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Examples of well-written lab reports, by section:
Abstracts:
Reflexes require detection, relay, and response. The amount of time it takes for the response to
occur once the stimulus is given is known as the reaction time. [1] Our hypotheses were (1) reaction
time given a visual stimulus is slower than an auditory stimulus, and (2) prompted or predictable
auditory stimuli engender faster responses. A subject digitally responded to a simple visual or auditory
cue, and the average reaction time to stimuli (visual, auditory, auditory with prompt, and auditory with
predictable interval) were compared. [2] Visual reaction time was significantly slower than all types of
auditory cues (p<0.001). There was no difference in reaction time among auditory cues (p>0.05). Thus,
reaction times to visual stimuli are slower than reaction times to auditory stimuli, and that patterned or
prompted auditory stimuli have no effect on the speed of a reaction. Potential errors and future
experiments are discussed.
Different cue types have various effects on reaction times. In this experiment, forty-four
subjects used Labscribe and iWorx software to test their reaction times to four different cue types:
visual, auditory, prompted auditory, and predicted auditory. The results showed the longest average
reaction times for visual cues and shortest for auditory with prompt. Using t-test analysis, it was found
that there was a significant difference between the visual cue type and all other cue types, as well as
between auditory and prompted auditory. However, no significant difference was found between
auditory and predictable auditory or prompted and predictable auditory. A future study could be done
to explore the applications of this data in a real-life setting such as impacts on athlete performance.
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Introductions:
All humans respond to various stimuli, or changes in the environment, by reflexes. The stimulus
component of a reflex corresponds to the sensory neural circuits, while the response component
corresponds to the motor neural circuits.1 Once the neurons send sensory information of the stimulus to
the central nervous system, action potentials are then fired to produce a motor response such as a
muscle contraction.
Simple reflexes occur when single synapses are present between sensory axons and motor
neurons. All three nerve cell types involved, sensory, intermediate, and motor, are confined to the
spinal cord. As the brain is not necessary to perform these involuntary tasks, it only determines the
reflex has occurred after the action takes place. While complex reflexes involve additional interneurons
and motor neurons, they still don’t require brain function for the action to occur. The brain is not
directly engaged in low level associations that reflexes fall under, but only high level associations such as
problem solving.2 However, there exists a longer delay between the stimulus and response when a
complex reflex takes place compared to a simple reflex.
The reaction times for all reflexes vary depending on the cue type. The sensory process for
visual stimuli is more neurologically complex than auditory cues. While light must travel to the back of
the occipital lobe and back to the eyes, sound is only sent to the temporal lobe and back to the ear.3
Studies have shown that auditory cues may have a significant effect on the perceived intensity of a
visual cue.4 Other studies show that the effect of priming also impacts reaction times, as it activates
linkages to form as the subject prepares for the stimulus.5 The effect of predictable intervals can also be
investigated as a cue type that potentially alters reaction times.
The four cue types that were observed in this lab were visual, auditory, auditory with prompt,
and auditory with predictions. The effect of these cue types on the reaction times of the subjects was
investigated. Due to physiological background knowledge, it was believed that the auditory cues would
have faster reaction time over the visual cue. Also, from intuition, it was hypothesized that predictable
intervals would have the quickest reaction times compared to all the cue types.
An animal’s ability to survive is influenced by its ability to react to changes in its environment whether
that be voluntary or involuntary. One form of involuntary reaction is called a reflex. Much of what we do
everyday occurs due to our reflexes. A reflex originates when an external stimulus is detected by one or
more neurons. These neurons send information to the central nervous system, which processes the
information and decides how the body should react. The different types of reflexes can be broken down
into simple and complex. The complexity of the reflex pathway is dependent upon the number of
neurons that are involved. A more complex reflex typically results in a longer delay between the
stimulus and the response.[2] A simple reflex is produced through a single synapse between sensory
axons and motor neurons that are confined to the spinal cord. The general flow of information for a
human is as follows: stimulus, sensory neuron, spinal cord, motor neuron, and then response. [1] Two
examples of reflexes are visual and auditory reflexes. The acoustic reflex is the involuntary muscle
contraction of the stapedius muscle that occurs in the middle ear of mammals in response to sound
stimuli. The visual reflex, also known as vestibule-ocular reflex, occurs when the eye position
compensates for movement of the head. These reflexes can then induce a response. The time interval
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between the external stimulus and the response given by a subject is called the reaction time. [1] Many
factors affect reaction time such as age [3], distraction [4], and handedness [5].
This experiment looked at the visual and auditory stimuli’s roles in reaction time. The purpose of the lab
was to determine if people respond quicker to visual or auditory cues, in addition to auditory or
prompted auditory, and auditory or patterned auditory. One hypothesis was that the average reaction
time for an auditory stimulus would be shorter than the average reaction time for a visual stimulus. An
auditory stimulus only takes 8-10 msec to reach the brain [6], but a visual stimulus takes 20-40 msec. [3]
Our hypothesis was based off the assumption that the time it takes the stimulus to reach the brain
directly correlates with the time it takes for the response to be initiated. The second hypothesis was that
the average reaction time for an auditory stimulus would be longer than the average reaction time for
an auditory stimulus whose event time was known. Prompted auditory and patterned auditory fell
under the category auditory whose event time was known. When someone could plan for a response, it
was assumed that his reaction time would be quicker.
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Methods:
This experiment utilized the iWorx unit connected to Labscribe software running the AuditoryVisualReflexes-LS2 file. The experiment was broken up into 4 sections: visual, auditory, auditory with
prompt, and auditory at predictable intervals. 12 subjects preformed each section with 10 trials per
section for each subject. For a given subject, his reaction times for the given 10 trials were averaged
together for each section. These average reaction times for each subject were then averaged together
as a group so that each section had a final average reaction time. Therefore, the sample size was 12. [2]
Visual
The subject was instructed to press the Enter key during an iWorx recording immediately after observing
an event marker. The event marker appeared when another student, out of sight of the subject, quietly
and sporadically pressed the event marker button. The cues were between 5 and 10 seconds apart.
After the tenth cue, the recording was halted.
Auditory
The computer screen was covered with an opaque piece of paper. The subject was instructed to press
the Enter key during the iWorx recording immediately after hearing the click of the event marker button
being sharply pressed by a student out of sight of the subject. The cues were between 5 and 10 seconds
apart. After the tenth cue, the recording was halted.
Auditory with Prompt
The procedure for Auditory was repeated with an additional step. Right before each auditory cue was
delivered, the student said, “Ready,” in order to prepare the subject to respond to the auditory cue
(sharp click).
Auditory at Predictable Interval
The procedure for Auditory with Prompt was repeated with an additional requirement. The student
pressed the event marker button on a five second interval.
Statistical Analysis
After each experiment, the Analysis button was clicked. Next, one cursor was dragged to the onset of
the visual cue signal while a second cursor was dragged over the mark made by the subject responding
to the visual cue. Once the two cursors were in place, the reaction time appeared in T2-T1, located in
the Function Table. The mean reaction times for visual, auditory, auditory with prompt, and auditory at
predictable intervals were compared using a T-Test with alpha 0.05.
First, the Labscribe software was set-up with the Auditory-VisualReflexes-LS2 file settings. After
configuring, the computer and event marker were connected to the iWorx unit. The subject faced the
computer screen and was ready to press the Enter key when the event marker signal appeared. Another
student held the event marker behind the subject, ready to press the button. The Record button was
pressed on the computer screen, and the subject pressed the Enter key each time he or she saw the
visual cue on the right side. The button was pressed ten times for each subject, and forty-four subjects
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were used. After the tenth time the button was pressed, the Stop button was pressed. The reaction
times were acquired using Labscribe, and then averaged to get one reaction time for each subject.
Next, the computer screen was covered with a sheet of black construction paper. The subject
remained facing the computer screen and was instructed to press the Enter key when he or she heard
the click of the event marker. Another student held the event marker behind the subject, ready to press
the button. The Record button was pressed on the computer screen, and the subject pressed the Enter
key each time he or she heard the auditory cue from behind. Again, the button was pressed ten times
for each subject, with forty-four subjects. The same steps used for visual cues were repeated to acquire
the reaction times from Labscribe and average each subject’s times.
The subsequent parts required repeating the procedure for the auditory cues, but with one
differing step for each. In the third part, the subject was told before delivering each auditory cue to get
ready to respond. In the final part, in addition to repeating the procedure for the auditory cues, there
was a predictable five-second interval between each auditory cue. The same steps were used as before
to acquire the reaction times from Labscribe and average each subject’s times. After combining the data
for all forty-four subjects, a bar graph was produced and t-tests were conducted between each of the
four varying cue types.6
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Results:
The results of this experiment are shown in figure 1, which displays the average reaction time
for each cue. The total sample size was 12 groups. From the graph, it is clear that the response time to
visual cue was the slowest while that for the three different audio response times were similar (figure
1). In addition, six t-tests were conducted to determine whether the data from the different cues were
significantly different from each other (Table 1). Differences in data with a p-value of less than a 0.05
significance level were deemed significant.
Response Times (milliseconds)
600
500
*
400
300
200
100
0
Visual
Audio
Audio w/ Prompt
Audio at predictable
interval
Type of Cues
Figure 1: Average Response Times for Various Cues. The asterisk indicates that
the differences in response times between the visual cue and the three audio
are significant (P < 0.05 and n=12. Error bars show mean ± SE)
Table 1: P values for the T-tests
Visual vs Audio
Visual vs Audio w/ Prompt
Visual vs Audio at predictable interval
Audio vs Audio w/ Prompt
Audio vs Audio at predictable interval
Audio w/ prompt vs Audio at predictable interval
3.05E-06
3.17E-08
9.28E-08
0.385
0.530
0.799
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The order from fastest to slowest average reaction time is as follows: auditory with prompt, auditory at
predictable interval, auditory, and visual (Table 1 and Figure 1).
Table 1. Average Reaction Time (ms) for Different Stimuli
Stimulus
Auditory
Auditory with
Prompt
Visual
Average
Reaction Time
(ms)
Standard
Deviation
Standard Error
Reaction Time (ms)
600
500
Auditory at
Predictable
Interval
480.2
297.8
266.8
275.1
42.0
12.1
92.7
26.8
78.5
22.7
81.0
23.4
*
400
300
200
100
0
Visual
Auditory
Auditory with Prompt
Auditory at
Predictable Interval
Stimulus
Figure 1: Average Response Times for Various Cues. The
asterisk indicates that the differences in response times
between the visual cue and the three audio are significant (P <
0.05 and n=12. Error bars show mean ± SE)
The T-Test showed statistical significance when visual was compared individually to auditory (p=3.05E6), auditory with prompt (p=3.18E-8), and auditory at predictable interval (p=9.28E-8) (Table 2). The TTest did not show statistical significance when the different auditory scenarios were compared against
each other since all had a p>0.05 (Table 2).
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Table 2. T-Test: Comparing the Average Reaction Times of Various Stimuli
T-Test (p-value)
Visual
Visual
Auditory
3.05E-6*
Auditory with Prompt
3.18E-8*
Auditory with Predictable
Interval
9.28E-8*
* indicates statistical significance
Auditory
0.385
Auditory with
Prompt
-
0.530
0.799
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Discussions:
Because the p values comparing reaction times to visual and auditory cues, whether it be
unprompted and unpredictable, prompted, or predictable, were all greater than the alpha level of .05,
we rejected our null hypothesis that the reaction times to visual and auditory cues are equal.
Furthermore, because the p values comparing reaction times between the variations to of auditory cues
were all less than the alpha level of .05, we failed to reject the null hypothesis that the reaction times to
auditory, prompted auditory, and predictable auditory cues are equal. Essentially this allowed for the
conclusion that reactions to auditory stimuli are faster than those to visual stimuli and that the rate of
reaction to auditory, prompted auditory, and predictable auditory stimuli are equal. This is because the
processing of vision is more complex than that of audio and requires that the information be
transmitted through more neurons and synapses. Existing knowledge also supports this conclusion as
the article, Multisensory Auditory–Visual Interactions during Early Sensory Processing in Humans: A
High-Density Electrical Mapping Study, in Elsevier states that an auditory cue takes less than half the
amount of time to reach the cortex than does a visual cue (Foxe, 2002). Even in neonates the reaction
time to auditory cues is less than that to visual cues (Creighton, 1977).
However, our data is far from perfect. One unexpected result is the data point of 49 milliseconds
as an average response time to prompted auditory cues. Since other data points in this category range
from 205 to 352 milliseconds, this data point is clearly an outlier. Furthermore, the five second intervals
for the predictable auditory cues were measured without a timekeeping device making the intervals
slightly variable. This could account for the response time to auditory cues being deemed as equal to
that to predictable auditory cues.
Moreover, in additional experiments, we can test the reaction times to other sensory cues such
as olfactory, gustatory, and tactile cues. This has already been done for gustatory cues and has been
shown to be quicker in eliciting a response than either auditory or visual cues at just 100 milliseconds
(Halpern, 1983).
The hypothesis that visual reactions are slower than audio reactions was strongly supported by
the result of this lab. The average response time for the visual cue was more than a hundred
milliseconds slower than that of the three audio cues. Analysis of the t-tests comparing reaction times to
the visual cue versus any of the audio cues showed that the calculated p-values were all lower than the
significance level of 0.05. Thus, it is safe to conclude that reactions to the visual cue were significantly
slower than reactions to any of the three types of audio cues. However, the hypothesis that there were
significant differences in reaction times between the audio cues was unsupported by the data. When
the response times for the audio cues were compared to each other, the p-values were all higher than
0.05, so the differences in the results between the separate audio cues were not significant. Thus, the
second hypothesis was unsupported.
Possible reasons for the conclusions include the fact that reaction time is determined by a large
number of factors. The experiment seemed to indicate that out of the factors tested, the strongest
determinant of reaction time is by far the type of cue received, whether it be audio or visual. The
findings are supported by an early study on teenagers, which provided an average response time of
about 190 milliseconds for visual cues and about 160 milliseconds for audio cues (Galton 1899). An
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explanation for the results is that the greater complexity of a visual signal trumps all other factors and
causes a slower brain processing time when compared to an audio signal.
On the other hand, the data suggests that in the case of audio signals, neither prompts nor
priming contributed to significantly altering the response time. An experiment published a few years ago
showed that for long term auditory memory, priming does lead to a decreased reaction time
(Schweinberger 1997). Other studies have demonstrated the positive effect of prompts on complicated
tasks such as reading. Yet overall, there has not been many experiments on the effects of prompts or
priming on reaction speed for just audio cues.
Potential sources of error in this experiment include the fact that subjects reacting to the
anticipated audio cues were unable to precisely determine five seconds. Also, the way that some audio
cues were prompted might have been confusing to subjects. For example, some subjects might have
been misinterpreted a prompt as an actual click of the event marker. In addition, since the sample size
was not very large, the prompting/priming could have affected reaction times but in an amount so small
that they appeared as insignificant on the t-test.
Further experiments that could be done include experiments determining precisely if prompted
or primed audio cues elicit faster responses. Such experiments would require the same setup but much
larger sample sizes to ensure accuracy. Moreover, an experiment has shown that there is a negative
correlation between the intensity of the signal and its reaction time (Kohfeld 1969). Kohfeld’s
experiment could be elaborated by observing whether an extremely intense visual signal can produce a
faster reaction time compared to a less intense audio signal. Lastly, experiments can be performed to
determine how the speed of other cues such as odor cues compares to that of audio and visual cues.