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and Stroop-type tasks indicate that regions of both the anterior cingulate
cortex (ACC) and the left dorsolateral prefrontal cortex (lDLPFC) are
consistently activated in conditions requiring the resolution of conflict-
ing-response tendencies (Banich et al., 2000; Botvinick, Nystrom, Fissell,
Carter, & Cohen, 1999; MacDonald, Cohen, Stenger, & Carter, 2000;
Milham et al., 2001; Milham, Banich, Claus, & Cohen, 2003).
Woody and Bowers (1994) frame dissociated-control theory speci-
fically in terms of the SAS model of executive control and the disruption
of functional interactions between anterior and posterior cortical net-
works. In view of current models of Stroop-type tasks (e.g., see
MacLeod & MacDonald, 2000), Kirsch and Lynn (1998) proposed that
it was particularly appropriate to test dissociated-control theory utiliz-
ing the Stroop paradigm. They specifically predict that, on the bases of
dissociated-control theory, hypnotized persons should show impaired
performance on the Stroop color-naming task. Kirsch and Lynn point to
the existing work of Sheehan, Donovan, and MacLeod (1988) as a
possible test of this prediction.
Sheehan et al
.
(1988) administered the Stroop task to both high and
low susceptible participants during both no-hypnosis and hypnosis
conditions. In a later session, participants again performed the task
during hypnosis but after receiving strategy instructions aimed to
minimize Stroop interference. Thus, there were three experimental
conditions: no-hypnosis, hypnosis, and hypnosis plus strategy instruc-
tion. A significant effect was found for experimental condition, with the
hypnosis condition resulting in slower Stroop color-naming than the
no-hypnosis condition. A significant interaction was found between
experimental condition and susceptibility, with high susceptibles im-
proving (i.e., decreasing) reaction times in the hypnosis plus strategy
instruction condition relative to lower susceptibles. This finding sug-
gested to the authors that when instructed highs could more readily
focus their attention in hypnosis than could lows.
Sheehan et al. (1988) initially expected that hypnosis alone would
facilitate highly focused attending and expected a reduced Stroop effect
and thus a reduction in Stroop color-naming reaction times compared
to the no-hypnosis condition (at least for highs). The results obtained
were the direct opposite of this. They were however what Kirsch and
Lynn (1998) state should be predicted by dissociated-control theory.
The increase in the Stroop interference reaction times of high sus-
ceptibles during hypnosis was accompanied by a reduction in the
spontaneous use of strategies (which might have assisted participants)
and was reversed when highs were explicitly instructed to use a
specific strategy during hypnosis. The increase in Stroop interference
reaction times during hypnosis may have, in part, been due to the
decline in strategy-use, but it was not clear whether this was all or only
part of the story. The decline in strategy use may have caused the
234
GRAHAM A. JAMIESON
AND
PETER W. SHEEHAN
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