Políticas en Formación Inicial del Profesorado: Educación Primaria y Secundaria.

Measurement of visual perceptual functions is complex. However, neuropsychological tests involving visual function are among the strongest correlates with practical driving test criteria. There are many aspects of visual perception which may be affected by neuropsychological impairment, and a range of psychological tests are available which assist in discriminating deficit in visual perceptual functions (Lezak, 1 995). These tests

are separate from standard tests of visual acuity, some of which are inherent in licensing procedures and medical examinations for driving fitness. With the use of psychological tests, measurement of visual perception typically overlaps with tests of orientation and attention, as well as those involving higher level executive functions. Thus , only by using different modalities, conditions, or combinations of functions, is an understanding of the nature of impairment gained (Banich et al., 1 990; Lezak,

1 995 ) .

Poor performance o n visual perceptual tasks i s found i n a number of clinical groups, as these abilities are affected by a wide range of impairments (Walsh, 1 994). However, it has been suggested that since visuospatial and visuomotor functions are typically disrupted as a result of right hemisphere damage (Lezak, 1 995), this may explain the lower success rate of left hemiplegic subjects in driver assessment (van Zomeren et al., 1 987). Visual perceptual tasks are considered relevant to driving, and deficits in this area are among the more significant predictors of poor performance on practical driving measures for neuropsychologically-impaired drivers ( Priddy et al. , 1 990; Quigley & DeLisa, 1 983; Sivak et a! , 1 98 1 ; van Wolffelaar et al., 1 987). Yisuospatial and visuomotor functions, in particular, have been highly correlated with outcome on several driving tests. Importantly, research has also shown that improvement in visual perceptual skills through training is related to increased driving performance over a standardised driving course (Sivak et al., 1 984 ).

Visuospatial a b i l ities. One-, two- or three-dimensional tracking tasks are commonly used to measure visuospatia1 abilities of neuropsychologically-impaired drivers. These range from pen and paper maze tests (with an orientation component) to more face valid, in-car tests of lateral position control. The latter have obviously been developed specifically for driver assessment, but are poorly standardised compared to more traditional tests of visual perception. Computerised tracking tasks have also gained popularity as prerequisite measures in the assessment of neuropsychologically­ impaired drivers, and have been significantly correlated with measures of practical driving ability (Gianutsos, 1 99 1 , 1 994; Jones et al., 1 983). Some evidence is available for criterion-related validity of the various forms of tracking measures. Lateral position control ( measured as constant speed tracking in highway traffic), is significantly correlated with other tests containing visuospatial and visuomotor components, including the Benton Visual Retention Test-Revised (BVRT-R), Trailmaking A, and the

COGNITIVE MEASURES

Minnesota Rate of Manipulation Test (van Zomeren et al., 1 988). Compared with other neuropsychological tests containing visuospatial and visuomotor components, in-car lateral position control tasks are more often correlated with other practical driving measures (van Wolffelaar et al., 1 988; van Zomeren et al., 1 988).

Visuospatial abilities are also commonly measured through speeded tests which involve connection between items and symbols, such as Trailmaking A and B . In relation to actual driving cri teria, results of these tests are mixed. For example, the Tactual Performance Test together with Trailmaking A and B , significantly differentiated successful and unsuccessful candidates on a practical driving evaluation (Brooke et al., 1 992) . In the same study, however, other dri ving criteria, based an examiner's j u dgement of whether drivers were safe or not safe, did not correlate with the neuropsychological test scores. Galski et al. ( 1 993) found that time to complete Trailmaking A was highly significant in predicting outcome on practical driving criteria. In another study, Rothke, ( 1 989) found that the Trailmaking A and B test did not correlate with outcome on a practical driving examination. Further, van Zomeren et al. ( 1 988), found that although the Trailmaking A and B test did not differentiate success or failure on the Test for Advanced Drivers, there was a highly significant relationship between in-car lateral position control and both of these measures.

Visual recognition. Assessment of visual perception also includes tests of visual recognition. In this category, tests such as Judgement of Line Orientation have correlated significantly with driving status (Priddy et al., 1 990). S imilarly, Galski et al . ( 1 993 ) reported that number of errors on the Visual Form Recognition Test was a highly significant predictor of outcome on a practical driving assessment. Van Wolffelaar et al . ( 1 987) found that Judgement of Line Orientation and the Benton Visual Retention Test (BVRT-R) were the only significant clinical variables relating to performance on the standardised 'Test for Advanced Drivers'.

Complicated recognition tasks may also include elements of visual interference, as measured by figure ground tests (Lezak, 1 995). Results for the commonly u sed Embedded Figures test are usually significantly lower for neuropsychologically­ impaired groups compared with controls, but do not reach a level of significance in relation to any practical driving measures (Sivak et al., 1 98 1 ; van Wolffelaar et al., 1 987). Interesting results come from an early study of normal drivers, where the

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Embedded Figures test was significantly related to perceptual style (Mihal & B arrett, 1 976). Unfortunately, this finding has not been investigated further, nor in relation to drivers who are neuropsychologically impaired.

Other tests of visual interference cited in the neuropsychologically-impaired driver literature include Overlapping Lines and the Southern California Figure Ground test (Hartje et al ., 1 992; Sivak et al., 1 98 1 ). In these studies, both tests significantly differentiated experimental groups from controls and were close to significant in determining driving assessment outcome.

Visual neglect and scanning. Additional visual perceptual abilities considered to be important to behaviour in traffic include visual neglect or i nattention, and visual scanning (Hartje et al., 1 992; Quigley & DeLisa, 1 983). Fewer formal measures are available to assess these functions, although they may be inherent in tests of attention span and information processing speed (Hartje et al., 1 992; van Zomeren et al., 1 988). I nformal measures, such as hazard identification from slide or videotape presentations of traffic situations, and other forms of driving simulation may also provide useful information (Hopewell & Price, 1 985; Gouvier et al., 1 989). Unfortunately, research in this area has not really progressed from the early stages of developing standardised measurement techniques, and results are unclear in relation to practical driving criteria.

Visuomotor a b i l i ties. The measurement of visual perceptual abilities for neuropsychologically-impaired drivers also enters the domain of motor functions . Tasks with a visuomotor component typically involve measurement of mental speed and coordi nation, in tests such as Trailmaking A and B , the Minnessota Rate of Manipulation Test, and various reaction time measures. These tests have all been correlated with real driving criteria (van Wolffelaar et al., 1 987). However, many of these tests measure other aspects of visual ability and may also be used to assess executive functioning. Therefore problems exist with separating out possible confounding effects of the different functions. Similarly, where motor functions are being assessed, there is the need to ensure that these are not confounded with more general motor disturbances (Lezak, 1 995). In driving assessment, the latter tend to be the realm of the occupational therapist, and are sometimes responsive to the use of adaptive driving aids.

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