Fighter Pilot A Statistical Analysis of Reaction time and its Correlation with Dominant & Non-Dominant Hands

Elizabeth McKnight

Fighter Pilot

A Statistical Analysis of Reaction time and its Correlation with Dominant & Non-Dominant Hands

Introduction

This experiment seeks to determine reaction times in two groups of matched subjects; dominant and non-dominant hands, using the ruler drop test.

Reaction time experiments are performed to measure the alertness of the mind and will give an indication of the speed of the reflexes that different groups of varied individuals have. The experiment tests how long it takes the brain to translate visual information into the voluntary motor commands, actions which lead to a ruler being grabbed. The shorter the length at which the ruler is grabbed, the shorter time and therefore the faster the person’s reaction. The controls of these processes within the human body are the responsibility of the nervous system which is the seat of voluntary and involuntary movements along with language, emotion and memory. (1)

The experiment begins with an environmental stimulus via light reflected from a moving ruler being dropped from a height above the subject’s hand. (1) This transmits into a sensory nervous impulse within the optic nerve. Beginning in the retina of the eye, information is detected by photoreceptors (rods and cones) they relay the visual signals on to bipolar cells which transmit on to ganglion cells. (2) The axons of all ganglion cells in the retina of each eye join to form the optic nerve. The information (an electrical transmission) is then passed through to the mid brain and the thalamus. (1) The information going to the midbrain does not reach conscious levels but rather produces pupillary reflexes (which are controlled by the autonomic nervous system) and eye movements. (1) In the thalamus, ganglion cell axons transmit signals to the primary visual cortex in the occipital lobe of the cerebrum, this visual association region recognizes the meaning of the visual impulses and the cortical cells then send messages to other "higher" cortical areas, associative centres of the brain, where the information is questioned and transformed into a response. (2) The transmission is then sent to the precentral gyrus, the primary motor complex and a transmission of a motor impulse is carried down to the spinal cord to motor neurons and finally to the muscles of the hand effecting the movement through the contraction of muscles. (2)

This journey of information from receptor to effector in the human body is very complex due to the various neurons and synapses involved. Due to this complexity the human brain and nervous systems ability to process information and relay a response may be hindered or facilitated by many different internal or external factors.

Fatigue influences human performance and affects individuals to varying degrees, ranging from slight to catastrophic. (3) Increasingly, fatigue has been claimed as the primary cause of many major accidents, for example, the incidents of Exxon Valdez oil spill (7) (1989) list fatigue as a root cause, along with many vehicle and work place accidents worldwide. (4) Studies have shown that fatigue causes the reverse of the learning process; moving the decision making from skill based cognition to knowledge based causing people to rely more on their working memory rather than on their long term memory for task completion, and in turn people work harder with lower performance. (5) (6) In extreme cases fatigue may cause a person to disengage briefly in a so-called 'micro-sleep', if this happens at a critical time, accidents may result. (4) A similar factor to fatigue is alcohol, a substance which society believes to be the biggest factor influencing accidents. A recent reaction time study in Stanford University (8) has shown that subjects deprived of sleep had longer average reaction times than that of the intoxicated subjects, this research sheds worrying light upon many occupations in society today that allow employees to work between 12 hours to 24 hours a day, for example, doctors or pilots. Increasing the quantity of alcohol consumed causes the reaction time to become highly impaired (9) (varies between individuals), this is due to the sedative and hypnotic effects as it depresses the central nervous system. (10) It directly interferes with the binding of certain neurotransmitters, especially acetylcholine. (11) However, it is most likely acetaldehyde/ethanal (a primary metabolite of ethanol) which causes differences in brain function. (10) Acetaldehyde is known to react with dopamine (yielding salsolinol) and also to react with tryptamine (producing tetrahydroharman), both by-products have psychotropic activity. (12)

Disability or illnesses, such as schizophrenia have shown to affect performance due to the cognitive defects in the brain caused by a dysfunction of the dopamine system. Studies show that patients with persistent illness perform poorly when given a reaction time task. (13) Lesser illnesses such as the influenza may also cause poor performance; this is due to the intense feeling of fatigue and nausea inflected upon the sufferer. (14) Distractions or lack of concentration and old age are other major factors involved in slowing the reaction time of subjects.

The most widely used psycho-stimulant substance in the world is caffeine which can be used to promote the nervous system and its responses. It works via modulating neurotransmission in the nerve cells by attaching to adenosine receptors, adenosine in the brain binds to receptors which causes drowsiness and eventually sleep by slowing down nerve cell activity. (15) The false attachment of caffeine prevents adenosine from binding and doing its job thus increasing nerve activity and promoting the neurons firing in the brain. (18) The pituitary gland notices this activity and reacts by releasing hormones that tell the adrenal glands to produce adrenaline (epinephrine). The adrenaline then gives the body a boost by activating the sympathetic division of the autonomic nervous system. (15) Further research into the effects of caffeine shows its levels of addiction and impacts, as caffeine works similarly to drugs like cocaine (though on a much smaller level) it blocks adenosine reception so making a person feel alert, (15) injects adrenaline into the system and gives a person a boost while manipulating dopamine production to make a person feel good. Long term this can mean many things to a person’s brain and their reaction time. For instance, a cup of coffee can take between 3 to 12 hours for the body to eliminate one half of a caffeine dose; this is called the half-life of caffeine. Drinking caffeine in the morning and again in the evening will lead to it staying in the blood every hour of the day. The effect of caffeine in the body will be active 24/7. Several factors can shorten or lengthen the half life of caffeine, such as smoking, medications and diseases. (15) People addicted may drink ten or more caffeinated beverages a day, especially if under stress or work early/long hours. A study (16) on the effects of caffeine withdrawal on reaction time and its impact on general well being proved to affect alertness, hand steadiness and reaction time, particularly plummeting on day two of the study and slowly restoring itself by days six and seven. The subject’s performance at the end of the trial, after a full withdrawal, was as good as it was before which shows the caffeine only had an effect insomuch as the subject’s body was craving it. (16)

Nicotine works in a slightly similar way as caffeine, it binds to receptors that normally bind to the neurotransmitter acetylcholine. (17) Acetylcholine is involved in delivering signals from your brain to your muscles; it also controls energy levels, breathing, cardiac rhythm and oversees the flow of information in your brain playing a vital role in learning and memory. (17)The binding of nicotine in place of acetylcholine causes cholinergic neurons to release more acetylcholine from the brain and thus heightening the neuron pathways. Through these pathways nicotine improves reaction time and the ability to pay attention, making people feel like they ...

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A more natural boost for reaction times is achieved through a physically active lifestyle. Exercise promotes and stimulates the nervous system by improving mood through the release of endorphins (21, 22) and cognition via neurogenesis. (19) Research has shown that at a cellular level the mild stress generated by exercise stimulates an influx of calcium which activates transcription factors in existing hippocampus neurons. The transcription factors initiate the expression of the brain-derived neurotrophic factor gene (BDNF), which is involved with the formation of new neurons. (20) Also practice specifically affects the associative centres in the brain, so that a person can respond faster to what’s happening and allowing the flow of information along the visual and motor nerve pathways. (23)

The hemispheres of the cerebrum are specialized for different tasks, the left hemisphere is regarded as the verbal and logical brain, and the right hemisphere is thought to govern creativity, spatial relations, face recognition and emotions. (24) Also, the right hemisphere controls the left hand, and the left hemisphere controls the right hand. There is a possibility the left hand may be faster at reaction times involving spatial relationships. (24)

Due to these conflicting factors parameters must be set so to make this experiment a fair test. Firstly the independent variables (only changing factor) in the experiment and will be the dominant hands of one group and non-dominant hands of the other group.

The dependant variable (the factor influenced) in the experiment is a measure of seconds calculated by the measurement of distance dropped (centimetres on the ruler).

The controlled variables are all other aspects of the experiment which need to be kept the same to ensure that the method used will produce fair and accurate results.

These controlled variables include:

Keep all the subjects the same gender, Female
Keeping all the subjects within the same age group, 16 – 25
Allowing subjects a pre-run of all the reaction time game to encourage a confident performance
Subjects suffering from a cold or any other illness must not be tested
Making sure that tests are overseen by the author of the investigation so to prevent cheating
Subjects must have consumed lunch or at least eaten that day prior to test
Subjects must not consume caffeine prior to test
Non-smoking subjects to be tested only (may be hard to control as people lie)
Subjects that need or wear glasses not to be tested (20:20 vision only)
Subjects of a physically active nature to be tested only
Subject must all sit in the same particular position as depicted in the instruction sheet, Appendix 3
Ruler must be positioned in exactly the same position every time, bottom of ruler held within the area between the out-stretched thumb and first finger getting as close to the skin as possible but without touching
Participants arm should not move until the ruler begins to drop
Same ruler to be used for the entire experiment
Measurement to be read from above the thumb
Test must be held in a place of calm away from distractions
Each subject must do the ruler drop test three times and each time recorded
A subject that has taken part in the test must not take part again
Miss drops will be allowed to re-try but only once, further miss drops will be recorded as 100cm
A total of 30 subjects for each group to be tested

Preliminary work

The preliminary work carried out before the initial investigation allowed for a hypothesis to be made and gave an idea of possible changes within the variables before performing the actual test.

A group of ten women of a young age were used, although finding subjects that would pass the above criteria proved to be somewhat more difficult than expected and a leniency on the controlled variables may have to be allowed. The results of the preliminary work are below.

Table 1 Data from preliminary work; ruler drop distances of ten subjects shown in centimetres

Table 2 Data from preliminary field work; reaction time of ten subjects shown in seconds

The results from this test show that the overall reaction time was faster in the subjects with the dominant hands, thus allowing for a hypothesis to be drawn up.

After the results are recorded the dropping distances will be calculated into reaction times. This is achieved by following this formula:

t = time (in seconds); y = distance (in cm); g = 980 cm/sec (acceleration due to gravity). (23)

Inferential statistics will be implemented and mathematical techniques carried out using the sample means. A t-Test will be carried out to determine statistically if there is a significant difference between the means or whether they occurred by chance. A calculation of 95% confidence limits/intervals (CIs) will also be carried out as a 95% CI of the mean indicates how confident we can be that the true population mean lies within the calculated confidence interval, it communicates more useful information than probability values in hypothesis testing. Descriptive statistics will be used via graphical representation of the data to allow for further analysis.

Hypothesis

Null hypothesis: H0 - There will be no significant difference in the reaction times between the dominant handed subjects and non-dominant handed subjects

Alternative hypothesis; H1- Non-Dominant handed subjects will have a significantly higher reaction time than the dominant handed subjects

Method

Apparatus

A meter long ruler
Questionnaire – Appendix 1
Record sheet – used to record results – Appendix 2
Private area, as concentration is required on behalf of the participants a quiet room/area to be used
Chair and table, to allow subject to sit on and table for subjects arm and hand to lie flat
Pen, to note the times recorded
Instruction sheet, to be read out to each subject, Appendix 3

Participants

The total sample size is sixty participants taken systematically from students in Belfast Metropolitan College, College Square East, Belfast city centre. (n=60). Each subject must first be screened to see if they are correct for the test.

Procedure

Arrange with students union staff in Belfast Metropolitan College, College Square East, that an area will be free for use at a certain time during the day. 11am to approximately 1.30pm
Arrange for a quiet area to be reserved
Set up area with table, chair, ruler, instruction sheet, pen and record pages
Beginning with dominant hands start approaching random women and asking if they wish to participate
If answered Yes begin asking questions from questionnaire, if answer No return to point four
Participants must answer questions successfully according to the requirements of the controlled variables to take part in the test, answers recorded.
Upon finding a suitable subject bring them over to the prepared quiet area
Read to or allow participant to read instruction list
Make sure participant is sitting correctly, knees together, arm along the side of the table with hand positioned properly, thumb stretched out, use Appendix 4 as a reference
Hold ruler so that the very bottom of it is in line with the table top and is sitting very close to subjects finger and thumb
Remind participant to concentrate
Wait an appropriate amount of time, ranging between 5 and 10 seconds to try and catch the subject by surprise
Begin experiment by dropping ruler
Subject should catch the ruler
A measure of the dropping distance in centimetres should be recorded from just above the thumb
Repeat test two more times with this subject
Repeat point four to sixteen until 30 participants have done the test
Now repeat point four to seventeen but change to non-dominant hands, continue until 30 participants have done the test or within the time limit

Risk assessment

Safety is an important aspect in every experiment, even if the experiment seems to be very harmless. Things to take into consideration are:

Ensure each participant is fully aware of the experiment
Experiment is kept out of the way of people as they walk by, bags and coats kept in a safe place
When dropping the ruler make sure to drop it straight down and not at an angle as it may hit the subject on the knee or foot

Results

Table 3 Dropping distances of two paired samples; Subjects: Dominant hands & Non-Dominant hands

Table 4 Dropping distance of dominant hand sample & conversion into Reaction Time in seconds

Table 5 Dropping distance of non-dominant hand sample & conversion into Reaction Time in seconds

Table 6 Data showing mean reaction time for every subject within both samples

Table 7 Data showing overall mean Reaction Time for each sample

95% Confidence Limits Calculation

Standard Deviation Formula Standard Error of the Mean Formula

Confidence Limits Formula

Upper Confidence Limits = X + (t x standard error of the mean) (24)

Lower Confidence Limits = X - (t x standard error of the mean)

t value is taken from critical value tables at a 0.05 probability and N – 1 degrees of freedom

Table 8 Calculated data from both samples

t-Test

H0 – There is no significant difference between dominant hand reaction times and non-dominant hand reaction times. µnon-dominant = µdominant.

H1 – Non-dominant hands will produce a significantly higher reaction time than the dominant hands. µnon-dominant > µdominant.

Level of significance is set at 5%, allowing for a 95% confidence that the result is not due to chance
The computer is used to calculate the probability that the results happened by chance. At a one-tailed test (as ‘higher than’ has been specified in the alternative hypothesis) and type one test because the sample is paired and are of equal variance. t = 0.251
Reject H0 if t > 1.676 (To reject the null hypothesis the calculated value must be higher than the critical value of a one-tailed test with 5% confidence level and at 58 degrees of freedom) the calculation was carried out on the computer which calculates the probability, therefore reject H0 if p < 0.05.
Since the calculated value of p is 0.251 and higher than 0.05 the null hypothesis must be accepted and the alternative hypothesis rejected.
There is a no significant difference between the reaction times of dominant and non-dominant hands

Discussion

The initial results visible from table seven shows that the dominant handed subjects are the faster group. This is confirmed further with graph one where it is quite obvious that the non-dominant handed subjects were slower. At closer analysis of the results there is only a small margin of difference between the two, a three percent difference. This is a very small variance and the first piece of evidence to prove that the difference in means may have occurred by chance.

The calculated 95% confidence limits, as plotted on graph one show clearly that there is a major overlap, the values of the limits are practically matched with nearly perfect symmetry, also the values for the confidence limits seem rather wide, indicating that the data is not very reliable. It seems very justified at this point to accept that there is no significance between the difference in the two sample means and that it occurred by chance.

The t-Test, statistically tests the significance of the different means by calculating a probability where the null hypothesis is rejected if the P value is smaller than 0.05. In this experiment the calculated value for P was higher than 0.05 and so the null hypothesis must be accepted. This statistical calculation supports that of the 95% confidence limits with evidence that the means of the two groups of data were not significantly different from each other. This concludes that the experimental hypothesis must be rejected and the null hypothesis accepted.

From this analysis it is true to say that the individual data from the two groups may be extremely accurate, but the samples may be too small to be sure that each is a reliable estimate of the population. Moreover, there may be other reasons why the reaction times did not differ, for example accurately following the controlled variables stated in the introduction became very difficult to enforce as the time set out for the experiment was running out. Willing and accepted participants became harder to find so leniency was allowed upon those who smoke and consumed caffeine.

Reviewing the research pointed out in the introduction, questions may be raised. How many cups of coffee/tea did the subjects in this experiment consume? Did they have a lot of caffeine the night/day before? Have any of the subjects decided to stop drinking caffeine recently causing an adverse affect upon them? If this investigation were it to be repeated these variables may need to be considered.

The next point observed while doing the experiment which may have caused some short comings was the area chosen for the experiment, the student’s union, a rather noisy area with many people coming and going. Although great effort was put into reserving a quite table in corner, however the lunch hour rapidly approached and the student’s union became full of students talking, eating and playing pool. This may have caused a great deal of distractions for the participants and they gave the experiment less than of their full attention.

Also some subjects that took part were in the middle of lunch which may have had an effect as different foods give varying amounts of energy. Subjects also appeared disinterested; this may be because they wanted to continue their lunch so they were not giving 100% effort. Some subjects also seemed rather confused, although the experiment was explained and even shown to them, signs of confusion and laxidasical approach could be seen.

Further investigation into the factors that may influence reaction times is 'arousal' or state of attention, including muscular tension. Reaction time is fastest with an intermediate level of tension and deteriorates when the subject is either too relaxed or too tense. Research has found that exercise and tension before and during reaction time tests gives an overall faster time, although it seems to improve cognitive reactions more so than muscular reactions. (28)

Due to these findings stated within the discussion new parameters should be set when investigating this experiment further. Begin by arranging with a larger group (100+) of willing and eager participants. The group must be at an age group around 20 and extending no more than two years in any direction, same gender and all non-smokers. The group must also agree to not drink caffeine for at least a week before the experiment (a prize or object of value may be needed to convince subjects to agree to take part in the experiment, or incorporate the experiments to a clinical trial where subjects are being deprived of caffeine). Certain measures will also have to be taken to determine whether participants are telling the true about the criteria.

Just before the reaction time experiment takes place each participant will do a short warm up exercise with stretching, especially the arm to be used in the test. Then in between each ruler drop the participant should clench and tense arm and fist for five seconds. This arousal of the muscles should promote a heightened response.

A quite empty room should be reserved to prevent any distractions and the experiment to be held over the course of a number of days allowing for a greater number of participants to take place. Also a range of different reaction time games should also be used to test the dominant and non dominant hands, games such as interactive games on the internet which involve clicking the mouse when a stimulus appears on screen, here are some examples: , , .

Conclusion

This investigation was set out to determine where there was a significant difference between reaction times of dominant handed subjects and non-dominant handed subjects of a total of 60 participants. The experiment was held over an afternoon and the results were recorded. Given the time constraints a number of the controlled variables were not followed accurately giving rise to possibly invalid results. From the initial results dominant hands proved to be the fastest:

Dominant hand sample mean = 0.265 seconds
Non-dominant hand sample mean = 0.272 seconds

Using these results a number of calculations were carried out to test whether these means are a product of chance or whether dominant hands have a faster reaction time

The 95% confidence limits for each sample were calculated and were found to be practically matching and gave an entire overlap between the two groups when plotted in a bar chart. The widths of the intervals were also rather large further providing evidence of the unreliability of the data; this is highly visible in the graph drawn. A statistical t-Test was calculated for further evidence of a significant difference and the calculation gave a probability value of p = 0.251 which is higher than that of 0.05, set at 5% significance, resulting in the alternative hypothesis being rejected.

The evidence found in this experiment provided the necessary information which allowed for the experimental hypothesis to be rejected and the null hypothesis accepted:

Dominant hands and non-dominant hands have no difference when tested in reaction times.

Further investigation may be needed to fully confirm that this is true of the entire population, to include a larger sample and stricter controlled variables.

Word count 5,232

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Teacher Reviews

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Adam Roberts

25th of Oct 2014

An extremely detailed and well though through account of the investigation. Background theory described using A level standard language and a clear awareness shown of the various factors which may affect reaction times. Results presented clearly and statistical analyses performed correctly. 5 Stars

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