move-
executing both free throws and jump shots. As hypoth- ment execution. The specifics of the timing of optical
esized, the expert low-style shooters looked compara- information pick-up depend on both the prevailing
tively long at the target area when taking free throws, shot type and shooting style. These findings derive their
as was the case in previous research (Vickers, 1996). relevance from the failure in previous studies to account
However, this does not imply that low-style shooters for the confounding influence of shooting style, which
used this long fixation duration to preprogram their resulted in ill-grounded conclusions.
movements. Although several authors have assumed that Despite the improved understanding of visual con-
long visual fixations are necessary for preprogramming trol in basketball shooting achieved here, it is unknown
various movement parameters, like direction, force, ve- what information expert players use as they organize and
locity, timing, and limb coordination (cf., Williams et al., deliver a basketball shot. To date, research has focused
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2002), they have said little about the nature and details predominantly on retinal sources of information by
of preprogramming. Nevertheless, it has been argued investigating either gaze behavior or consequences of
that long target fixations may enhance performance, visual occlusion. A notable exception is the Ripoll, Bard,
because performers would use this time for psychologi- and Paillard (1986) study of head and eye stabilization
cal and physiological regulation (Williams et al., 2002). in basketball shooting, which showed that head stabiliza-
Moreover, contrary to what Vickers reported, none of tion is a reference for subsequent movement. In other
the participants blinked or looked away from the target tasks, kinesthetic information about the orientation
at movement initiation. Instead, the participants contin- and movements of head and eyes has also been found
ued fixating the target either until the hands and ball to play a prominent role (e.g., Ooi, Wu, & He, 2001;
occluded the target or until ball release, depending on Oudejans, Michaels, Bakker, & Davids, 1999). Besides
their shooting style (see Figure 2). these variables, it has been suggested that relatively in-
With the more dynamic shot task (i.e., the jump variant factors, such as eye level or the official height of
shot), we found that low-style shooters looked at the the basket, are used in basketball shooting (de Oliveira,
target only half as long (1 vs. 0.5 s) as in the free shot with- Oudejans, & Beek, in press; Oudejans, Koedijker, Blei-
out any consequence for their shooting performance. jendaal, & Bakker, 2005). Therefore, investigating the
This finding is consistent with previous evidence for informational basis of basketball shooting is an exciting
the informative value of the last moments before mLoS and rich avenue for future research on the coupling of
(de Oliveira et al., 2006) as well as with the finding that perception and action in far aiming tasks.
viewing the target for 3 s prior to movement initiation
was insufficient for accurate performance if no vision was
allowed during the movement (de Oliveira et al., 2007).
In this context, the argument that low-style shooters must References
preprogram their movements due to the target occlu- de Oliveira, R. F., Huys, R., Oudejans, R. R. D., van de Langen-
sion following mLoS is invalid. Because the duration of berg, R., & Beek, P. J. (2007). Basketball jump shooting
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the literature, low-style shooters may have used updated 180–186.
optical information at the moment of ball release. de Oliveira, R. F., Oudejans, R. R. D., & Beek, P. J. (2006).
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at the target during the final shooting movements. This shooting. Journal of Sports Sciences, 24, 933–940.
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At the time of this study, the first author was with the
Oudejans, R. R. D., van de Langenberg, R. W., & Hutter, R. Faculty of Human Sciences at VU University Amsterdam.
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I. (2002). Aiming at a far target under different viewing Please address all correspondence concerning this
conditions: Visual control in basketball jump shooting. article to Rita Ferraz de Oliveira, German Sport Uni-
Human Movement Science, 21, 457–480. versity Cologne, Institute of Psychology, Am Sportpark
Ripoll, H., Bard, C., & Paillard, J. (1986). Stabilization of head Müngersdorf 6, Cologne, Germany 50933.
and eyes on target as a factor in successful basketball
shooting. Human Movement Science, 5, 47–58. E-mail: r.oliveira@dshs-koeln.de
404 RQES: September 2008
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