The effect of water consumption on cognitive performance

Dehydration has negative effects on cognitive performance and mood in both adults and children. There is some evidence that having a drink of water results in improved cognition in thirsty adults. Recent studies in children have shown that drinking additional water is associated with better performance on tests of memory and attention. Performance on letter cancellation, a test of visual attention, seems particularly sensitive to hydration. The present study sought to investigate whether water consumption particularly affects the speeded element of the task. Eighteen 12- and 13-year-old children took part on two occasions; on one they were offered 500 ml water and on the other they were not. They completed a thirst scale and were tested on a speeded and non-speeded letter cancellation task (in which time taken was surreptitiously recorded) and a fingertip tapping task (to assess motor performance). Children rated themselves as less thirsty on the occasion on which they had a drink (p=0.006). In the case of speeded letter cancellation, they performed faster on the occasion on which they had a drink compared to the no drink occasion (p=0.041). For both non-speeded letter cancellation and fingertip tapping, there was no difference in performance between water conditions. These results suggest that the speeded component of letter cancellation is hydration sensitive. Further research is necessary to delineate the nature of the water consumption effect on visual attention.