Orientation discrimination in WS 2

Orientation discrimination in WS 9

second experiment then further examines one aspect of mental imagery that could also
contribute to performance on Block Design tasks, namely the ability to transform a
mental representation.

Experiment 1

Method

Participants

Twenty-two individuals with WS and 22 typically developing children
participated in this experiment. This study took place approximately 8 months after
the previous study in which 21 of the WS group in this study had taken part (Farran et
al., 2001). The TD group were a different group of children, but recruited from the
same school as that used in the Farran et al. (2001) study. The two groups were
matched individually by performance on the RCPM (Raven, 1993), a measure of fluid
intelligence. This task is a non-verbal perceptual task in which participants are shown
a pattern or sequence in which a piece is missing. They are asked to choose which of
six choice pieces is the missing piece. Some of the distracter choices included are
reflections, orientations, and enlargements of the target, which raises the possibility of
matching away any differences in performance. However, as these distracter choices
occur infrequently, group differences in performance on experimental tasks should
not be masked by this matching procedure. Participant details are shown in Table 1.

Six members of the WS group had received a “fluorescence in situ
hybridisation” (FISH) test. This is a diagnostic test which checks for a deletion of the
elastin gene on the long arm of chromosome 7 which occurs in approximately 95% of
individuals with WS (Lenhoff, Wang, Greenberg, & Bellugi, 1997). All 6 cases
received positive FISH results, thus confirming a deletion of the elastin gene. None of
the WS participants had received negative FISH results. The remaining sixteen WS

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