The name is absent

Conditioned Blocking: Schizophrenia

situation better than non-paranoids because they switch in an active controlled processing
strategy (Heim, 1989). This explanation could underlie our finding that PH patients showed
a CB impairment on the first trial, but thereafter used a normal CB strategy—through
switching in controlled processing. Indeed our finding that NP patients learned more about
the added stimulus could be viewed as the automatic response of a perceptual strategy. Our
discussion of the “stereotyped” response of PH patients to context and of NP patients to
task demands (above) also supports this distinction.

There have been numerous failures to find performance differences between paranoid
and non-paranoid patients (e.g. Hoff et al., 1992; Rund et al., 1993) and yet many others that
have reported “poorer” performance on psychological tests in non-paranoid vs paranoid
patients (e.g. Ditchfield & Hemsley, 1990; Neufeld & Williamson, 1994). There is no
necessary inconsistency here. If NP patients have fewer processing resources available and
are more likely to use automatic processing then there are many task forms that will show
an impairment. We should emphasize that in the CB task NP patients actually learned
more about the added stimulus than the other groups. It is this which was unusual.

The end result is that paranoid patients may not be so deviant in co-ordinating attention
(Scherer & Storms, 1981). The difference may lie in the means they use to achieve this end.
We would not take issue with Liddle’s (1987) view that patients with poverty symptoms
(cf. NP) are impaired in conceptual processing. In CB such an ability requires controlled
parallel processing that was not an attribute of our NP patients. However, it may well be,
as in other attentional tasks (Rappaport et al., 1972), that the PH patients were more able
to use a normal attentional strategy than NP patients as they were more responsive to
medication. We now consider this aspect in the last part of the discussion.

Monoamine Activity and Medication

Medication

Neuroleptic treatment is considered to be mildly beneficial on information processing and
attention span (Spohn & Strauss, 1989). Here we found no dose-performance relationship.
However, a clinical response to neuroleptics may have been important. HVA increases
implied that the PH patients were responding to medication more than the NP group and
we have noted that animals treated with neuroleptics show facilitated performance on
learned inattention tasks (see Introduction). The curious implication that anticholinergic
medication may be beneficial for CB in 14 patients is probably an artifact as most received
the same dose. Spohn & Strauss (1989) noted that anticholinergic medication impairs recall
rather than recognition processes. The latter rather than the former is important for
performance of the present task.

Monoamines

It is important to note that 25-30% of HVA measured peripherally may reflect central
DA metabolism with most of the remainder being derived from NA metabolism (for a
review see Amin et al., 1995). Thus, as HVA∕DA and HVA∕MHPG ratios increased with
CB in the control group, it is assumed that increases of DA over NA metabolism were
responsible for the positive HVA∕MHPG correlation. However the reverse is probably the

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