Orientation discrimination in WS 2

Orientation discrimination in WS 13

The two control groups in question had the same levels of nonverbal ability as
measured by the RCPM. The mean RCPM score for the control group who completed
the Squares construction task was 18.14 (S.D. =5.20), whilst the mean RCPM score
for the control group who were given the Squares discrimination task was 18.18
(S.D.=4.89). This was confirmed statistically though independent t-tests which
showed no significant difference between the scores of the two control groups
(t(41)=.025, p=.98).

One participant with WS had taken part in the Squares discrimination task, but
not the Squares construction task, hence they were excluded from this analysis. This
left data from each of 21 individuals with WS on the two tasks. Descriptive statistics
revealed similar levels of performance across the tasks in WS; Squares construction
task: mean = -1.09, S.D.= 1.46; Squares discrimination task: mean= -0.79, S.D.=
1.19. These z-scores for WS performance on the two tasks were compared using a
paired comparison t-test. This showed that the relative level of impairment of the WS
group on the two tasks did not differ significantly; t(20)=0.84, p=.41.

Discussion

The data from the Squares discrimination task indicate that, in terms of the
number of correct responses, individuals with WS were poorer than the TD controls,
but showed the same pattern of performance, i.e., poorer performance on the oblique
than the nonoblique trials. However, the RT analysis showed a variation between the
groups. Both groups took significantly longer to respond in the oblique trials than the
nonoblique trials, with a larger effect of obliqueness in the control group than in the
WS group.

In both these data and those of Farran et al. (2001) there was an interaction
between group and obliqueness in reaction times, but not in correct responses. We

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