No abstract

the lack of age effects on the CET may be explained by the task dependence on "crystallised intelligence", which is less affected by healthy adult ageing than "fluid intelligence".

SUMMARY A simple technique is described for assessing the sensitivity of the human visual system to gratings at-threshold contrast. The technique has advantages for clinical use in that it is (1) inexpensive, (2) quick to administer, (3) portable, and (4) relatively free from bias. Forty-two diabetic patients and 84 normal controls have been tested. Fifteen diabetic patients (6/20 with retinopathy and 9/22 without) had test scores more than two standard deviations below the norm for age-matched controls.The threshold contrast at which a pattern of stripes is just visible is a measure of visual function that has recently received great attention. It differs from conventional acuity in several respects'-3 and can pick up deficits not detected by more conventional measures in lens4-5 and retinal6-"' pathology, glaucoma, 1-'5 retrobulbar neuritis,""' and other disorders.3 [19][20][21] The contrast threshold is best measured by electronically varying the contrast Halliday26 devised a printed contrast sensitivity test with four-alternative forced choice format, in which subjects were required to report the orientation of the stripes.Correspondcncc to Dr A J Wilkins.

A non-verbal problem solving task, viz. a simplified version of Shallice's London Towers Test, was given to 131 normal subjects to obtain normative data relating to age, education and sex. The test was built up in its easiest possible feature in order to be administrable also to demented patients, therefore possibly becoming part of the neuropsychological diagnostic procedures of the demential syndromes. Although this version of the test proved to be very easy and therefore likely to yield a statistically treatable wide distribution of scores in demented patients, the age-related decline of performance in normals was apparent. Education and sex showed no significant influence on the test-performance. With correction of the raw scores for age and with knowledge of the distribution of scores in the normal population, this test is now ready to assess the normality of the scores of a new subject according to his age, giving information on this otherwise still uncovered sector of cognitive abilities.