Voluntary task switching under load: Contribution of top-down and bottom-up factors in goal-directed behavior
JELLE DEMANET
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FREDERICK VERBRUGGEN
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BAPTIST LIEFOOGHE
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ANDR VANDIERENDONCK
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Ghent University
, Ghent,
Belgium
The present study investigated the relative contribution of bottom-up and top-down control to task selection in the voluntary task-switching (VTS) procedure. In order to manipulate the efficiency of top-down control, a concurrent working memory load was imposed during VTS. In three experiments, bottom-up factors, such as stimulus repetitions, repetition of irrelevant information, and stimulus-task associations, were introduced in order to investigate their influence on task selection. We observed that the tendency to repeat tasks was stronger under load, suggesting that top-down control counteracts the automatic tendency to repeat tasks. The results also indicated that task selection can be guided by several elements in the environment, but that only the influence of stimulus repetitions depends on the efficiency of top-down control. The theoretical implications of these findings are discussed within the interplay between top-down and bottom-up control that underlies the voluntary selection of tasks.
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Many researchers assume that goal-directed behavior
relies on the intentional and controlled activation of task
goals (Baddeley, 1992; Logan & Gordon, 2001; Miller
& Cohen, 2001). However, several studies have
demonstrated that task goals can also be activated automatically
by information in the environment (e.g., Mattler, 2003;
Mayr & Bryck, 2007; Verbruggen & Logan, 2009) or by
the retrieval of previously formed associations between a
stimulus and a particular goal (e.g., Verbruggen & Logan,
2008; Waszak, Hommel, & Allport, 2003). In the
present study, we examined the contribution of top-down
and bottom-up activation of task goals in voluntary task
switching (VTS).
In VTS, participants switch between cognitive tasks.
They are free to select the task to perform, as long as
each task is selected an approximately equal number of
times and participants do not follow a predictable
pattern of task selection (Arrington, 2008; Arrington &
Logan, 2004, 2005; Liefooghe, Demanet, &
Vandierendonck, 2009; Mayr & Bell, 2006). A general finding is
that participants repeat tasks more often than they switch
(Arrington & Logan, 2005). This task-repetition bias has
been linked to the efficiency of top-down control
processes involved in the voluntary selection of task goals.
For example, Mayr and Bell argued that participants tend
to repeat tasks because the task on the previous trial is
still the most active one when a new task is selected. In
order to overcome this bias, the activated task has to be
inhibited. Thus, selection of tasks would depend on
topdown control processes (see also Arrington & Logan,
2004, 2005). However, several studies have shown that
bottom-up processes also contribute to task selection in
VTS (e.g., Arrington, 2008), and Mayr and Bell observed
that the task-repetition bias was stronger when the
stimulus of the previous trial was repeated than when the
stimulus alternated. This stimulus-repetition effect suggests
that voluntary task selection is not completely immune to
bottom-up priming effects.
In the present study, we focused on the contribution
of top-down control and bottom-up priming in
voluntary task selection. Studies in several paradigms have
shown that bottom-up factors contribute more to
behavior in cognitively demanding situations (for a review,
see Lavie, 2005). A manipulation that is often used to
reduce the efficiency of top-down control is a
concurrent working memory (WM) load (e.g., Logan, 2007). To
test the relative contribution of bottom-up and top-down
processes in task selection, we manipulated WM load in
the VTS paradigm in three experiments. Each
experiment consisted of two conditions: a load condition and a
no-load condition (see Logan, 2007). In the load
condition, participants were shown six letters that they had
to remember (study phase), followed by 13 voluntary
switch trials (VTS phase), followed by a recall phase, in
which participants had to indicate which letters they had
been shown in the study phase. In the no-load condition,
the study phase was immediately followed by the recall
phase, which, in turn, was followed by the VTS phase, so
that there was no concurrent memory load during the test
phase. We predicted that bottom-up control would
contribute more to task selection in the load condition than
in the no-load condition. The results of Experiment 1
confirmed this prediction and showed that the
stimulusrepetition effects and the task-repetition bias were
stronger in the load condition than in the no-load condition.
In Experiments 2 and 3, we further tested how stimulus
repetitions affected task-selection processes. We propose
three accounts for the stimulus-repetition effect. First,
the effect could be caused by the repetition of visual
information on the screen, which could prime the decision
to repeat the task (see also Arrington & Logan, 200 (...truncated)