Basic HTML Version
increase in Stroop interference reaction time during hypnosis or both
may have been caused by more fundamental changes induced by the
hypnotic condition.
In proposing the use of the Stroop task to test Woody and Bowers’s
dissociated-control theory, Kirsch and Lynn (1998) noted the initial
findings of Sheehan et al
.
(1988) but suggested that the effects of relaxation
induced by the hypnotic induction were the likely explanation. This
element must be accounted for in any test of dissociated-control theory.
A condition that requires the task to be performed in a relaxed manner
should also lower arousal levels relative to a condition that directs
participants to employ effortful concentration to perform the task. If
relaxation does explain the previously observed effects of hypnosis on
Stroop-task performance, then similar effects should also be observed in
the comparison between relaxation and effortful concentration.
Sheehan et al
.
(1988) found that color-naming reaction times in-
creased significantly in hypnosis for high susceptibles. At the same
time, the frequency of reported positional or rehearsal strategy use
dropped significantly in the hypnotized condition for high, but not for
low, susceptibles. When later given positional strategy instructions
during hypnosis, highs showed greater improvement (decrease) in
color-naming reaction times than lows. This suggests that changes in
strategy use accompany hypnosis and that strategy manipulation
affected color-naming reaction times. Since changes in color-naming
reaction times also accompany hypnosis, it is an open question as to
whether the effects of hypnosis on Stroop performance are a result of
changes in fundamental suppressing attentional processes or simply
the effects of changes in the adoption of facilitating strategies.
The following experiment, then, will examine various aspects of the
Stroop responses of high and low susceptibles in both hypnotized and
nonhypnotized conditions across five independent instructional con-
ditions. These will include a rehearsal-instruction condition and a no-
strategy-instruction condition (i.e., use no strategy). Also included will
be an effortful-concentration-instruction condition and a relaxation
condition. Finally, in order to determine how each condition departs
from a neutral baseline, a no-instruction contrast group will be used for
comparison.
Participants’ self-reported use of rehearsal, experiential, and posi-
tional strategies will be examined, together with several aspects of
Stroop performance (color-naming reaction times, word-naming reac-
tion times, and time-outs). In addition, error responses will be analyzed
as an alternative measure of the efficiency of suppressing attention as
distinct from reaction times alone.
The Stroop paradigm adopted by Sheehan et al. (1988) is especially
difficult, containing only incongruent trials and frequent changes
between word-naming and color-naming instructions. This paradigm
AN EMPIRICAL TEST OF DISSOCIATED CONTROL
235
Downloaded by [ ] at 05:16 26 March 2012