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NATURE|Vol 435 | 19 May 2005
293
Red enhances human performance in contests
Signals biologically attributed to red coloration in males may operate in the arena of combat sports.
Red coloration is a sexually selected, testos-
terone-dependent signal of male quality in a
variety of animals
1–5
, and in some non-human
species a male’s dominance can be experimen-
tally increased by attaching artificial red
stimuli
6
. Here we show that a similar effect can
influence the outcome of physical contests in
humans — across a range of sports, we find
that wearing red is consistently associated with
a higher probability of winning. These results
indicate not only that sexual selection may
have influenced the evolution of human
response to colours, but also that the colour of
sportswear needs to be taken into account to
ensure a level playing field in sport.
Although other colours are also present in
animal displays, it is specifically the presence
and intensity of red coloration that correlates
with male dominance and testosterone
levels
3–5
. In humans, anger is associated with a
reddening of the skin due to increased blood
flow
7,8
, whereas fear is associated with
increased pallor in similarly threatening situa-
tions
9
. Hence, increased redness during
aggressive interactions may reflect relative
dominance. Because artificial stimuli can
exploit innate responses to natural stimuli
6,10
,
we tested whether wearing red might
influence the outcome of physical contests
in humans.
In the 2004 Olympic Games, contestants in
four combat sports (boxing, tae kwon do,
Greco–Roman wrestling and freestyle
wrestling) were randomly assigned red or blue
outfits (or body protectors). If colour has no
effect on the outcome of contests, the number
of winners wearing red should be statistically
indistinguishable from the number of winners
wearing blue. However, we found that for
all four competitions, there is a consistent
and statistically significant pattern in which
contestants wearing red win more fights
(
2
4.19, d.f.1, P0.041; Fig. 1a). This
result is remarkably consistent across rounds
in each competition, with 16 of 21 rounds hav-
ing more red than blue winners, and only four
rounds having more blue winners (sign test,
P0.012). The effect is the same across the
weight classes in each sport: 19 of 29 classes
had more red winners, with only six classes hav-
ing more blue winners (sign test, P0.015).
(For methods, see supplementary information.)
Given the undoubted role of other factors,
such as skill and strength, it is likely that the
red advantage will determine the outcome
only in relatively symmetric contests. That is,
wearing red presumably tips the balance
between losing and winning only when other
factors are fairly equal. We found that this is
indeed the case: only in contests between indi-
viduals of similar ability were there signifi-
cantly more red than blue winners (
2
6.07,
d.f.1, P0.014), with the red advantage
seeming to decline as asymmetries in compet-
itive ability increase (Fig. 1b). Hence, although
the effect is significant for the pooled data
shown in Fig. 1a, this is due principally to the
results for relatively symmetric contests.
These results indicate that artificial colours
may influence the outcome of physical con-
tests in humans. A preliminary analysis of the
results of the Euro 2004 international soccer
tournament, in which teams wore shirts of dif-
ferent colours in different matches, suggests
that wearing red may also bestow an advantage
in team sports and when opponents wear
colours other than blue. We compared the per-
formance of five teams that wore a predomi-
nantly red shirt against their performance
when wearing a different shirt colour (four
played their other matches in white, one in
blue). We found that all five had better results
when playing in red (paired t-test, t3.15,
d.f.4, P0.034), largely as a result of scoring
more goals (t2.98, d.f.4, P0.041)
(further details are available from the authors).
Hence, colour of sportswear may affect out-
comes in a wide variety of sporting contexts.
Colour is thought to influence human
mood, emotions and expressed aggression, and
is a recognized element of signalling in com-
petitive interactions in many non-human
species. But it has not hitherto been suspected
to be a factor in human contests. Given the
ubiquity of aggressive competition throughout
human societies and history, our results sug-
gest that the evolutionary psychology of colour
is likely to be a fertile field for further investiga-
tion. The implications for regulations govern-
ing sporting attire may also be important.
Russell A. Hill, Robert A. Barton
Evolutionary Anthropology Research Group,
University of Durham, Durham DH1 3HN, UK
e-mail: r.a.hill@durham.ac.uk
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(1990).
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(2005).
4. Pryke, S. R., Andersson, S., Lawes, M. J. & Piper, S. E.
Behav. Ecol. 13, 622–631 (2002).
5. Andersson, S., Pryke, S. R., Ornborg, J., Lawes, M. J. &
Andersson, M. Am. Nat. 160, 683–691 (2002).
6. Cuthill, I. C. et al. Proc. R. Soc. Lond. B 264, 1093–1099
(1997).
7. Drummond, P. D. & Quah, S. H. Psychophysiology 38,
190–196 (2001).
8. Darwin, C. The Expression of the Emotions in Man and
Animals (Murray, London, 1872).
9. Drummond, P. D. Pers. Indiv. Diff. 23, 575–582 (1997).
10. Ryan, M. J. in Behavioural Ecology (eds Krebs, J. R. &
Davies, N. B.) 179–202 (Blackwell Science, Oxford, 1997).
doi: 10.1038/435293a
Supplementary information accompanies this
communication on Nature’s website.
Competing financial interests: declared none.
BRIEF COMMUNICATIONS
Figure 1 | Influence of colour of sporting attire on the outcome of competitive sports. a,Proportion of
contests in Olympic combat sports won by competitors wearing red (right bars) or blue (left bars)
outfits for all sports combined and for the individual sports of boxing (Box), tae kwon do (TKD),
Greco-Roman wrestling (G–R W) and freestyle wrestling (Free W).
b, Proportion of contests won by
competitors wearing red or blue given different degrees of relative ability (asymmetry) in the two
competitors in each bout. No significant differences exist between the number of red and blue wins
for contests with small (
2
2.21, d.f.1, P0.14), medium (
2
0.47, d.f.1, P0.50) or large
asymmetries (
2
0.21, d.f.1, P0.64) in competitive ability. Black lines at 0.5 indicate the expected
proportion of wins by red or blue under the null hypothesis that colour has no effect on contest
outcomes. For details of data collection and analyses, see supplementary information.
Degree of asymmetry
Small Medium Large
0.40
0.50
0.60
0.45
0.50
0.55
0.30
0.70
ba
Proportion of contests won
0.40
0.60
NoneAll Box TKD G–R W Free W
19.5 brief comms MH 13/5/05 9:53 AM Page 293
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