Design
The study was in 2 stages: first, we employed an independent
2-group comparison, comparing the clinical and the
nonclinical groups’ performance on the probabilistic reasoning
task; then we conducted a randomized experiment,
with only the clinical participants, who were
randomized either to the reasoning training intervention
or to an attention control activity, to compare changes
in reasoning, belief flexibility, and delusions before and
after intervention. All participants (clinical and nonclinical)
first completed assessments of intellectual functioning,
anxiety, depression, and data gathering. The clinical
participants also completed assessments of belief flexibility,
detailed assessments of the main delusion, and general
psychopathology. The clinical participants were then
randomized to receive a 45-minute reasoning intervention
or to an attention control condition consisting of
a neuropsychological assessment of comparable duration.
The same experimenter (K.R.) administered both
the training and the control conditions. After the administration
of the experimental training or the control activity,
the data gathering, belief flexibility, and delusion
assessments were repeated.