VALIDACIÓN MEDIANTE ESPECTRÓMETRO INDUSTRIAL

Goldstein and Scheerer (1941) thought that abstract and concrete thinking were

qualitatively different. There was no continuum of functioning. The brain damaged person was consigned to the lower level of concrete thinking. This view was challenged by Reitan (1958b, 1959b), who reported findings on the Category test of the Halstead-Reitan

Battery, which is described in detail in section 1.10. Patients could improve their performance on this test of abstraction after experience with the test stimuli. If they no longer had access to the higher planes of abstract thought, as Goldstein and Scheerer (1941) had claimed, such improvement would not have been possible. In the face of Reitan’s evidence, Goldstein suggested that some patients only differ quantitatively from normal functioning, wheras others are restricted to a qualitatively different level of conceptual thought (Goldstein, Neuringer and Olson, 1968).

Later work studying patients with acquired brain damage has continued to focus on the different sytems which might mediate the application of learned information and the solution of new problems. Shallice (1982) suggested that a supervisory attentional system was necessary for novel problem solving and that this system was disrupted by prefrontal lesions. Routine selection of stored information could be achieved without the integrity of the supervisory attentional system. Shallice’s model implies that conventional intelligence tests will fail to expose deficits in the supervisory system, if they largely measure

established cognitive routines and do not present novel problems for solution.

Aphasia and abstraction

There is some evidence that aphasie deficits are related to poor performance on tests of abstraction. For example, McFie and Piercy (1952) showed that patients with left hemisphere lesions did less well than right hemisphere cases on the Weigl sorting test (Weigl, 1927). However, within the left hemisphere group, aphasies were no worse than non-aphasic patients. Costa and Vaughan (1962) also found that aphasia reduced

performance on the Weigl, leading them to suggest that even such an apparently non­ verbal test o f conceptual thinking might be helped by internal verbalization.

The lack of difference in performance between aphasie and non-aphasic patients on abstract reasoning tests led to the suggestion that the dominance of the left hemisphere for intellectual tasks was independent of its dominance for language. Other workers

around this time reported ahasic patients performing significantly worse that non-aphasic patients on several tests thought to measure non-verbal reasoning. Colonna and Faglioni (1966) used Elithom's Maze Test (1955).

De Renzi et al (1966) found that not only did aphasie patients perform poorly on a transformed Weigl, with five criteria of classification, but their scores varied with the severity of their comprehension deficit. The discrepancy held true when the groups were equated with respect to their score on a general intelligence test. Raven’s Progressive Matrices (described in section 1.6C).

Russo and Vignolo (1967) used one of the earliest tests of spatial thought, the Gottschaldt test, which required subjects to identify an abstact shape fi'om within a complex geometric mask. Goldstein (1927) thought that this task related to more than just spatial competence, and tapped a more general capacity to isolate a coherent concept fi'om within any

distracting context.

In perhaps the most thorough investigation of this test with brain damaged people, Russo and Vignolo (1967) tested four groups of subjects: normal controls, non-aphasic patients with left hemisphere damage, aphasie patients with left hemisphere damage and patients with right hemisphere damage. Not only were the last two groups impaired compared to the first two, but the aphasie patients were significantly worse than the patients with right hemisphere damage. A similar finding was reported by Weinstein and Teuber (1957).

Benowitz et al (1990) used a standardized battery to assess the cognitive functions of 41 patients who had suffered unilateral right hemisphere damage. Impairments in abstracting information ftom narrative pasages were as prevalent and as severe in magnitude as constructional apraxia. The extent of linguistic and visual-spatial deficits was highly correlated.

Vîlkki (1988) investigated whether anterior brain lesions caused more severe deficits of problem solving than posterior lesions. 57 patients were studied, divided into four

groups according to the quadrant of their lesion. The test material was eight plastic tokens, combining the features of red or blue, big or small and round or square. The tasks were comprehension, naming, categorization, identifying a hidden token by asking

questions about its features and a sorting task.

As would be expected, the left anterior-lesioned group were slower on the routine verbal operations and the anterior groups were significantly worse on the question and category tasks. Surprisingly, the anterior groups were not significantly worse on the sorting task, after the language deficits were taken into account. A sorting task so like the Wisconsin Card Sorting Task (Milner, 1963) would be expected to be equally reliable at

discriminating fi’ontal dysfunction. The finding emphasises the difficulty of assessing reasoning skills in neurological patients, where other necessary cognitive skills have also been affected and how subtle the interaction is between language and fluid intelligence.

Another quick test of abstraction that is extensively used clinically is the explanation of proverbs (e.g. Benton 1968). For example, a patient with concrete thought processes might explain the proverb “too many cooks spoil the broth” in terms of there being too many people in the kitchen. Clearly this test is vulnerable to aphasie deficits.

1 7C LOCALISATION OF FLUID INTELLIGENCE FUNCTIONS

As would be expected fi’om the contradictory findings regarding the role of aphasia in apparently non-verbal tests of reasoning, the evidence does not always support the functional division between the right and left hemispheres in terms of verbal and non­ verbal skills for reasoning tasks. McFie and Piercy (1952b) found that impairments on the Weigl test were more frequently found in left hemisphere cases. The Wechsler Similarities

test was also thought to involve abstraction and McFie and Piercy’s left hemisphere cases were more impaired on Similarities. The authors went on to conclude that “the process of abstraction is in fact specifically impaired by dominant hemisphere lesions."

The ftontal lobes and reasoning

The observed diflSculties of patients who have suffered lesions to the frontal lobes are often explained in terms of failures of reasoning. The pattern of deficits likely to be observed in a patient with frontal lobe damage is much less predictable than the patterns observed in association with damage to other areas of the brain. Among the reported signs accompanying frontal lobe damage are distractability, lethargy, overactivity, disinhibition, concrete thinking, failure to generate alternatives, generally disorganized behaviour, perseveration and failure to plan.

Although there is a strong feeling among clinicians that the frontal lobes subserve

reasoning to a significant degree, the research data (especially replication data) have often been disappointing. A recent review by McCarthy and Warrington (1990a) includes a summary of localisation studies for problem-solving tasks. There is a suggestion that tasks requiring the subject to generate strategies or display efiBdent use of high level motor ftmctions might be more closely associated with left frontal lobe damage. Because the evidence is so equivocal, the role of the frontal lobes in reasoning is considered separately and not within the sections devoted to the individual cerebral hemispheres.

Perhaps because of the complexity of the processes, the cognitive neuropsychology of the frontal lobes is, as yet, only at a tentative stage. Luria thought that language mediated and controlled attention and planning, writing extensively about the internalization of speech. He noted that patients with frontal lobe lesions often demonstrated a dissociation of speech and action and thought that this might be the primary cognitive defidt underlying the disordered behaviour of patients with frontal lobe lesions. However, many aphasie

patients can solve abstract problems (e.g. Warrington, James and Maciejewski, 1986). In addition, the planning failures can be restricted to verbal problems (e.g. Costello and Warrington, 1989).