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http://pss.sagepub.com/content/18/3/222 The online version of this article can be found at:
DOI: 10.1111/j.1467-9280.2007.01878.x
2007 18: 222Psychological Science R.S.W. Masters, J. van der Kamp and R.C. Jackson
Imperceptibly Off-Center Goalkeepers Influence Penalty-Kick Direction in Soccer
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Short Report
Imperceptibly Off-Center Goalkeepers Influence Penalty- Kick Direction in Soccer R.S.W. Masters,1 J. van der Kamp,1,2 and R.C. Jackson1
1 Institute of Human Performance, The University of Hong Kong, Hong Kong Special Administrative Region, China, and
2 Faculty of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
The penalty kick generates a variety of strong emotions in soccer
(Carroll, Ebrahim, Tilling, Macleod, & Smith, 2002), and places
the goalkeeper at such a disadvantage that only approximately
18% of penalty kicks are saved (Kropp & Trapp, 1999). We
asked whether a goalkeeper can, by standing marginally left or
right of goal center, bias a penalty taker implicitly to kick to the
side with greater area, thus allowing the goalkeeper to dive in
that direction to make a save. We show that the penalty taker
is unlikely to be mindful that the goalkeeper is off center, but
nevertheless can identify the side with greater area and will be
more likely to direct the penalty kick to that side than to the
other side.
Observation of 200 video clips of penalty kicks, including
those in World Cups, African Nations Cups, European Cham-
pionships, and Union of European Football Association (UEFA)
Champions League matches, indicated that goalkeepers stood
marginally left or right of goal center on 96% of occasions. The
mean displacement of the goalkeeper was 9.95 cm, resulting in a
difference of 2.9% between the areas to the left and right of the
goalkeeper (i.e., 2.9% was the difference between the two areas
expressed as a percentage of total area around the goalkeeper,
Darea/area � 100). There was no association between the po- sition of the goalkeeper and the side to which he dived (94 out of
190 dives were to the side with smaller area), w2(1, N 5 190) 5 0.06, which suggests that the displacement was not a purposeful
strategy. Nevertheless, regardless of the many factors that con-
tribute to kick direction, more kicks were directed to the side on
which there was greater area (103 out of 174), w2(1, N 5 174) 5 3.45, prep 5 .905, j 5 .141. In an experimental study, we asked 51 participants to view
300 slides on a 15.4-in. Samsung wide-screen XGA monitor,
from a distance of approximately 50 cm. In each slide, a filled
block was positioned on the goal line at one of 14 displacements
to the right or left of center (the block and goal were scaled to 3%
of the normal size of the German goalkeeper, Oliver Kahn, and
a soccer goal, respectively). Participants were asked to judge on
which side of the block there was greater area and to indicate the
extent of their confidence in their judgment on a scale from 50%
(low confidence) to 100% (high confidence). At differences in
area as small as 0.5%, participants showed low confidence in
their perceptual judgment, yet indicated the side with the
greater area at above-chance levels, t(50) 5 7.70, prep > .999,
d 5 1.078 (see Fig. 1b).
In a more real-world replication, we replaced the block with
an image of Oliver Kahn (e.g., Fig. 1a) and asked 20 participants
to kick a football from a penalty spot (distance to screen 5 4.8 m)
to the side with the greater area and also to indicate their
confidence that they had selected the correct side. The stimuli
were projected onto a screen and were scaled to 44% of life
size. At differences in area of 0.5% and greater, participants’
accuracy was at above-chance levels, t(19) 5 2.70, prep 5 .959,
d 5 0.604 (see Fig. 1c), but only when the differences were
at least 3.0% did participants show significantly increased
confidence in their perceptual judgments, preps � .999, ds � 0.482.
Our data are compatible with Weber’s law in that the smallest
difference in area at which participants showed reliably above-
chance discrimination was constant (�0.5%) regardless of the scaling of the stimuli (i.e., 3% vs. 44% of life size). The
ability to discriminate differences as small as 0.5% is consistent
with the demonstrated ability to discriminate differences as
small as 0.1 to 0.8% in visual line-bisection tasks (e.g., McCourt
& Olafson, 1997; Porac, Searleman, & Karagiannakis, 2006;
Scarisbrick, Tweedy, & Kuslansky, 1987). Such tasks require
judgments of line length that are comparable with the relative-
area judgments in the present studies.
Address correspondence to Rich Masters, Institute of Human Per- formance, The University of Hong Kong, 111-113 Pokfulam Rd., Hong Kong SAR, China, e-mail: [email protected].
PSYCHOLOGICAL SCIENCE
222 Volume 18—Number 3Copyright r 2007 Association for Psychological Science at Vrije University Library on April 20, 2011pss.sagepub.comDownloaded from
In a third study, we assessed whether penalty direction is
biased even when the kicker is unaware of the goalkeeper’s
displacement. To this end, we presented stimuli identical to
those of the second study (again scaled to 44% of life size)
and instructed participants (N 5 32) to take a penalty kick only
when Kahn was standing in the center of his goal. At differences
in area ranging from 1.6 to 3.0%, participants directed their
penalty kicks to the side with the greater area at above-chance
levels ( preps � .926, ds � 0.378), despite kicking only when they believed that the keeper was in the exact center of the goal
(Fig. 1d). The number of kicks dropped considerably at per-
centages greater than 3.0%, which suggests that participants
were mindful of the fact that the goalkeeper was displaced to the
left or right of center.
In summary, we have shown that it is feasible for a goalkeeper
to influence perceptions of area and consequently the direction
of penalty kicks by standing marginally to one side or another of
the goal center; the goalkeeper can then strategically dive to the
side with greater area. Extrapolation of our data indicates that
the optimum displacement of the goalkeeper in real life is from
6 to 10 cm. The penalty taker is unlikely to be mindful of a
displacement in this range, but is at least 10% more likely to
direct the penalty kick to the side with greater area than to the
side with smaller area.
REFERENCES
Carroll, D., Ebrahim, S., Tilling, K., Macleod, J., & Smith, G.D. (2002).
Admissions for myocardial infarction and World Cup football:
Database survey. British Journal of Medicine, 325, 1439–1442. Kropp, M., & Trapp, A. (1999). 35 Jahre Bundesliga-Elfmeter. Kassel,
Germany: Agon Sportverlag.
McCourt, M.E., & Olafson, C. (1997). Cognitive and perceptual influ-
ences on visual line bisection: Psychophysical and chronometric
analyses of pseudoneglect. Neuropsychologia, 35, 369–380. Porac, C., Searleman, A., & Karagiannakis, K. (2006). Pseudoneglect:
Evidence for both perceptual and attentional factors. Brain and Cognition, 61, 305–311.
Scarisbrick, D.J., Tweedy, J.R., & Kuslansky, G. (1987). Hand pref-
erence and performance effects on line bisection. Neuropsy- chologia, 25, 695–699.
(RECEIVED 5/17/06; REVISION ACCEPTED 9/21/06; FINAL MATERIALS RECEIVED 10/2/06)
Fig. 1. Influence of the goalkeeper’s position (displacement from center) on perception and direction of penalties in soccer. An example of a stimulus display used in Studies 2 and 3 is shown in (a); in this particular display, there is proportionally more area (2.2%) on the right side of the goalkeeper than on the left. The graphs in (b) and (c) show results from the first two studies: participants’ accuracy in choosing (Study 1) or di- recting a kick toward (Study 2) the side with greater area and partici- pants’ mean confidence in their judgment, normalized to the difference between the lowest and highest levels of confidence. The graph in (d) presents results from the third study, in which participants kicked only if they believed that the goalkeeper was in the center. The graph shows the percentage of kicks directed to the side with greater area (open circles) and the percentage of trials on which participants took a kick (black squares). All results are graphed as a function of the difference between the areas on the left and right sides of the goalkeeper, expressed as a percentage of total area around the goalkeeper, Darea/area � 100. Error bars indicate standard errors.
Volume 18—Number 3 223
R.S.W. Masters, J. van der Kamp, and R.C. Jackson
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