However the same study says that for 3- to 5-year-olds, watching TV may actually improve some cognitive abilities.This is the result of an American study conducted by the university of Washington.

The findings were published in the Archives of Pediatric and Adolescent Medicine. The study states that high rates of television viewing could be associated with poor educational achievement through several mechanisms. Perhaps the most obvious of these is by displacement of learning activities.

For example, time spent watching television among sixth- and seventh-grade students in the US has been found to be inversely correlated with reading and homework. Television viewing in young children has also been associated with attention and behavioral problems, which in turn are likely to have an adverse impact on school performance. Whether or not excessive television viewing is a direct cause of poor educational achievement, the findings indicate that the majority of television viewing is unlikely to have an educational benefit.

The researchers analysed standardised tests and television viewing habits of more than 1,700 children monitored as part of a long-term national study.

Based on tests taken by children ages 6 to 7, the study found that those who averaged more than two hours of TV a day when they were younger than 3 scored lower in reading and short-term memory. There were no significant interactions between sex and television viewing or between the socio economic status and television viewing for either educational outcome. There was an interaction between television viewing hours and IQ for attaining a university degree that was of borderline statistical significance

The study examined the associations between the mean hours of television viewing per weeknight and failure to attain an educational qualification by 26 years of age and between television viewing and attainment of a university degree by 26 years of age. This was done by using logistic regression analyses adjusted for sex and IQ. Risk ratios (RRs) and 95 per centy confidence intervals (CIs) were estimated for each outcome using log-binomial regression models.

Further regression models examined the association between television viewing and educational outcomes, with additional adjustment for childhood socioeconomic status and childhood behavioural problems.