The four subtests that make up Bannatyne's Spatial Ability category (three of which compose the Perceptual Organization index) are also measures of simultaneous processing, the kind of gestalt-holistic problem-solving approach that cerebral specialization researchers associate with the right hemisphere and Luria adherents attribute to the occipital-parietal regions of the brain. Of the remaining Performance subtests, analytic, linear, left-brain processing is best measured by Digit Symbol-Coding. Other measures of sequential processing are found on the Verbal scale: Digit Span, Letter-Number Sequencing, and Arithmetic. Consequently, a possible configuration of the Performance scale is for the four simultaneous processing subtests to split off as a cluster, with the individual performing about equally well on Digit Symbol, Symbol Search, and Picture Arrangement (either substantially higher or lower than on Picture Completion-Block DesignMatrix Reasoning-Object Assembly).
The occurrence of this sequential-simultaneous dichotomy may be checked by investigating the individual's level of performance on the Verbal tasks that measure sequential processing (Digit Span, Letter-Number Sequencing, and Arithmetic). Do not accept a processing explanation as viable for an apparent visual-spatial (simultaneous) versus visual-sequential dichotomy of the Performance scale unless the person evidenced a similar level of functioning (either high or low) on the verbal-sequential dyad. Further, examiners should not conclude that the individual has a simultaneous strength or weakness unless there is behavioral support for that contention. For example, did the person use a trial-and-error, sequential method of constructing puzzles and designs and placing pictures, or was an insightful, reflective, holistic problem-solving approach evident?
If verification of a processing interpretation of the Performance scale is lacking (from Verbal Scale scores or from clinical observations), one should explore other options. Even if Digit Symbol-Coding and Picture Arrangement pair up, this occurrence may be coincidental. Remember that each of these subtests has much subtest specificity (as does Matrix Reasoning). Hence, assigning unique or chance interpretations to fluctuations on Digit Symbol or Picture Arrangement may be defensible (an exception to our bias against subtest-specific inferences).
Relatively high scores on visual-spatial-simultaneous compared to visual-sequential tasks characterize autistic individuals. Lincoln et al.'s (1988) 33 nonretarded autistic children, adolescents, and adults (age range 8^2 to 29, mean age = 1712 years), tested on the WISC-R or WAIS-R, had a mean scaled score of close to 9 on the spatial triad versus a mean of about 6 on Picture Arrangement and Digit Symbol-Coding. The differential was similar in Rutter's (1978) autistic sample (means of about 653 and 3 ^3, respectively). In Rutter's sample, the deficiency on visual-sequential tasks was comparable to the group's deficit in verbal expression, although the nonre-tarded autistic group studied by Lincoln et al. showed its most striking weakness in expressive skills.
A group of 21 manic-depressives on lithium therapy performed poorly on WAIS visual-sequential tasks, especially Digit Symbol; the lowest scores on Picture Arrangement and Digit Symbol were obtained by patients who had been on lithium the longest (Nair et al., 1979). In addition, high simultaneous-low sequential Performance profiles have been found fairly consistently for patients with Huntington's disease. Consistencies among several samples of patients with this genetic disease imply that they truly have a strength in simultaneous processing coupled with a weakness in sequential processing. Huntington's patients typically earn their highest performance scaled score on Picture Completion, while evidencing depressions in Digit Symbol, Picture Arrangement, Arithmetic, and Digit Span (Brandt et al., 1984; Butters et al., 1978; Josiassen et al., 1982; Randolph et al., 1993).
The spatial-simultaneous grouping of subtests (excluding Matrix Reasoning, because none of the studies were based on the WAIS-III) has also been found to be of clinical significance for a different sample with motor coordination problems: patients with multiple sclerosis (Heaton et al., 1985; Maurelli et al., 1992). All five WAIS-R Performance subtests (versus only two of six Verbal tasks) discriminated significantly between normal adults and patients having multiple sclerosis. But only Block Design, Object Assembly, and Picture Completion significantly discriminated between two samples of multiple sclerosis patients, one with relapsing-remitting symptoms, the other having chronic-progressive multiple sclerosis. Interpretation of the simultaneous subtests requires some caution. Although performance on the tasks has been positively associated with a field-independent cognitive style (Good-enough & Karp, 1961), there is some evidence, based partly on WAIS Block Design data, that the two constructs (spatial ability, field-independent cognitive style) are indistinguishable from one another (MacLeod, Jackson, & Palmer, 1986). Further, as discussed in Chapter 4 on individual differences, there is a significant gender difference, favoring males, in visualization.
Sometimes Block Design is a maverick subtest regarding its processing demands. Matrix Reasoning, Picture Completion, and Object Assembly stress the synthetic, visual closure skills that are so closely associated with a simultaneous processing approach to problem solving. Block Design demands this synthetic ability, but it also makes heavy demands on analytic ability, espe cially when constructing the designs from the two-dimensional cards with the guidelines removed. On these items, individuals must first effectively analyze the design into its component parts before they can synthesize a solution. The relevance of both processing styles has been demonstrated both in neuropsychological research and practice (Lezak, 1995). Matarazzo (1972) noted: "Oddly enough, individuals who do best on the test are not necessarily those who see, or at least follow, the pattern as a whole, but more often those who are able to break it up into small portions" (p. 212).
Support for Block Design's analytic component comes from experimental psychology research conducted by Schorr, Bower, and Kiernan (1982) with 10 undergraduate students from Stanford included in each of three studies. These authors distinguished between two types of strategies, one more simultaneous (synthetic), the other more sequential (analytic). The synthetic style involves holistic pattern matching; the analytic style demands mentally segmenting each block in the design. Results of each study indicated the predominant application of analytic problem-solving strategies. Although Royer (1984) challenged the use of the analytic-synthetic typology by Schorr et al., these investigators responded cogently to Royer's criticisms (Kiernan, Bower, & Schorr, 1984). Although one cannot generalize much from data obtained on a group of undergraduate students at a highly rated university, it is clear that Block Design items can be solved efficiently by sequential approaches, simultaneous approaches, or a combination of the two.
Sometimes, therefore, Block Design must be deleted when conducting a processing analysis of the Performance scale. Like Picture Arrangement and Digit Symbol-Coding, Block Design may be solved sequentially or by an integration of processes; and, like the two visual-sequential subtests, Block Design demands good verbal comprehension of lengthy verbal directions read by the examiner. Matrix Reasoning also has an analytic component that comes into play when dealing with each stimulus separately, and verbal mediation is a common strategy for solving the abstract reasoning problems. Picture Completion and Object Assembly, by contrast, depend more heavily on the gestalt function with minimal emphasis on analysis or on the so-called left-brain function of interpreting lengthy verbalizations or verbal mediation. Examiners should be alert for the emergence of the Picture Completion-Object Assembly dyad in Performance profiles. Should the appropriate configuration be detected, this visual closure dyad should be contrasted to the visual-sequencing subtests (Picture Arrangement, Digit Symbol-Coding) and, perhaps, to the pair of tasks that emphasize an integration of sequential and simultaneous processing (Block Design, Matrix Reasoning).
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Whenever a doctor informs the parents that their child is suffering with Autism, the first & foremost question that is thrown over him is - How did it happen? How did my child get this disease? Well, there is no definite answer to what are the exact causes of Autism.