Effects of drugs, age and illumination on response speed of squirrel monkeys

Four young (2 1/2 years) and four older (over 10 years) squirrel monkeys were used to study age differences in the effects of d-amphetamine, methylphenidate and illumination on response speed. Although young monkeys were faster than the old monkeys, only the older monkeys showed an illumination effect. Both d-amphetamine and methylphenidate slowed response speed but only in the older monkeys showed an illumination illumination was present. These results suggest that older, mature squirrel monkeys are more sensitive to the effects of d-amphetamine, methylphenidate and illumination than young squirrel monkeys.