Researchers highlighted how a grid of light bulbs, where one differs in color, was used to test visual acuity. Participants were challenged to find the odd grey bulb among turquoise ones in just 3 seconds. Such optical illusions help improve concentration and cognitive function while providing an engaging mental exercise.Researchers highlighted how a grid of light bulbs, where one differs in color, was used to test visual acuity. Participants were challenged to find the odd grey bulb among turquoise ones in just 3 seconds. Such optical illusions help improve concentration and cognitive function while providing an engaging mental exercise.