EFFECTS OF PSYCHOLOGICAL STRESS ON REACTION TIME
The Effects of Psychological Stress on Reaction Time
Jade Vega
University of Maryland University College
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Abstract
Psychological stress impacts, and has the potential to impact, many aspects of individuals’ lives,
including physiological and emotional states. Research correlating anxiety, sleep deprivation,
and other factors which can be closely aligned with psychological stress, indicate that perhaps
psychological stress can lead to an increase in individual reaction time. This study recruited 100
adult participants who do not have any diagnosed mental disorders which could be the cause of
their stress. Half of the participants were assessed and placed in a “significantly psychologically
stressed” group, and half were considered non-significantly stressed. Participants then
completed a simple, computer-based reaction time task. Results of the trials, which are
inconclusive but suggest future research is warranted, are presented here.
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The Effects of Psychological Stress on Reaction Time
Introduction
Psychological stress affects each person differently, although its effects can include a
wide range of emotional and physical symptoms. Stress may be associated with daily routines,
or caused by sudden life changes and trauma. Individuals respond to and perceive their stress
levels uniquely. Research has shown that significant stress can also cause increases in heart rate,
blood pressure, and respiration rates (Costin, Rotariu & Păsărică, 2013). Stress can affect a
person’s thoughts and feelings, behavior, and physiological state.
Since stress can be
distracting, it may affect a person’s ability to react as quickly to stimuli as those who are not
experiencing significant stress.
Many known factors influence reaction time, including arousal or states of attention, age,
mental and physical fatigue. Several of the factors which affect reaction time can be effects of
psychological stress. Several studies have studied the effects of stress on reaction time, although
few have made the distinction of “mental” or “psychological” stress, and this factor is usually
studied along with others. One study, for example, studied the effects of psychological stress on
reaction time, along with studying the effects of gender and color of stimulus on reaction time.
The study found that psychological stress "resulted in a significant decline in the reaction time"
to a specific color in male participants (Venkates, Ramachandra, Baboo & Rajan, 2002, p. 560).
It is difficult to draw specific conclusions about the role of psychological stress from this study,
since a number of factors were being tested. It also only points to a decline in reaction time for
males.
A study published in "Language Learning" found that stress increases processing time for
language skills (Rai, Loschky, Harris, Peck, & Cook, 2011). The study does not deal with
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simple visual stimuli, but involved testing the effects of several factors on foreign language
readers' inferential processing during reading comprehension. Although the manner of testing is
very different, the study does show that stress decreases comprehension, as well as reaction,
time. Another study focused on the effect of premenstrual stress on audiovisual reaction times.
The study, however, like many others, was not measuring effects of solely psychological stressin this case, the factor of stress in premenstrual phases was found to result in decreased reaction
times (Das, Gandhi, & Mondal, 1997). One study that focused strictly on the effects of stress
and anxiety on reaction time relied predominantly upon experimentally induced stress (Farber &
Spence, 1956). The effects of experimentally induced stress were unclear, and thus nonconclusive.
Although there is a lack of study in regards to the particular effects of non-experimentally
induced psychological stress on reaction time, many researchers have published findings that
indicate stress may have a significant impact. Many researchers have noted the fact that
significant, or excessive, stress can cause: anxiety, reduced concentration, sleep difficulties, and
more (Swann, 2011). Jones and Hardy found that anxiety tends to result in an increased reaction
time (1988). Sleep deprivation, another symptom which may be associated with psychological
stress, has been found to play a role in increasing participant reaction time (Carlozzi, Horner,
Kose, Yamanaka, et al., 2010).
There have been enough findings about the effects of stress to lead researchers to believe
psychological stress may impact reaction time, and this subject warrants further study. The
hypothesis of this study is that stress increases reaction time.
Method
Participants
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There were 100 participants in this study. The participants were placed into two groups:
Group A was comprised of participants who were experiencing significant psychological stress
at the time of the study, and Group B included those who were not experiencing significant
psychological stress. Each group contained 50 participants, with half of the participants being
male and half being female in each group. Participants were recruited via an online system. A
small cash incentive was offered to participants to compensate for the time needed to perform
testing before the study. A disclaimer was added that any individuals who have received a DSM
diagnosis of a psychological disorder did not qualify for this study. Researchers in this study
were only interested in the effects of psychological stress that cannot be attributed to a
psychological disorder.
Materials
Two self-report paper examinations, the PSM- 9 measure of psychological stress and a
Perceived Stress Scale were given to participants after initial interviews. A blood pressure cuff,
sphygmomanometer, and stethoscope were used to measure participants’ blood pressure. A
cardiovascular belt was used to measure heart and respiratory rates. The reaction time study was
computer-based; only a computer was needed for the study itself.
Design
There were two conditions in this study: significantly psychologically stressed and not
significantly psychologically stressed. Participants were evaluated by a psychiatrist in a short
diagnostic interview, administered self-assessments of their stress levels, and given physiological
tests (heart rate, respiratory rate, blood pressure) before being placed into the appropriate group.
Participants’ reaction times to a simple computer-based task were then measured and statistically
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analyzed to determine whether or not there is a significant difference in reaction time between
groups.
Procedure
Upon realizing that there was a lack of data in the scientific community regarding the
relationship between stress and reaction times, the research team discussed experimental ideas
and completed a Review Board Form (RBF), also referred to as an IRB form. A copy of this
form can be found in the Appendix.
After participants volunteered to participate in the study, they were given an appointment
time to undergo further diagnostic testing, in order to place them in the correct groups. In order
to rule out any participants with symptoms that may meet the criteria for a DSM-V diagnosis of a
psychological disorder, a brief diagnostic MINI interview was given to all participants. MINI
stands for “mini-international neuropsychiatric interview". The interview lasted for
approximately fifteen minutes.
Following the interview, all remaining participants were given self-assessments. The
first self-assessment was a psychological stress measure, or PSM. The PSM-9 is a 49-item selfreport measure of psychological stress (Lemyre & Lalande-Markon, 2009). Participants
answered questions relating to their personal perceptions of stress in their lives for the four or
five days prior to assessment. A perceived stress scale, consisting of ten questions related to the
participants’ perceptions of events in the past month, was then administered. The Perceived
Stress Scale, PSS, assesses "the extent to which respondents find their lives unpredictable,
uncontrollable, and overloaded" (Al kalaldeh & Shosha, 2012, p. 45). These aspects are
important in order to understand individuals' stress experience, including the severity. PSS has
been shown to be an effective way to measure the relationship between individuals' perception of
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stress and their risk for diseases and behavioral disorders (Al kalaldeh & Shosha, 2012).
Understanding participants' perceptions of their stress levels was crucial in order to place them
into the appropriate groups.
After the self-report measures were administered, physiological data were taken. Since
significant stress may impact a person’s resting heart rate, respiratory rate, and/or blood pressure,
all of these were measured. In order for a participant to be placed into the psychologically
stressed group, they needed to have one abnormal rate which may be indicative of a stressinduced reaction. For example, acute stress has been known to increase systolic blood pressure.
If a participant had an increased systolic rate, combined with scores evaluated by a professional
as indicating high levels of stress, they were placed into the significantly psychologically
stressed group. Overall, participants were placed into the psychologically stressed group if they:
were not experiencing stress as a byproduct or symptom of a psychological disorder, indicated
on self-report measures that they feel overwhelmed with stress, and had some sort of abnormal
physiological rate (heart, respiratory, or blood pressure).
Participants had a short break after the physiological tests, and proceeded on to the
computer-based simple reaction time task. In the task, participants were shown a visual stimulus
and needed to react to the stimulus as quickly as possible. In each trial, the screen was white for
short times, which varied with each trial, and then a color would appear on the screen. As soon
the color appeared, the participants were to press any key. This trial was repeated 20 times and
information about their reaction times was gathered and statistically analyzed.
During the statistical analysis of data collected, means for the reaction times of each
group were calculated. Standard deviations and standard errors of the mean for the samples were
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also calculated. A two-sample unpaired t test was performed to calculate the t and p values for
the data. An alpha level of .05 was employed to determine the significance of the difference.
Results
This study was aimed at discovering what, if any, relationship exists between
psychological stress and reaction time. Researchers believed that significant psychological stress
would distract individuals, and produce emotional and physiological symptoms that would result
in their reaction times being lower than non-stressed persons.
Data was collected from all 100 participants’ trials and statistically analyzed. The mean
reaction time for the psychologically stressed group was .476 seconds. The mean reaction time
for the non-psychologically stressed group was .347 seconds.
The results are shown in the
figure below. The standard deviation of the psychologically stressed group’s reaction times was
.406. The standard error of the mean of was .057. The standard deviation of the non-stressed
group’s reaction times was .224. The standard error of the mean was .032.
T test calculations were performed with 98 degrees of freedom. The t value for this data
was 0.0516. The two-tailed p value of this data was calculated to be 0.0516. This is not quite
statistically significant. However, it is important to note that this is close to statistical
significance; future studies may yield results that indicate a stronger statistical relationship.
Figure 1.1 Mean of psychologically stressed and non-psychologically stressed reaction times
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MEAN REACTION TIMES OF STRESSED AND
NON-STRESSED GROUPS
0.5
reaction time in seconds
0.45
0.4
0.35
0.3
0.25
0.476
0.2
0.347
0.15
0.1
0.05
0
STRESSED
NON-STRESSED
Discussion
This study attempted to discover whether or not non-experimentally induced
psychological stress has an impact on reaction time. While there was a difference, it is not
conventionally considered to be quite statistically significant. This study is one of the only that
has focused solely on psychological stress and reaction time. Its findings provide support for the
hypothesis that stress impacts reaction time, although future research and more conclusive results
regarding this type of stress are needed.
A theoretical implication of this study is that persons who are psychologically stressed
may take longer to react. Although the results are not highly significant and are preliminary,
future research could shed light upon further implications. Being able to quickly respond to
situations, especially dangerous ones, in everyday life is vitally important. Individuals who
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experience significant psychological stress may be at a disadvantage when participating in sports
and daily activities, such as driving.
Measures of psychological stress, such as the diagnostic interview and self-assessments
utilized in this study, are inherently subjective. The study is limited by the fact that these
determinations about levels of stress are subjective. Different measures, such as tests which
included varied types of stimuli (ie. Reacting to different colors, etc.) may have yielded more
reliable results. Another limitation of the study is that the reaction time tasks were short, and
beyond the first set of 20 trials, were not repeated. Repeated tasks, and thus more data collected,
may have yielded more conclusive results.
Future research could incorporate more reaction time tests, larger sample size and
perhaps more varied methods of testing them. More rigorous assessment methods, such as
longer diagnostic interviews, may also be a component of future studies. Self-assessments that
reveal more information about participants’ history with stress and any accompanying symptoms
may also be useful in placing participants into groups to reduce possible error or individual bias.
Everyday life tends to be more work and stress than time for individuals to rest. As a
result, many people suffer from significant levels of stress. Stress has been linked to many shortterm and long-term physical and emotional complications. Understanding the effects of stress
can lead researchers and individuals to better understand how stress works, and thus how to
better prevent its deleterious effects.
Appendix
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Review Board Form
Title of Experiment: The Effects of Psychological Stress on Reaction Time
Name(s) of Researchers: Jade Vega
1. Briefly describe the purpose of the experiment.
The purpose of the experiment will be to examine the relationship between significant
psychological stress and reaction time.
2. Who will be the participants? How will they be chosen?
The participants will be adults who do not have any psychological disorders, and who do not
qualify for a DSM-V diagnosis. Recruitment and sign-ups for the study will be online, and
participants will be screened by a psychiatrist before other assessments to ensure that it is not
likely their stress is attributable to a psychological disorder.
3. How will confidentiality be maintained? How will you identify data associated with each
participant?
Confidentiality will be maintained by using study codes for all documents containing
information about participants, which only primary researchers will have access to. No dates of
birth or other identifying information, beyond basic information, will be collected and after the
study this identifying basic information will be destroyed.
4. Are there any potential risks, physical or psychological, to participants? If so, what? How
will you, as the researcher, minimize these risks?
There will be no physical risks posed to participants. The tests that will be administered to
determine participants’ stress levels may create more stress for some individuals. To minimize
this additional stress, self-assessments will be kept brief and physiological tests will be basicheart rate, blood pressure, and respiratory rate. Heart rate and respiratory rate will be measured
simultaneously.
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5. Describe your debriefing procedures.
Participants will be asked whether, at any point during the initial phases or study itself, they felt
suspicious or unclear about the procedure. We will also assess participants' states of mind before
they leave; we will ask if they have any further questions, how they are feeling (if they are
feeling at least the same as when they arrived- if not, referred for counseling), and asked if they
have any ways to improve similar studies in the future. We will also request participants not to
reveal information about the study to others, thank them for their participation, and provide them
with the head researcher's contact information in case any future questions or concerns arise.
6. Describe the procedures of the study. Give enough detail so that the Board can make a
judgment about your study.
Once suitable participants (adults without a DSM diagnosis) are recruited, they will be
administered brief physiological (heart rate, respiratory rate, and blood pressure) and
psychological (self-report information about stress in their lives, brief interview with a
psychiatrist to rule out any persons whose stress may be attributed to a mental disorder)
assessments. This information will be used to place participants into two groups: participants
that are significantly psychologically stressed at the time of the study, and participants who are
not significantly psychologically stressed. Participants will complete a short, computer-based
test which asks them to respond to a visual stimulus by pressing any key. Reaction times will be
recorded by the computer and statistically analyzed.
Jade Vega
11/22/13
_______________________________
Researchers Signatures (may be electronic)
___________
Date
References
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Al kalaldeh, M., & Shosha, G. (2012). Application of the perceived stress scale in health care
studies. an analysis of literature. International Journal of Academic Research, 4(4), 4550.
Carlozzi, N., Horner, M., Kose, S., Yamanaka, K., Mishory, A., Qiwen , M., & Nahas, Z. (2010).
Personality and reaction time after sleep deprivation.Current Psychology, 29(1).
Costin, H., Rotariu, C., & Păsărică, A. (2013). Identification of psychological stress by analyzing
electrocardiographic signal. Environmental Engineering & Management Journal , 12(6),
1255-1263.
Das, S., Gandhi, A., & Mondal, S. (1997). Effect of premenstrual stress on audiovisual reaction
time and audiogram. Indian Journal of Physiology and Pharmacology, 41(1).
Farber, I., & Spence, K. (1956). Effects of anxiety, stress, and task variables on reaction
time. Journal of Personality, 25(1).
Lemyre , L., & Lalande-Markon, M. (2009). Psychological stress measure (psm-9): integration
of an evidence-based approach to assessment, monitoring, and evaluation of stress in
physical therapy practice. Physiotherapy Theory & Practice, 25(5-6), 453-62.
Rai, M., Loschky, L., Harris, R., Peck, N., & Cook, L. (2011). Effects of stress and working
memory capacity on foreign language readers' inferential processing during
comprehension. Language Learning, 187-218.
Swann, J. (2011). Understanding the common triggers and effects of stress. British Journal of
Healthcare Assistants, 5(10).
Venkatesh, D., Ramachandra, D., Baboo, N., & Rajan, B. (2002). Impact of psychological stress,
gender and colour on visual response latency. Indian Journal of Physiology and
Pharmacology, 46(3).