 The purpose is to conduct a randomized, single-masked crossover study to determine if acute consumption of a commercially available, highly palatable dark chocolate bar can improve visual performance. Vision testing will include multiple measures of contrast and color perception, reaction time, effects of distraction on visual performance during simulated hands-free phone calls, simulated marksmanship, as well as multiple, objective electro-diagnostic tests including standard and color visual-evoked potentials and various types of electro-retinograms to assess visual pathway function. 