Poor study design for such sweeping claims. Correlation is not causation. Plethora of reasons people who were later measured with small brain sizes may have been heavy TV watchers earlier in life.
Perhaps people who already have small brains watch more TV. Or perhaps exercise is important to brain size, and people who can’t exercise watch more TV. Or maybe not watching TV, and doing other things with your time, grows your brain size.
Perhaps people who already have small brains watch more TV. Or perhaps exercise is important to brain size, and people who can’t exercise watch more TV. Or maybe not watching TV, and doing other things with your time, grows your brain size.