Investigating Response Time of the Dominant and
Non-dominant Hands
Introduction
The nervous system enables one’s body to react to various external events or changes in the
immediate surrounding environment, known as stimuli. One’s body may react deliberately
and are conscious decisions. Such voluntary responses include kicking a ball coming your
way. Others are a rapid, automatic action; take for example the radial muscles in one’s iris
contracting to enable the dilation of the pupil, by way of allowing more light to enter onto the
retina when light intensity is fairly low. These are called reflexes, and do not require any
thinking behind it. Catching a dropped object, such as in this investigation requires a degree
of reflex action, as though your brain is aware of the incoming stimuli, you yourself only
consciously register what is happening after the electrical impulses have reached the
muscles.
Research Question
How does the time of response to a visual stimulus of the dominant hand differ from the nondominant hand?
Hypothesis
I predict that the response time of the dominant hand to a visual stimulus of a dropped ruler
will be substantially faster in comparison to that of the non-dominant hand. Hence, the
distance the ruler drops from a fixed height will be noticeably smaller when the dominant
hand is set to catch it. This is because the dominant hand is used more frequently and
therefore possesses greater dexterity in contrast to one’s non-dominant hand. Moreover,
motor skills in the preferred hand tend to be more enhanced from repeated transmission of
electrical impulses along neurones from the receptor cells, to the central nervous system
(CNS) and back to the effector in carrying out day-to-day actions. Over time this recurrent
process of communication, otherwise known as coordination, occurs at a faster rate due to
regular practice.
Independent Variable
Dominance of hand: There is only 2 ways in which to vary this variable: switching hands to
catch the ruler after 25 times each, first from the dominant hand, to be followed by the nondominant.
Dependent Variable
Time of response to catch ruler: To collect this particular type of data, I measured the
distance the ruler had dropped (in centimetres) from a fixed height before the allocated hand
caught it. I then proceeded to calculate the response time using the following equation:
𝑡𝑖𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑝𝑜𝑛𝑠𝑒 (𝑖𝑛 𝑠𝑒𝑐𝑜𝑛𝑑𝑠) = √
2×𝑑
980
where d is the distance (in centimetres) the ruler had dropped before it was caught. To
increase my results’ reliability, I performed 25 trials per hand, and computed the mean time
of response for my dominant and non-dominant hands in catching a falling ruler. I also
referred to a predetermined graph (look at method) assigned me at the beginning of my
investigation to ensure my response time calculations were accurate.
Control Variables
Height From Which Ruler
Was Dropped
(cm)
Distance of Thumb and
Forefinger from the Ruler
(cm)
Position of Eye in
relation to the Ruler
Warning of
Imminent Stimulus
Level of
Caffeine (mg)
Apparatus

A metric ruler of 30 cm
The height from which my partner was tasked to drop the ruler
was required to be a fixed distance from my waiting fingers. To
accomplish this, I rested my arm along the bench top, as a
reference point that will never fluctuate throughout the
experiment as the bench is stationary, and therefore my hand
level will not change. My partner then proceeded to hold and
suspend the ruler so that the zero mark was level and
perpendicular to my hand. This way, the ruler will remain a 30
cm distance from my prepared hand throughout.
It is essential that the gap between the thumb and forefinger
when enclosing the bottom edge/zero mark of the ruler is
approximately 2 cm apart, with the ruler an equal distance
from them both. This is slightly more difficult to regulate, as
fingers held in that specific position tend to quiver slightly in
anticipation of a falling object. This can cause the distance
between the fingers and the ruler to lessen, effectively
minimizing the distance required to grasp the dropped ruler
and lower the reaction time, and vice versa if the distance
increases to more than 2 cm.
The angle/distance of my eye to the ruler must not vary
between trials, or during the switching of hands from the
dominant to the non-dominant, as the visual stimulus of a ruler
falling perceived by direct vision will produce a faster reaction
time as opposed to when detected with peripheral vision. Cone
cells from when one is looking directly at any stimuli will
identify any changes faster than by rod cells around the eye’s
periphery, prompting faster reflex actions. To ensure a
constant eye position, I sat on the same chair throughout the
investigation, a fixed height from the bench top where the
ruler’s zero mark rests.
It is necessary for my partner holding the ruler upright to warn
me by saying “Ready”, and dropping the ruler without any
further warning. She must also be careful to do so within a five
second timeframe, as it is difficult to maintain concentration
or muscular tension at the highest degree for any time longer
than a few seconds.
As a stimulant drug, it is necessary to ensure that caffeine is
not ingested in between trials, or before switching from the
dominant hand to the non-dominant. The quantity of caffeine
in coffee, for example, is capable of decreasing one’s reaction
time to any form of stimulus, be it visual, auditory or touch, and
strengthen resistance to distraction that can inhibit the time it
takes to response. Moreover, the minimal lag time required for
caffeine to take effect after consumption will also cause a
greater portion of the data recordings to be affected, leading
to an unbalanced overall results table.




Chair / stool
Table / bench top
Pencil
Measuring tape
Method
I.
Work in pairs. Position your partner by a bench, whilst holding a ruler between his/her
thumb and forefinger, ensuring that the bottom edge or the zero mark hangs level with
the bench top.
II.
Sit yourself on a chair and rest your dominant arm
(on its side) flat across the bench top, aligning your
wrist along the bench’s edge, so as to not allow your
hand to be in direct contact with the bench’s
surface.
III.
Enclose the zero mark of the ruler with your thumb
and forefinger on either side of it, ensuring the two
fingers are an approximate 2 cm distance apart,
with the ruler directly in the center between them.
IV.
Your partner holding the ruler will say, “Ready” and
drop it at any given moment within 5 seconds. Your
task is to catch the ruler by grasping it with your readied thumb and forefinger.
V.
Record the distance the ruler dropped (in centimetres) in a table by noting the mark at
which the top of your forefinger pinched the ruler.
VI.
Reset the arrangement of your exercise according to steps I, II and III. Proceed to then
perform steps IV and V again to receive 25 trials worth of measurements (for your
dominant hand to catch a ruler).
VII.
Switch to your non-dominant hand and repeat step VI.
VIII.
Once all the readings have been taken for both hands, calculate the mean distance
dropped by the ruler before the respective hand caught it, by adding all the values
together to then be divided by 25.
IX.
Compute the reaction time of each hand in catching the ruler for all 50 trials (25 each)
based on the following equation:
𝑡𝑖𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑝𝑜𝑛𝑠𝑒 (𝑖𝑛 𝑠𝑒𝑐𝑜𝑛𝑑𝑠) = √
2×𝑑
980
where d equals to the distance dropped by ruler (in cm) before caught. Calculate the
mean response time for the dominant and non-dominant hand by adding all the values
together before dividing the answer by 25. Record this in your table.
To ensure your calculations are accurate, refer the mean response time determined by
the equation with the preset graph below, using the mean value calculated in step VIII
as your distance dropped by ruler (in cm).
Sample Computation
 TO CALCULATE TIME OF RESPONSE (in seconds)
SUBJECT A: TRIAL 25 OF DOMINANT HAND
distance dropped by ruler before caught (cm): 15.5
2×𝑑
𝑡𝑖𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑝𝑜𝑛𝑠𝑒 (𝑖𝑛 𝑠𝑒𝑐𝑜𝑛𝑑𝑠) = √
980
d = distance dropped by ruler
2 × 𝟏𝟓. 𝟓
𝑡𝑖𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑝𝑜𝑛𝑠𝑒 (𝑖𝑛 𝑠𝑒𝑐𝑜𝑛𝑑𝑠) 𝑓𝑜𝑟 𝑇𝑅𝐼𝐴𝐿 25 = √
980
= 0.18
 TO CALCULATE MEAN RESPONSE TIME (in seconds) of SUBJECT A’s DOMINANT
HAND
=
=
𝑠𝑢𝑚 𝑜𝑓 𝑎𝑙𝑙 𝑣𝑎𝑙𝑢𝑒𝑠
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑟𝑖𝑎𝑙𝑠
0.17 + 0.16 + 0.16 + 0.17 + 0.12+. . . +0.18
25
= 𝟎. 𝟏𝟓 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
Further Calculations
 TO CALCULATE SPEED AT WHICH NERVE IMPULSE TRAVELLED (cm/s) in SUBJECT
A’s DOMINANT HAND
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑛𝑒𝑟𝑣𝑒 𝑖𝑚𝑝𝑢𝑙𝑠𝑒 (𝑐𝑚⁄𝑠) =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑒𝑦𝑒 𝑡𝑜 𝑓𝑜𝑟𝑒𝑓𝑖𝑛𝑔𝑒𝑟 (𝑐𝑚)
𝑚𝑒𝑎𝑛 𝑡𝑖𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑝𝑜𝑛𝑠𝑒 𝑡𝑜 𝑐𝑎𝑡𝑐ℎ 𝑡ℎ𝑒 𝑟𝑢𝑙𝑒𝑟 (seconds)
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑛𝑒𝑟𝑣𝑒 𝑖𝑚𝑝𝑢𝑙𝑠𝑒 (𝑐𝑚⁄𝑠) =
99 𝑐𝑚
0.15 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
= 𝟔𝟔𝟎
 TO CALCULATE SPEED AT WHICH NERVE IMPULSE TRAVELLED (cm/s) in SUBJECT
A’s NON – DOMINANT HAND
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑛𝑒𝑟𝑣𝑒 𝑖𝑚𝑝𝑢𝑙𝑠𝑒 (𝑐𝑚⁄𝑠) =
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑒𝑦𝑒 𝑡𝑜 𝑓𝑜𝑟𝑒𝑓𝑖𝑛𝑔𝑒𝑟 (𝑐𝑚)
𝑚𝑒𝑎𝑛 𝑡𝑖𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑝𝑜𝑛𝑠𝑒 𝑡𝑜 𝑐𝑎𝑡𝑐ℎ 𝑡ℎ𝑒 𝑟𝑢𝑙𝑒𝑟 (seconds)
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑛𝑒𝑟𝑣𝑒 𝑖𝑚𝑝𝑢𝑙𝑠𝑒 (𝑐𝑚⁄𝑠) =
101 𝑐𝑚
0.18 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
= 𝟓𝟔𝟏
Conclusion
The response time of the dominant hand to a visual stimulus of a dropped ruler is
significantly faster than that of the non-dominant hand. This is illustrated clearly by the
column chart wherein the three bars indicating the mean response times of the class, subject
A and subject B’s dominant hand are noticeably smaller in height than their respective
counterparts in the non-dominant hand category, demonstrating a substantial difference
when it comes to how fast both hands react in contrast with each other. All three sets of data
support my hypothesis.
The neural pathway undertaken by electrical impulses to catch a falling ruler in this
investigation is as follows:
stimulus (ruler drops)  (sensory) receptor cells in eyes  sensory neurones  the central
nervous system (specifically the spinal cord)  motor neurones  effector (hand/finger
muscles)  response (contraction of hand/finger muscles to catch ruler)
The transmission of nerve impulses according to the above stated route, occurs at a faster
rate in the dominant hand in comparison to the non-dominant, due to the regular handling of
day-to-day actions with the preferred hand, inducing more dexterity from frequent practice
and accounting for faster reaction times. This is proven by subject A’s (dominant hand) mean
response time of 0.15 seconds producing a 660 cm/s reflex speed, 18% faster than the nondominant hand’s 561 cm/s, whose mean reaction time was a lengthier 0.18 seconds.
As seen from the results table and the column chart, subject B has a considerably more
enhanced dominant hand compared to her non-dominant, with a 36% increase in reaction
time when she employs the use of her preferred hand. This in contrast to subject A, whose
reaction time when catching the ruler with her dominant hand is only 20% faster as to when
she switches to her non-dominant, indicates that there might be some external factor that
affects the time it takes to respond to a visual stimulus. It is interesting to note that subject B
is a student particularly active in the field of sport, whereas subject A is more of an introvert.
This circumstance possibly contributes to subject B’s more prominent difference between
her preferred and less preferred hand’s response times, as it is very rare that the nondominant limb is used in sport (for example, when throwing or catching a ball). The avid
participation in sport would also account for subject B’s faster response time in the dominant
hand than subject A’s.
It wasn’t particularly ideal to compare the class’s mean response time for their dominant and
non-dominant hands with subjects A’s and B’s. This is because the number of trials performed
by each student varies between every pair, leading to a variable level of reliability when
collecting the results in to compute a mean. And so, plotting the class value against subjects
A and B (who both performed 25 trials per hand) would not make for a fair comparison.
Several of the distances the ruler dropped before the allocated hand caught it were
anomalous results (highlighted red in the data table). To prevent the mean time of response
being affected, I plotted a separate column chart to identify the range in which most of the
points stayed within, and repeated any that went beyond that zone. Through this method, I
eliminated any anomalies from my results table. This however produces a certain degree of
inconsistency in my values, as a portion of my recordings is not part of the raw data.
Evaluation
 A strength of my investigation was that both subjects (myself and my partner) performed
25 trials for both our dominant and non-dominant hands. This enabled us to compute a
mean reaction time in response to a visual stimulus, consequently improving the
reliability of our results. However, the drawback to this was that each hand was receiving
more practice the longer the investigation wore on with the increasing number of trials.
Therefore, we were able to adapt to the nature of the impending stimulus, and anticipate
it with more sureness. The motor skills of our hands improved the more times we
performed the exercise, which would lead to a decline in our overall mean response times.
To rectify this, and still maintain a fairly high level of reliability, we should aim to perform
between 10 to 15 trials, as any number greater than that will aid us in enhancing our
reaction times, instead of examining them to compare the reflexes of the preferred hand
and the less preferred.
 Another strength of our experiment was the identification of anomalies within the 25
trials performed per hand, through plotting a column chart. This enabled us to distinguish
which values were far off the general zone most bars strayed into. To eliminate these
anomalous results, we performed the trial a second time to receive an improved reading.
 A weakness of our investigation was the method with which we used to record the
response times of our dominant and non-dominant hands. Catching a ruler requires
measurements to be taken manually, which, especially since we are noting what position
the top of our fingers are grasping the ruler, may lead to parallax errors. The degree of
precision is also not particularly high, as with a ruler, one can only measure to 1 decimal
place accurately, and even that can be jeopardized by the fingers obscuring the ruler
markings.
To improve the quality of our results and its reliability from the reduce of human errors,
we should use a mouse, and a computer as both the visual stimulus and to record the
response times. With this setup of equipment, one must switch from the dominant hand
to the non-dominant to click the mouse button as soon as they perceive a particular image
or animation on the monitor screen. The computer will automatically record an accurate
value of the response time once the button is clicked. This will minimize any random or
human errors committed during our investigation.
 Another weakness of our experiment was the loud, classroom environment our
investigation was conducted in. The commotion and noise served only as a distraction,
one that possibly inhibited a faster reaction time, as concentration on the imminent
stimulus was not 100%. In future experiments, students should be spread out in multiple
laboratories so as to minimalize any distraction that can hinder the acquiring of as good
results as possible.