The more television infants and toddlers watch, the more likely they are to have trouble paying attention and concentrating during their early school year. Although there has been other research on how many hours of TV very young kids watch, this is the first study on how early viewing might affect attention span. Every added hour of watching TV increased a child's odds of having attention problems by about 10 percent. Kids watching about three hours a day were 30 percent more likely to have attention trouble than those viewing no TV. Animal studies show that stimulating environments can change young brains. The rapid-fire stimulation of TV might do the same.
Kids watch far too much TV, this is a no-brainer, literally. My recommendation is to minimize the TV to no more than a few hours per WEEK, as short attention spans is only the beginning of the problem with TV. Here are some of the other negatives of kids watching TV:
Pediatrics April 2004;113(4):708-713