Mean and standard deviation of simple reaction time and four-choice reaction time were used to assess speed and variability of simple information processing. The tasks were administered using a stand-alone shallow rectangular box constructed for the UK Health and Lifestyle Survey [59]. This was described in detail and illustrated previously [60]. On the top face there is a high-contrast liquid crystal display (LCD) screen. There are five response keys arranged in a shallow arc and numbered, from left to right, 1, 2, 0, 3, 4. In the simple reaction time test there are 8 practice trials and 20 test trials. The participant rests the second finger of the preferred hand on the 0 key. After a zero appears on the LCD screen the participant presses the key as fast as possible. The mean and standard deviation of the 20 simple reaction time trials are calculated. The four-choice reaction time test has 8 practice trials and 40 test trials. The participant rests the second and third fingers of the left and right hands on, respectively, the keys marked 1, 2, 3,
