Investigating the Effect of Discomfort on Reaction Time

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Investigating the effect of discomfort on reaction time

Purpose and method

The purpose of this investigation was to investigate the effect of discomfort on reaction time in humans, measured by dropping a ruler into a subject’s hand. Discomfort was caused by a bowl of ice. Background information

Information is carried from the sensory receptors to the central nervous system and back the to effectors by means of nerves. When a number of different processes are involved (a situation informally known as multitasking, research has shown that the brain tends to split to deal the different parts to carry out the tasks. The topic of interest is how having two problems to solve affects the speed of the brain in carrying out these tasks, and this will be tested by testing reaction time, or mental chronometry.


The hypothesis is that when the subject is experiencing discomfort they will be likely to take longer to catch the ruler. This is because, according to my background information, the brain will have fewer resources to put at its disposal as its attention will be split and this will result in slower reactions. Variables

The independent variable is the presence or absence of the cause of discomfort; in this experiment, ice. Due to the polar nature of the variable no error is associated with it.

The dependent variable is the distance in millimetres of ruler that passes through the subject’s hand before it was caught. It has an error of ±0.5 mm.

Below is a list of controlled variables.

Variable| Method of control|
Amount of ice| Variation in the amount of ice would lead to different amounts of discomfort, so this was kept the same for each subject.| Age of the subject| Age would naturally affect reaction time as older people are known to be less agile, so all of the subjects were the same age, 17 years.| Dominant hand of subject| All subjects were right-hand dominant. | Amount of time hand kept under ice| Variation in the amount of ice would lead to different amounts of discomfort, so this was kept at 30 seconds for each subject.| Equipment used

* Ruler, used to measure the speed of reactions.
* Bowl of ice, used to cause discomfort for the second half of the experiment. * Eight willing human subjects.

Eight volunteers were experimented on. Reaction time was measured by dropping a ruler between the subject’s thumb and index finger and measuring on the scale of the distance on the ruler when it was caught; a larger distance would mean a slower reaction time. This was done six times with each subject; for three of those six the hand was placed in a bowl of ice prior to testing.

Annotated diagram of experimental procedure.

Data collection and processing

Subject| Discomfort absent (mm)| Discomfort present (mm)| 1| 213| 312| 92| 178| 160| 213|
2| 392| 140| 139| 302| 215| 242|
3| 273| 47| 134| 92| 70| 162|
4| 260| 413| 254| 156| 154| 250|
5| 89| 190| 126| 302| 194| 94|
6| 166| 255| 142| 292| 351| 189|
7| 245| 221| 299| 270| 497| 212|
8| 150| 80| 100| 180| 190| 260|

The error for each measurement was ±0.5mm.

First of all the means of these values will be calculated to provide two values for each subject (all values to 3 significant figures). The mean is calculated by the following formula:

Example calculation for the mean.

Example for the ‘discomfort absent’ values for the first subject. Values: 213, 312, 92.

= (213 + 312 + 92) ÷ 3 = 206

i.e. distance on the ruler divided by three.

Subject| Discomfort absent (mm)| Discomfort present (mm)| 1| 206| 184|
2| 224| 253|
3| 151| 108|
4| 309| 187|
5| 135| 197|
6| 188| 278|
7| 255| 326|
8| 110| 210|

These values will then be plotted into a simple bar chart.

A graph showing the differences in reaction times with discomfort present and absent for eight different...
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