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Proc. R. Soc. B
doi:10.1098/rspb.2009.2123
Published online
The quick and the dead: when reaction
beats intention
Andrew E. Welchman1,*, James Stanley2, Malte R. Schomers3,
R. Chris Miall1 and Heinrich H. Biulthoff4,5
1School of Psychology, University of Birmingham, Birmingham B15 2TT, UK
2School of Medicine, University of Otago, Dunedin, New Zealand
3Pembroke College, University of Cambridge, Cambridge CB2 1QA, UK
4Max Planck Institute for Biological Cybernetics, Tubingen, Germany
5Department of Brain and Cognitive Engineering, Korea University, Korea
Everyday behaviour involves a trade-off between planned actions and reaction to environmental events.
Evidence from neurophysiology, neurology and functional brain imaging suggests different neural bases
for the control of different movement types. Here we develop a behavioural paradigm to test movement
dynamics for intentional versus reaction movements and provide evidence for a ‘reactive advantage’ in
movement execution, whereby the same action is executed faster in reaction to an opponent. We
placed pairs of participants in competition with each other to make a series of button presses. Within-
subject analysis of movement times revealed a 10 per cent benefit for reactive actions. This was
maintained when opponents performed dissimilar actions, and when participants competed against a
computer, suggesting that the effect is not related to facilitation produced by action observation.
Rather, faster ballistic movements may be a general property of reactive motor control, potentially
providing a useful means of promoting survival.
Keywords: movement control; action observation; interpersonal competition
1. INTRODUCTION
The mythology of the American West is shaped by liquor
and Hollywood (Brown 1995). Inspired at least by the
latter, the Nobel laureate Niels Bohr considered why,
during a gunfight, the man who drew first was the one
to get shot. He suggested that the intentional act of draw-
ing and shooting is slower to execute than the reactive
action in response (Cline 1987), an idea grounded in
the everyday trade-off between stimulus-driven behaviour
and intentional, planned actions.
This distinction between different classes of action is
not merely semantic: evidence for differential neural
bases for intentional, as opposed to reactive, movements
is provided by neurophysiology (Kurata & Tanji 1985;
Romo & Schultz 1987; Mushiake et al. 1991; Maimon &
Assad 2006), neurology (Laplane et al. 1977; Halsband
et al. 1993; Cunnington et al. 1995; Sumner et al.
2007) and functional brain imaging (Deiber et al. 1999;
Jenkins et al. 2000; Cunnington et al. 2002). Further,
behavioural evidence points to a distinction between
different types of movement (Waszak et al. 2005), and
switching between these two modes of operation can
result in a cost (Obhi & Haggard 2004). However, here
we test whether there are benefits associated with reactive
movements, consistent with Bohr’s intuition and
the gunslingers legend.
To effect ‘laboratory gunfights’, we devised a relatively
simple task of button pressing that required a stereotyped,
* Author for correspondence ([email protected]).
Electronic supplementary material is available at http://dx.doi.org/10.
1098/rspb.2009.2123 or via http://rspb.royalsocietypublishing.org.
Received 20 November 2009
Accepted 14 january 2010 1
multi-segment movement. In particular, naive participants
made a speeded sequence of three button presses that
required a lateral movement of their hands (figure 1a).
The movement direction and sequence of button presses
was the same on every trial. Having become familiar with
this task, participants were paired with an opponent and
placed in competition (figure 1b). Opponents faced
each other with their own set of buttons before them and
held down the central button (button 1, ‘the home key’)
to start a trial. They were instructed that by executing
the movement and returning to their home key before
their opponent, they would score points from their
adversary.
To distinguish ‘initiated’ from ‘reactive’ movements,
we had to ensure that trials had no overt ‘go’ signal; other-
wise, all subsequent movements could putatively be
‘reactive’. Therefore, participants were forced to wait a
variable, non-signalled delay before initiating the move-
ment. If participants released the home key too early, a
tone sounded and the trial was aborted. The covert and
random nature of the start delay, and competition
between opponents, meant that each individual produced
some trials on which they initiated the movement
sequence (‘initiated’ movements) and other trials on
which they reacted to their opponent (‘reactive’
movements). Data analysis considered within-subject
differences in movement execution times. That is, we
compared the response of each individual under initiative
and reactive movement conditions, rather than consider-
ing the relative performance of different participants
and/or the outcome of interpersonal competitions. We
report results from three experiments. The first estab-
lishes the effect; the second tests whether faster
This journal is q 2010 The Royal Society