[1] Automatic
and unconscious processes are traditionally regarded as inflexible (e.g.,
Shiffrin and Schneider, 1977, 1984), quite distinct in quality from the
flexible nature of “voluntary” processes. However, there is increasing evidence
that automatic and subliminal processes can in fact be modulated by “top-down”
processes of attention, intention (“task set” or current goals) and
expectation.
[2] DISSOCIATIONS IN
AUTOMATIC AND VOLUNTARY CONTROL
Recent
work from Boy et al. (2010b) suggests that the important distinction is not
between control that is automatic compared to control that is voluntary, but
rather between pre- and poststimulus
control
[3] PRE-STIMULUS VS.
POST-STIMULUS COGNITIVE CONTROL
Control
mechanisms that can override inappropriate response plans which have been
automatically evoked by the environment not only act to inhibit responses after they have
been evoked by the stimulus. Pre-stimulus control
mechanisms also seem to play a role. Thus, task set and previous experience can
modulate conflicting response tendencies in a preparatory manner.
[4] EVIDENCE FOR
AUTOMATIC ACTIVATION OF MOTOR RESPONSES
Perceptual processing of a visual stimulus can
result in motor responses even when the observer does not intend to act. One of
the most well-studied of these phenomena is the “visual grasp reflex”, where an
observer makes a fast, reflexive eye movement (saccade) toward a suddenly
appearing—and irrelevant—visual stimulus, despite their intention to look
elsewhere (e.g., Theeuwes et al., 1998; Irwin et al., 2000). ... But as
response latencies increase, saccades are more likely to curve away from a distractor (e.g.,
Walker et al., 2006), revealing an inhibitory mechanism acting to suppress
unwanted motor activity toward the irrelevant stimulus (e.g., Sheliga et al.,
1995).
[5] EVIDENCE FOR
AUTOMATIC MOTOR ACTIVATION FROM “PARTIAL” ERRORS
However, it is possible that small amounts of
force applied (erroneously) to a button might be insufficient to trigger a
measurable response and thereby escape detection. ... trials provides strong evidence that an
irrelevant stimulus—or part of a stimulus—can automatically activate responses
associated with it. These responses are not merely partially activated
somewhere in the brain; the response can be measured in the muscles or in small
hand movements with force transducers.
[6] INVISIBLE
INFLUENCES
In summary, shifts of attention and motor
responses can be automatically and unconsciously triggered by visual stimuli.
Effects of non-perceived stimuli such as these have provided key evidence that
visual stimuli can automatically prime the observer to act.
[7] INHIBITION OF
PRIMED ACTIONS
Thus, it is necessary to consider how brain
systems inhibit or override responses that have been triggered automatically by
the environment and are not relevant to our current goals....Processing by the
fast, direct
processing route is
automatic, and occurs irrespective of task instructions. For
example, the spatial location of a target stimulus in a Simon task would be
processed quickly and automatically via the direct processing route. At the
same time, processing of the task-relevant target attribute (e.g., target color
in a Simon task) proceeds via a slower indirect processing route. On
congruent trials, the same response is activated by both the direct and the
indirect processing routes, producing fast, correct responses. On incongruent
trials, however, the direct processing route and the indirect processing route
activate different responses which results in increased error rates, and slower
response times as the conflict between competing responses is resolved.
... Importantly, models of
information processing in conflict tasks often include an active inhibition
mechanism which acts to selectively suppress inappropriate response activation
resulting from the direct processing route...
In conflict tasks, accuracy for compatible
trials is near-perfect, while fast responses on incompatible trials are often
near (e.g., Wylie et al., 2009) or below (e.g., Stins et al., 2007) chance
level.
...that erroneous responses are
activated quickly via the direct processing route, before being selectively
suppressed by an inhibitory control mechanism.
[8] UNCONSCIOUS
CONTROL OVER UNWANTED RESPONSES
inhibition of primed responses only operates
when stimuli are presented above—and not below—the threshold required for
conscious awareness (e.g., Merikle et al., 1995 using the Stroop task). However, when the interval between prime and
mask was extended beyond around 100–150 ms, incompatible trials produced faster
responses than compatible trials. In other words, the usual priming effect had reversed. This negative compatibility effect (NCE) has now been widely
reported with button-press responses, foot responses, and eye movements
... Many
researchers have suggested that this reversed priming results from an
inhibitory mechanism in the motor system which acts to suppress sub-threshold
motor activation evoked by the prime
[9] AUTOMATIC
INHIBITION IN THE AFFORDANCE PARADIGM
visual
stimuli automatically evoke motor responses, Overall, these studies suggest
that actions which have been automatically primed by object affordances may
also be subject to automatic control.
[10]
AUTOMATIC TRIGGERING OF “ENDOGENOUS” CONTROL
However,
recent work suggests that endogenous suppression of pre-potent responses can
also be primed or evoked unconsciously and automatically (e.g., Verbruggen and
Logan, 2009a; van Gaal et al., 2008, 2009, 2010a,b).
[11]
AUTOMATIC PRE-STIMULUS CONTROL
Many
researchers have suggested that observers must consciously experience conflict
in order for the pre-stimulus control mechanisms to be deployed (e.g., Kunde,
2003; Mayr, 2004; Ansorge et al., 2011). However, recent evidence from van Gaal
et al. (2010a) suggests that some pre-stimulus control can be evoked
automatically, without conscious awareness. ...unconsciously presented stimuli
can automatically evoke these pre-stimulus conflict adaptation mechanisms, and
can modulate the effects of subsequent conflicting stimuli.
[1] Jennifer McBride1*, Frédéric Boy2, Masud Husain1 and
Petroc Sumner2 ‘Automatic motor activation in the
executive control of action’
1 Institute of Cognitive Neuroscience and Institute of
Neurology, University College London, London, UK
2 School of Psychology, Cardiff University, Cardiff, UK
