... speed was recognised in a classic study by Birren, Butler, Greenhouse, and Yarrow (63). They used a total of 47 men between the ages of 65 and 91 who were healthy, according to a clinical examination. They were then split into two groups, group 1, were in good health and group 2, and were without obvious symptoms of disease. This small difference turned out to be very important in understanding the real connection between age and information processing. It was found that intelligence measures that demanded fast responses were flawed for both groups and old adults were significantly slower in psychomotor speed than young adults. This data insinuates that age slows down the reaction time regardless of the health, muscle used and sensory modality of an individual. Therefore, because this change occurred in both groups, it can be assumed that it is related to age rather that disease. Many researchers ...

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