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integrating processes. That is, a successful hypnotic induction results in
a change in how behavior (and cognition) is controlled.
To explain this change, Woody and Bowers turn to the supervisory
attentional system (SAS) model of Norman and Shallice (1986). In this
model, there are two types of control processes governing the operation
of cognitive schemata. Contention scheduling is the automatic process
whereby schemata compete through lateral inhibition for the control of
behavior and cognition. It is a decentralized process governing routine
operations and does not require conscious control. The SAS, however,
controls the production of nonroutine responses when the task is novel,
when strongly activated schema must be inhibited, when the required
schema is too weakly activated, or when selection among schemata is
required. The SAS modulates the operation of schemata by a process of
top-down activation and inhibition. This process also requires the SAS
to monitor the activation of relevant schemata.
The experience of volition is closely tied to the operation of the SAS.
When an action is controlled by the SAS, it is perceived as voluntary.
When an action is controlled by contention scheduling alone without
monitoring or modulation by the SAS, it is experienced as automatic.
Woody and Bowers (1994) explain accompanying changes in the
experience of volition by proposing that hypnosis (in high susceptibles)
results in a weakening of the operation of the SAS. Consequently,
environmental cues and coactive schemata dominate the control of
hypnotic responses (including cognition) through the process of con-
tention scheduling. This leads to the responses being experienced as
automatic or nonvolitional. On this account then hypnosis results in a
diminished capacity to initiate and maintain deliberate attentional
strategies.
Kirsch and Lynn (1998) have suggested a method for testing Woody
and Bowers’s theory. They propose that performance on the Stroop
color-naming task (Stroop, 1935) should decline in hypnosis if the
theory of diminished frontal supervisory attentional control is correct.
In this task, participants are shown color names (e.g., ‘‘red’’ or ‘‘green’’)
presented in actual colors. Participants are slower at naming the actual
color when it is incongruent with the color word. The Stroop task has
been analyzed by Stuss, Shallice, Alexander, and Picton, (1995) as an
operational measure of suppressing attention, the attentional control of
response conflict. This is one of the core functions of the SAS in their
extension of the Norman and Shallice model. ‘‘Suppressing attention is
required when automatic processes select schemata that are inap-
propriate to task performance’’ (Stuss et al., 1995, p. 200). Stroop-type
tasks create response conflicts in which a prepotent response to a highly
salient attribute (such as word name) must be suppressed in order to
allow response to another instructed stimulus attribute (such as actual
color). Functional magnetic resonance imaging (fMRI) studies of Stroop
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