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Investigating human reaction times

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Explainer Video

Tutor: Jasmine

Summary

Investigating human reaction times

In a nutshell

Reaction time is the time taken to respond to a stimulus, it is affected by factors such as age, gender or drug use. By measuring how quickly a person catches a ruler you can investigate the effect of a known factor on human reaction time.

Equipment list

The following equipment can be used to evaluate the effect of a factor on reaction time.

Equipment	Use
$30\space cm$ ruler	To be dropped and caught again.
Table	For the person who's reaction time is being tested to place their non-dominant hand.
Chair	For the person who's reaction time is being tested to sit on.
Caffeinated drink	To drink.
Radio	To create background noise.

Experiment 1: Investigating the effect of caffeine on reaction time

Experimental variables

Every experiment will have an independent, dependent and control variable. The independent variable is the variable that you change. The dependent variable is the variable which depends on the independent variable, therefore it is the one you measure. The control variable is the variable that is kept the same during the experiments.

Independent variable	$Drinking \space a \space caffeinated \space drink.$
Dependent variable	$The \space distance \space caught \space on \space the \space ruler.$
Control variables	$Persons \space dominant \space hand \space should \space always \space be \space used, \newline height \space ruler \space dropped \space should \space always \space be \space the \space same, \newline no \space caffeine\space should\space be\space consumed\space before\space the\space experiment,\newline the\space ruler\space must\space be\space dropped \space in\space the\space same\space direction.$

Safety precautions

When carrying out experiments it is very important you consider safety precautions. However, in this experiment there are no significant hazards to consider.

Note: Excess caffeine consumption should be avoided as it can cause symptoms such as insomnia, headaches and irregular heart rate.

Method

This is your instructions for how to complete the experiment

Biology; Biology practicals; KS4 Year 10; Investigating human reaction times

1.	In pairs, decide who is person $1$ (B) and who is person $2$ (A).
2.	Person $1$ should sit on the chair with their non-dominant arm placed on the table and their dominant hand (1.) over the edge.
3.	Person $2$ holds the top of the ruler from $30\space cm$ and person $1$ should hold the ruler with $0\space cm$ (2.) between their thumb and forefinger.
4.	Person $2$ should then release the ruler without warning and person $1$ will have to catch the ruler as quickly as they can.
5.	Record the number on the ruler that is level with person $1$ 's thumb. In the diagram, the recording would be $10\ cm$ . The lower the number, the faster the reaction time.
6.	Repeat steps 2-5 five times for both person $1$ and person $2$ .
7	Now drink a caffeinated drink and wait at least $10\space minutes$ .
8.	Repeat step 6.

Analysis

This is how you would use your data to form conclusions.

1.	Use a conversion table to calculate the reaction time from length.
2.	Calculate the mean reaction time for each person before and after caffeine consumption. $mean\space reaction \space time = {time_1+time_2+time_3+time_4+time_5\over 5}$
3.	Discuss the impact of caffeine on reaction time.

Conclusion

Your results should show that caffeine speeds up a person's reaction time. This is because caffeine causes the release of a hormone known as adrenaline. Adrenaline increases heart rate which sends more blood to your muscles and brain. This makes you more alert and explains why you may now have a reduced reaction time.

Evaluation

If you results do not match the hypothesis that caffeine speeds up reaction time, it is important to consider why. You should identify any anomalous data points and exclude these from your mean calculation.

Experiment 2: Investigating the effect of background noise on reaction time

Experimental variables

Independent variable	$Playing \space background \space noise \space (music).$
Dependent variable	$The \space distance \space caught \space on \space the\space ruler.$
Control variables	$Persons \space dominant \space hand \space should \space always \space be \space used, \newline height \space ruler \space dropped \space should \space always \space be \space the \space same, \newline no \space music\space should\space be\space playing\space before\space the\space experiment,\newline the\space ruler\space must\space be\space dropped \space in\space the\space same\space direction.$

Safety precautions

When carrying out experiments it is very important you consider safety precautions. However, in this experiment there are no significant hazards to consider.

Method

You should repeat experiment one, but instead of drinking a caffeinated drink you should use the radio to play music for background noise.

Analysis

Repeat the same analysis as experiment one but with background noise.

Conclusion

Your results may show that background noise increases (slows down) reaction time. This is because background noise may act as a distraction that prevents you from focusing on the ruler.

Evaluation

You should repeat the same evaluation as experiment one on your new set of data.

Learn with Basics

Length:

Unit 1