THE EFFECT OF CAFFEINE ON REACTION TIME, HAND STEADINESS, AND SPECIFIC PHYSIOLOGICAL VARIABLES

450 The problem of this study was to analyze the effect of caffeine on heart rate, blood pressure, reaction time, and hand steadiness. Subjects (N = 20) were classified as high-caffeine users or low-caffeine users. Heart rate, blood pressure, reaction time, and hand steadiness were measured. Subjects then consumed 24 oz of coffee containing 345 mg of caffeine in a 5-min period. Dependent variables were measured again at 30, 60, and 90 min after caffeine administration. No significant differences (p > .05) were found between the groups, high- and low-caffeine users, for heart rate, systolic blood pressure, diastolic blood pressure, reaction time, or hand steadiness. Significant differences (p < .05) were found among test time means for all variables. A significant (p < .05) first order interaction effect, groups by test times, occurred for reaction time. The researchers concluded that caffeine (a) did not increase heart rate, (b) increased systolic blood pressure 60 min after caffeine intake, (c) increased diastolic blood pressure at 30 and 60 min after caffeine intake, (d) decreased reaction time for the high-caffeine-use group, and (e) had no effect on hand steadiness. Recommendations for further study included designing the study to measure baseline heart rate and blood pressure prior to caffeine administration and using a balanced placebo design to see if regular caffeine users respond due to caffeine or to expectancy.