Physical effort causes human eye to dilate

New Scientist : Previous studies have shown that mental effort in humans can cause their pupils to dilate. Now a recent study shows that pupils dilate with physical effort as well. Alexandre Zenon at the Catholic University of Louvain in Belgium and colleagues tested the theory by having volunteers squeeze a device that measured their grip strength. Then they used various tests to also determine how much effort participants thought they were exerting. The researchers found that dilated pupils resulted more from perceived effort than from actual effort. They then located the area of the brain responsible for the perceived effort and discovered that if they blocked that area, the subjects reported that the same tasks seemed easier, even though they had exerted the same effort as before. Whether that finding has any practical use remains to be seen.