COMPARATIVE EFFECT OF CAFFEINE PER SE AND A CAFFEINE BEVERAGE (COFFEE) UPON THE REACTION TIME IN NORMAL YOUNG ADULTS

¹ From the Department of Biology, Long Island University, Brooklyn, New York

Coffee, containing an equivalent amount of caffeine, produced parallel results to capsulated caffeine, but to a lesser degree in most individuals. The performance of the test, involving the response to a visual stimulus requiring a mental decision and a muscular movement of definite precision (choice of three possibilities), was enacted within a shorter period after the consumption of caffeine or coffee, provided the dose exceeded 3 mgm. per kilogram of body weight. The reduction effects were not impaired by subsequent increased reaction time within the three-hour period recorded.

The reaction time in man, as measured by the simplified apparatus for determining intervals of one one-hundred twentieth second, was not affected by single doses of caffeine unless the dosage exceeded 3.0 mgm. per kilogram of body weight. Dosages between 3.0 and 4.0 mgm. per kilogram produced variable effects, while the administration of 5.0 mgm. per kilogram or above always produced a decrease in the reaction time over at least a three-hour period.

In the majority of the subjects when the dosage was sufficient to produce any recordable effect, a slight reduction time was observed within a period of thirty minutes after the consumption of either caffeine or coffee. Generally, the maximum effect was noted within the two-to-two-and-one-half-hour period. The maximum reduction in time was usually greater with pure caffeine than with an equivalent amount in the form of the coffee beverage.

Twenty-four hours after the consumption of caffeine in the pure state or in the beverage form, no significant effect upon reaction time could be noted in any subject regardless of the dosage used within the range of 2.9 to 5.6 mgm. per kilogram employed in this experimental series.