There's a fair amount of research on TV and academic achievement, though it's not all conclusive. Some also relate TV watching to low feelings of 'well-being', which is interesting as regards how many Mumsnetters said they put on the TV to quiet down a shouty internal monologue, or the stop feeling alone in the house.
This is just an online magazine, but it does credit some studies:
www.endalldisease.com/studies-show-television-decreases-iq-creativity-academic-achievement-and-damages-the-brain/
•Reported in the Journal of Genetic Psychology was the finding that children’s television viewing ‘resulted in an eventual decrease in their academic achievement.’ (1)
•Then, in a 2005 study, other scientists confirmed ‘deleterious effects’ on mathematics ability, reading recognition and understanding later in childhood. Not only does television viewing displace both playful and educational activities, Scientists suspect this harm is due to visual and auditory output actually damaging the child’s developing brain. (2)
•Another study found that children ages eight and nine who have televisions in their bedrooms achieved the worst scores in school achievement tests. (3)
•A brand new 26-year study which tracked kids from birth up until the age 26 has concluded ‘television viewing in childhood and adolescence is associated with poor educational achievement by 26 years of age, and may have long-lasting adverse consequences for educational achievement and subsequent socioeconomic status and well-being.’ The doctors found significant long-term damage occurred even at so-called ‘modest levels’ of television viewing: between one and two hours per day. (4)
1 – Shin, N. ‘Exploring pathways from television viewing to academic achievement in school age children’, J. Genetic Psychology, December 2004; 165 (4) 267-81
2 – Zimmerman F.J., Christakis D.A. ‘Children’s television viewing and cognitive outcomes: a longitudinal analysis’, Archives of Pediatric Medicine, 2005; 159:619-625
3 – Borzekowski D.L.G., Robinson T.N. ‘ The remote, the mouse, and the no. 2 pencil: the household media environment and academic achievement among third grade students’, Archives of Pediatric Medicine, 2005; 159:607-613
4 – Hancox R.J. et al. ‘Association of television viewing during childhood with poor educational achievement’, Archives of Pediatric Medicine, 2005; 159: 614-618