Reaction time and hand dominance

Abstract

In most individuals, there is a significant difference in hand dominance and this suggests that  sensorimotor tasks, such as reaction time, would demonstrate a difference in performance tasks conducted with dominant versus non-dominant hand. In this study, comparisons were made between the reaction time of the dominant to the nondominant hand, the reaction time of the male participants to that of the female participants, the reaction time variability of the dominant hand of the male participants to that of the dominant hand of female participants, and finally the reaction time variability of the nondominant hand of the male participants to that of the female participants. The study was conducted virtually with participants performing a set of instructions emailed to them. The results demonstrated that the reaction time of the dominant hand was faster than that of the nondominant hand in all participants, the reaction time of the male participants was faster than that of the female participants, the reaction time variability of the dominant hand was higher in male than in female participants, and lastly, the reaction time variability of the nondominant hand was lower for the male than in the female participants.

Citation

Chouamo AK, Griego S, Lopez FAS. (2020). Reaction time and hand dominance. Journal of Science and Medicine; 3(Special Issue):1-7. https://doi.org/10.37714/josam.v2i4.66.

Introduction

It is widely known that most humans multitask and perform movements better with one hand than the other. Up to 90% of humans are right-handed, some are left-handed, and an indeterminate number of people are ambidextrous (can use both hands equally) [1]. Historically, decades ago, and in some cultures, right handed individuals were associated with positive values and the left handed people were associated with negative ones [2]. This led to the disparagement of left-handed people, and they were often forced to switch hand use. These myths were dispelled in 1960, when it was discovered that speech was based predominantly in the left hemisphere of the brain. Currently, it is well known that hand dominance is not a conscious decision.

Studies have shown that genes affect handedness. The PCSK6 and the LRRTMI genes are associated with the likelihood of being right handed and left handed respectively [3]. Genetics are not the only factors that contribute to handedness. Another factor is the neural activity that happens in the left and right hemispheres of the brain, which tends to influence whether the left or right hand is dominant to the other hand [4].

Reaction Time (RT) in relationship to hand dominance has been assessed by a number of researchers. Vidal et al [5] and Shen and Franz [6] used a simple ipsilateral visual stimulus and reported that in right-handed individuals key pressing was faster by the right hand, which was the dominant hand for all of the subjects, than by the left hand using simple reaction time tasks. However, Rabbitt [7] and Di Stefano et al. [8] in their work reported that both hands react with the same latency for a finger-extension response in a simple task.

One of the ways to evaluate the reaction time in humans is by using the Brain Gauge [9] (shown in Figure 1). This device has been described and used in multiple studies for assessing reaction time [9-11]. The purpose of this paper is to investigate the difference in a reaction time task with the dominant versus nondominant hand. Based on a study conducted in 2006 by Heuer [12], it is hypothesized that the reaction time for the dominant hand will be faster (shorter) than that of the nondominant hand. In addition, based on the experimental finding by Shimoyama [13] that men react faster than women do, another hypothesis is that the reaction time for males will be faster than that for females.

Figure 1.Two-point vibrotactile stimulator (the Brain Gauge; Cortical Metrics; Chapel Hill, NC).

Materials and methods

Subjects

Twenty-nine healthy individuals (15 males, 14 females) participated in this study. Participants were aged 20 to 39 years old. Twenty-seven were right handed and the remaining two were left handed subjects.

Apparatus

The age, gender and hand dominance of the participants were collected through a survey prior to conducting the experiment. The experiment involved having the subject seating down in front of a computer connected to the Brain Gauge hardware. This Brain Gauge hardware is a two-point vibro-tactile stimulator (the Brain Gauge by Cortical Metrics, Carrboro, NC), which was used to deliver stimuli to the tips of digits 2 and 3 according to the signal that the Brain Gauge software program sent to the device. The device had tips that are controlled by the computer, which delivers sinusoidal vibrotactile stimulation. The second, index finger, and third, middle, digit were chosen as test sites because of the convenience of the location of those fingers and to make the protocol more comfortable for the user.

The computer monitor showed cues useful for the experiment. The cues indicated when the stimuli would be delivered and when the subjects had to respond. The Brain Gauge program provided three training trials prior to the trials used for collection, which helped the subjects to get familiar with the experiment.

For this experiment, the subjects were divided into two groups based on whether their identifying number (also known as subject ID; the subject ID is a randomized number that de-identifies participants) was even or odd. Each group had a different set up. The main difference between the two setups was that the subjects that had an even subject ID began the experiment with their dominant hand first, while the subjects that had an odd subject ID began the experiment with their nondominant hand first.

The participants whose subject ID was even began the experiment with their dominant hand, followed by the nondominant, while those whose subject ID was odd began the experiment with their non-dominant, followed by the dominant. This was done in order to factor out the effect of fatigue on the results we obtain. The experimental tasks that the subjects had to complete were the tactile reaction time task for both hands.

For the tactile reaction time task, the subjects felt a vibration stimulus on digit 3 and had to respond with digit 2 on the Brain Gauge’s button that was not stimulated.

Results

This experiment yielded the following results. As can be seen on Figures 2‒3, the reaction time was shorter (faster) for males than for females. In addition, as it can be observed in Figure 6, the reaction time of the dominant hand was also faster compared to the nondominant hand. Moreover, the data shows that the reaction time variability for the dominant hand was lower in males than in females as it can be seen in Figure 4. Meanwhile, for the nondominant hands, the reaction time variability was faster in the female participants than in the male participants as it can be seen in Figure 5.

Collected data shows that the average of the dominant hand’s reaction time is 237 msec, while the average of the nondominant hand’s reaction time is 270 msec. In addition, the average of the dominant hand’s reaction time variability is 18.96 msec, while it is 22.59 msec for the nondominant hand. While comparing the reaction times between genders, collected data showed that the average reaction time of the dominant hand for females and males are 251.2 msec and 224.7 msec, respectively. Likewise, it showed that the average nondominant hand reaction time for females and males are 291.7 msec and 249.7 msec, respectively. In addition, the data showed that the average dominant hand reaction time variability for females is 19.4 msec, while it is 18.5 msec for males. Moreover, it showed that the average nondominant hand reaction time variability for females and males are 20.0 msec and 25.02 msec respectively.

A two sample (two-tailed) T-test, assuming equal variances, was used to compare the reaction times between males and females. The T-test performed gave a p-value of 0.0042, which is much lower than the significant value of 0.05. This means that there is a significant difference between the averages of the two independent sets.

The individual differences between dominant and non-dominant hand in the study can be viewed in tables displayed in Tables 1,2.

Figure 2.Dominant Hand Reaction Time for Females vs. Males. Comparison of the average dominant hand reaction times between genders. The mean reaction times were 26.5 ms shorter in men than in women (251.2 ms vs 224.7 ms, respectively).

Figure 3.Nondominant Hand Reaction Time for Females vs. Males. Comparison of the average nondominant hand reaction times between genders. The mean reaction times were 42 ms shorter in men than in women (249.7 ms vs 291.7 ms, respectively).

Figure 4.Dominant Hand Reaction Time Variability for Females vs. Males. Comparison of the average dominant hand reaction time variabilities between genders. Females' results were higher and more variable on average by 0.9 ms than males (19.4 ms vs 18.5 ms, respectively).

Figure 5.Nondominant Hand Reaction Time Variability for Females vs. Males. Comparison of the average dominant hand reaction time variabilities between genders. Males' results were higher and more variable on average by 5.02 ms than females (20 ms vs 25.02 ms, respectively).

Figure 6.Reaction Time of the Dominant and Nondominant Hand. The dominant hand mean reaction times were 33 ms shorter in comparison to the nondominant hand (237 ms vs 270 ms, respectively).

Figure 7.Reaction Time Variabilities of the Dominant and Nondominant Hand. The dominant hand mean reaction time variabilities were lower and more variable on average by 3.63 ms than the nondominant hand (18.96 ms vs 22.59 ms, respectively).

Table 1.Table Showing the Reaction Time Difference of the Dominant and Nondominant Hand for Even Subjects

Even Subject ID (Dominant Hand First)	0028	0012	0002	0010	0040	0060	0024	0008	0030	0050	0016	0046	0020	0044	0064
Dominant Hand Reaction Time (msec)	262.4	186.4	196.6	275.8	255.6	185	254	219.6	224.6	244.2	217.2	205	240.4	190.6	213.2
Nondominant Hand Reaction Time (msec)	326.6	257.2	204	307.4	344.4	206	270.6	221.6	240.8	260.2	378	206.8	285.4	204.4	229
Reaction Time Difference between Hands (msec)	64.2	70.8	7.4	31.6	88.8	21	16.6	2	16.2	16	160.8	1.8	45	13.8	15.8

Table 2.Table Showing the Reaction Time Difference of the Dominant and Nondominant Hand for Odd Subjects

Odd Subject ID (Nondominant Hand First)	0041	0021	0049	0015	0055	0029	0011	0033	0025	0047	0057	0063	0059	0023
Dominant Hand Reaction Time (msec)	225.8	273.6	305.6	227.6	250	313.8	340.8	231.4	220.8	215.6	202	250.6	210	249.2
Nondominant Hand Reaction Time (msec)	229.4	277.2	333	318.2	264.8	350.6	343	239.4	258.6	288	244.8	260.4	227.6	252.6
Reaction Time Difference between Hands (msec)	3.6	3.6	27.4	90.6	14.8	36.8	2.2	8	37.8	72.4	42.8	9.8	17.6	3.4

Discussion

The main findings of this study are that the reaction time of the dominant hand was lower than that of the nondominant hand in all participants, the reaction time of the male participants was quicker than that of the female participants, the reaction time variability of the dominant hand was lower in male than in female participants, and lastly, the reaction time variability of the nondominant hand was higher for the male than in the female participants.

Nobel et al. reported in his study that reaction time (RT) in males is faster than in females of almost every age group, which was concluded in that study as a disadvantage for females and that this disadvantage was not reduced by practice [14]. The authors of that study concluded that this was because women were more cautious and tended to avoid errors more as compared to men, hence are found to be slower in their reactions, thereby making men faster [14]. In the same study, the Nobel et al. also declared that the muscle contraction times for both genders were similar. Nevertheless, women had a lesser error rate given that they have the tendency to inhibit their PVT (Psychomotor Vigilance Task) response better than men do. The behavioral responses reflect a high level of motivation for both males and females. Although the authors of this paper do not agree with the conclusion of women being more “cautious” than men, the results of that study were consistent with the results of this study.

Studies done by Misra et al. [15], Shelton and Kumar [16], and Nikam and Gadkari [17] all reported similar findings and supported the suggested hypothesis that females have slower reaction times than males. Figure 2 demonstrated that the results of this study agree with the aforementioned research findings and indicates that males have faster reaction times when compared to females for both the reaction time and the reaction time variability tests. The data from a study completed by Serrien and her colleagues showed that the preferred hand reacted more quickly than the non-preferred hand, which suggested “an increased response readiness due to hand preference” [18].

Another finding was that the reaction time and reaction time variabilities of the dominant hand were faster than that of the nondominant hand as it can be seen in Figures 6‒7 respectively. The neurons that carry messages between that of the hand and brain are faster for the dominant hand given that it is used more often. One can improve their motor skills by running the same messages repeatedly along the same pathway. This justifies the scientific expression that says, “Practice makes perfect”. This idea is not only used to compare the reaction time of both hands, it is also used to compare their reaction time variabilities [19].

A final comparison that was made was the observation of individual differences. This was accomplished by subtracting the reaction time of the dominant hand from that of the nondominant hand. All of the values obtained were positive as it can be seen in Tables 1,2. This demonstrates that the reaction time of the nondominant hand was higher (slower) than that of the dominant hand. In other words, the individual data, on a case-by-case basis, confirms the first hypothesis. In addition, the Two-Sample T-Test determined that a statistically significant difference exists between the averages of two independent sets (Males vs. Females), and also supports the proposed hypothesis.

Conclusions

This study led to several findings. First, the reaction time for the dominant hand was faster than that of the nondominant hand for all participants, thus confirming the first proposed hypothesis. Second, the data supported the second hypothesis, which stated that the male participants had a faster reaction time than the females. Another finding was that the reaction time variability for the dominant hand was lower in males than in females, while for the nondominant hand, the reaction time variability was lower in female’s participants than in male participants.