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significantly greater in the hypnotized condition (see Table 1). This
supports the conclusion that the process of sustained attention control
is diminished in the hypnosis condition.
Similarly, color-naming reaction times are significantly greater in the
hypnotized condition than in the nonhypnotized condition, replicating
the findings of Sheehan et al
.
(1988). This finding should now be
considered an empirically well-founded result, even though it is in
the opposite direction to that predicted by the widely held view that
hypnosis requires strongly engaged and highly efficient frontal net-
works of attention control.
The color-naming reaction-time score has been criticized as an
unambiguous indicator of the process of suppressing attention (Dixon
,
Brunet, & Laurence, 1990). The color-naming reaction-time score may
also reflect general changes in reaction time, as well as specific changes
in suppressing attention processes. In the present study, word-naming
reaction times also increased significantly in hypnosis. Future research
will need to include more conventional color- and word-congruent
Stroop stimuli in order to resolve this issue. However, total error rates
(incorrect responses) were also utilized in the present study to provide
a convergent check on the interpretation of hypnosis effects on color-
naming as effects on the operation of suppressing attention processes.
Because an error will occur by giving the word when the color is
required or by giving the color when the word is required, each error
results from a failure to suppress a competing response. Thus, total
error rates represent an alternative measure to color-naming reaction
times to index the operation of suppressing attention processes.
Total error rates did, in fact, show a significant increase during
hypnosis. However, unlike color-naming reaction times and time-outs
(but like experiential set ratings), there was also a significant effect for
susceptibility and a significant interaction effect between susceptibility
and hypnotic instruction. Total error rates were significantly higher in
the hypnotized condition for high but not for low hypnotically suscep-
tible groups.
The efficiency of suppressing attention is not significantly dimin-
ished in the hypnotic context for low susceptibles. It is only for high
susceptibles that efficiency in suppressing attention declines signifi-
cantly during hypnosis. This objective decline in cognitive task per-
formance is paralleled by a change in the subjective quality of
awareness, in line with Tellegen’s (1981) description of the experiential
set. Though using different methodologies and much smaller samples
increased response conflict errors in hypnosis have also been reported
by Kaiser, Barker, Haenschel, Baldeweg, and Gruzelier (1997) and
Nordby, Hugdhal, Jasiukaitis, and Spiegel (1999).
The ‘‘relaxation’’ and ‘‘effortful concentration’’ instructional condi-
tions sought to address the effects of relaxation. The use of preparatory
AN EMPIRICAL TEST OF DISSOCIATED CONTROL
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