The genetic relationship between intelligence and components of cognition remains controversial. Conflicting results may be a function of the limited number of methods used in experimental evaluation. The current study is the first to use CANTAB (The Cambridge Neuropsychological Test Automated Battery). This is a battery of validated computerised cognitive tests, which allows assessment across a number of domains. A sample of 278 female-female Caucasian twin pairs from the UK (aged 18-76) performed such tests to establish the importance of genetic factors on four composite cognitive measures: general memory ability, inspection time (IT), working memory, and reaction time (RT). Estimates of heritability (additive genetic variance) were found to be 57% (95% CI 44, 68) for general memory, 38% (23, 51) for IT and 31% (16, 45) for working memory. The National Adult Reading Test (NART), a measure of IQ, had a heritability of 76%. RT was explained by common environmental influences and nonshared environmental influences. Moderate phenotypic correlations between general memory and NART (r = 0.32) and general memory and working memory (r = 0.42) were also reported. Both relationships could be explained by shared genetic determinants.