MANUAL ASYMMETRIES AND THE EFFECTS OF TASK COMPLEXITY ON SIMPLE REACTION TIME

Some manual asymmetries studies have pointed out that left hand enjoys an advantage over right hand in reaction time (RT), attributing this advantage to the right hemisphere specialization for localization of targets and limbs, prior to the organization of the movement. Few studies investigated the relation between manual asymmetry and task complexity on RT. Therefore, the aim of the present study was to verify the effect of task complexity on motor programming in both hands through simple reaction time (SRT) measure. Thirty two right-handed participants (age ranging from 18 to 35 years) were randomly assigned for one of two experiments (n=16): Exp1 ?SRT task with different effector complexities; Exp2 ? two SRT task with different spatial complexities. Exp 1 consisted of performing two tasks: 1) simple task, which consisted of release a push-button as quickly as possible after a visual stimulus; 2) complex task, which consisted of releasing a push-button as quickly as possible after a visual stimuli and positioning a tennis ball into two recipients in the ipsilateral hand workspace. Exp2 also consisted of performing two tasks: 1) simple task, which consisted of releasing a push-button as quickly as possible after a visual stimuli and positioning a tennis ball into two recipients in the ipsilateral hand workspace; 2) complex task, which consisted of performing the same task but in contralateral hand workspace. In all conditions both hands performed the tasks. Data analysis was carried out through ANOVA two-way and Tukey Post-hoc. In Exp1, the analysis did not show significant difference for Hands, as well as for Hands x Complexity interaction (p>0.05), but detected significant difference for Complexity [F(1,30)=16.60, p 0.05). However, it was detected a marginal difference for Complexity [F(1,30)=3.34, p=0.07] indicating a tendency to a lower SRT for both hands in the right workspace compared with the left workspace. These results did not indicate manual asymmetries on SRT in function of the task complexity. Further research is suggested to investigate manual asymmetries and the effects of task complexity on choice reaction time.