The randomization schedule was generated using
www.randomisation.com and kept independently of
the experimenter. The experimenter was only informed
of the randomization allocation once the participant
had provided informed consent and an appointment
had been arranged for the testing.
Measures
Prerandomization. Wechsler Abbreviated Scale of Intelligence
General intellectual ability was assessed using
the 2-subtest version of the Wechsler Abbreviated Scale
of Intelligence (WASI) (vocabulary and matrix reasoning).
38 The 2-subtest version of the WASI takes approximately
15 minutes to administer and provides an
estimation of full-scale IQ.
Positive and Negative Symptom Scale. The Positive and
Negative Symptom Scale is a 30-item semistructured interview
designed to assess positive, negative, and general
psychopathology associated with schizophrenia.39
Respondents are asked to report the occurrence of symptoms
over the last 7 days. These are then rated according
to severity on a 7-point scale (1–7, ‘‘absent–extreme’’).
Higher scores indicate a greater presence of symptoms.
The positive and negative subscales are each calculated
by summing 7 items, while the general subscale is calculated
on the basis of 16 items.
Depression Anxiety Stress Scale. The Depression Anxiety
Stress Scale is a 42-item instrument with 3 subscales
measuring current symptoms of depression, anxiety, and
stress.40 Each of the subscales consists of 14 items with
a 0–3 scale (0 = did not apply to me at all, 3 = applied
to me very much). Higher scores indicate higher levels
of emotional distress.
Pre- and Postintervention Tests and Measures (Clinical
Group Only). Probabilistic Reasoning Task The probabilistic
reasoning task (also known as the ‘‘Beads
Task’’) is a standard task used to assess data gathering.16
Two computerized versions of the task were used. In version
1 (the 60:40 task), one jar had 60 red beads and
40 blue beads and the other jar had 40 red beads and
60 blue beads. In version 2 (the 85:15 task), one jar
had 85 red beads and 15 blue beads and the other jar
had 15 red beads and 85 blue beads. In both versions
of the task, participants were shown pictures of the 2
jars and told that one of the jars would be selected at random
by the computer and that beads would be drawn
from the selected jar. After each bead was drawn, participants
were asked if they would like to see more beads (ie,
if they would like more information) or if they could say,
with certainty, from which of the jars the beads were being
drawn. Once a bead had been drawn, it remained at
the bottom of the screen thereby providing a memory aid.
The key variable was the number of beads requested by
the participant before making a decision. JTC was classified
as requesting 2 or fewer beads. Both versions of the
task (60:40 and 85:15) were administered before and after
completion of the training or control tasks, but the color
of the beads used in each version were changed from pre
to post administration.