A failure of conflict to modulate dual-stream processing may underlie the formation and maintenance of delusions.
BACKGROUND
Dual-stream information processing proposes that reasoning is composed of two interacting processes: a fast, intuitive system (Stream 1) and a slower, more logical process (Stream 2). In non-patient controls, divergence of these streams may result in the experience of conflict, modulating decision-making towards Stream 2, and initiating a more thorough examination of the available evidence. In delusional schizophrenia patients, a failure of conflict to modulate decision-making towards Stream 2 may reduce the influence of contradictory evidence, resulting in a failure to correct erroneous beliefs.


METHODS
Delusional schizophrenia patients and non-patient controls completed a deductive reasoning task requiring logical validity judgments of two-part conditional statements. Half of the statements were characterized by a conflict between logical validity (Stream 2) and content believability (Stream 1).


RESULTS
Patients were significantly worse than controls in determining the logical validity of both conflict and non-conflict conditional statements. This between groups difference was significantly greater for the conflict condition.


CONCLUSIONS
The results are consistent with the hypothesis that delusional schizophrenia patients fail to use conflict to modulate towards Stream 2 when the two streams of reasoning arrive at incompatible judgments. This finding provides encouraging preliminary support for the Dual-Stream Modulation Failure model of delusion formation and maintenance.
Speechley
W J
WJ
Department of Psychiatry, The University of British Columbia, Vancouver B.C., Canada.
Murray
C B
CB
McKay
R M
RM
Munz
M T
MT
Ngan
E T C
ET
D000328:Adult; D016022:Case-Control Studies; D003071:Cognition; D003220:Conflict, Psychological; D003657:Decision Making; D003702:Delusions / Q000523:psychology*; D004644:Emotions; D005260:Female; D006801:Humans; D008128:Logic; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D011581:Psychological Tests; D012565:Schizophrenic Psychology; D013647:Task Performance and Analysis