Introduction:
Reaction time is a measure of how quickly an organism can respond to a particular stimulus. Many researchers have confirmed that reaction to sound is faster than reaction to light, with mean auditory reaction times being 140-160 msec and visual reaction times being 180-200 msec (Galton, 1899; Woodworth and Schlosberg, 1954; Fieandt et al., 1956; Welford, 1980; Brebner and Welford, 1980). An auditory stimulus only takes 8-10 msec to reach the brain (Kemp et al., 1973), but a visual stimulus takes 20-40 msec (Marshall et al., 1943).
Differences in reaction time between these types of stimuli persist whether the subject is asked to make a simple response or a complex response (Sanders, 1998, p. 114).
Reaction time has been widely studied, as its practical implications may be of great importance to every day events, such as response time when driving a car. Many factors have been shown to affect reaction times, including age, gender, physical fitness, fatigue, distraction, alcohol, personality type, and whether the stimulus is auditory or visual. A question you may wish to think about is why do we process sound faster than sight. It is worth noting how we respond to sound. We have all set through a horror movie only to be startled by a loud sound. In the dark you are less likely to jump out of your skin at the sight of a shadow approaching you as you are by a loud noise near by. We have evolved to react quicker to sounds than to sight. After all, something making a loud sound near by is more threatening than viewing the threat from a distance. If someone were to shine a bright light in your eyes, it would be less likely to make you jump instinctively than if someone made a loud noise
When viewing the threat we take in a great deal of information and consequently spend time processing it. Just like a cat trapped in head lights.
The model for information flow within an organism can be represented in this way:
Stimulus => Receptor => Integrator => Effector => Response
More specifically, in vertebrates, information flow can be represented in this way:
Stimulus => Sensory Neuron => Spinal Cord or Brain => Motor Neuron => Response
Sensory neurons convert a stimulus into an electro-chemical signal, which flows the length of each neuron(s) Generally, motor neurons will cause a muscle to contract or a gland to secrete a substance. Reactions that involve only the receptor, the spinal cord, and the effector, are faster than those which involve processing in the brain. Reactions which only travel to, through, and from the spinal cord are often called spinal reflexes or cordmediated reflexes. Withdrawing one’s hand from a hot stove is an example of such a reflex. In simple reaction time experiments there is only one stimulus and one response. Catching a dropped stick, or hitting a button when a light changes are examples.
In recognition reaction time experiments, there are symbols to respond to and symbols to be ignored. There is still only one correct stimulus and one response. An example would be catching a dropped stick with a word cue, while having to ignore other spoken words which are not cues.
In choice reaction time experiments, there are multiple stimuli and multiple responses. The reaction must correspond to the correct stimulus. Typing a letter which matches a printed letter prompt is an example of this type of experiment. |
Methods:
Four methods will be discussed here, three involve catching a dropped ruler; the other is computer based and involves moving and clicking a mouse in response to a particular stimulus.
Click to see another software to measure reaction times.
Ruler Catching Methods: One way we can test reaction time in the lab is by measuring the time it takes to catch a ruler dropped by a second person, prac partner..
Method 1 -- Simple Reaction Time
1. Subject should hold out the chosen hand and extend the thumb and index finger so they are 8cm apart.
2. The prac partner holds a metric ruler with its end exactly even with the subject’s extended thumb and index finger. The ruler should be vertical with lowest numbers near the subject’s hand.
3. The ruler is dropped, and the subject grasps it between the thumb and index finger.
5. Record the number at the subject’s fingertips, i.e. distance the ruler fell through the subject’s
fingers.
6. Calculate the time it took for the subject to react and catch the falling ruler. The time it took for the ruler to fall can be calculated from the distance it fell. Distance (d) fallen can be converted to time (t) passed with the following formula:
d (in cm) = (1/2)(980 cm/sec2)t2
t2 = d/(490 cm/sec2)
t = √d/(490 cm/sec2)
[980 cm/cm/sec2 is the acceleration of a falling mass on Earth. Since we know how fast an object falls, we can figure out how long it took to fall a measured distance.]
Methods 2: Reaction Times with a Word Cue: This method will once again calculate reaction time by calculating the time it takes to catch a dropped ruler, but in this method a final word cue is given, as well, after other words are spoken that should be ignored.
1 and 2. Exactly the same as in Method 1.
3. Determine a particular word as a signal to catch the dropped ruler.
4. Use a variety of words before dropping the ruler; disregard ruler catches on wrong word.
5. Record the number at the subject’s fingertips, i.e. distance the ruler fell through the subject’s fingers,
6. Calculate reaction time in seconds as in #6 above.
Method 3 – Reaction Time with Word Association
1 and 2: Exactly the same as in Method 1 and 2.
3. Say a stimulus word as a signal to catch the dropped ruler. Do not predetermine the stimulus word. The subject will catch the ruler with any word as a cue. This time, however, the subject must also respond with a word. Keep a record of catches that do not count because of the lack of a word association.
4. Subject responds with a word and catches the ruler while responding. If unable to make a word association, the catch does not count.
5. Record the number at the subject’s fingertips, i.e. distance the ruler fell through the subject’s fingers.
6. Calculate reaction time in seconds as before.
Method 4: This is a choice reaction time test which tests how fast you can respond to the
random appearance of dots in a grid over the course of 30 seconds. Click to see it.
With these tests and the population of subjects you have available, ask some questions about reaction time you can test..
Design an experiment to help answer one of your questions. You may discuss this with your teacher.
In your experimental plan consider the following
1. Justification for your questions: why is it interesting or what makes it applicable to a real problem ?
2. State the hypothesis you are testing.
3. What is your Independent variable ?
4. What is your dependent variable?
5. What type of data will you be collecting?
6. What type of statistical analysis will you use?
7. What type of graph will you use to present the results ?
8. How many subjects will you use?
9. What is the predicted outcome if your hypothesis is true ?
10. How will you control your independent variable?
Results:
Describe your data and descriptive statistics here. Any graphs can be included here as well.
Describe anything that is particularly interesting or noteworthy, such as trends you notice, about the data here, but do not
make any interpretations or conclusions.
Conclusions:
Interpret your results here, and address the following questions.
Were you able to answer your question with the data you collected?
Does the data support or refute your hypothesis?
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An example
Devise a question - Is having a conversation detrimental to reaction time? This is particularly important in the debate on banning mobile phones while driving.
Hypothesis - Focusing on the verbal communication should increase the time required to react to a particular stimulus.
Independent variable - verbal communication with subject
Dependent variable -reaction time
Type of data collected- length, in cms, the ruler fell before catching
Analysis of data - data will be averaged for no communication and verbal communication and compared
Type of graph - bar graph
How many subjects- 30
Controlling the independent variable - subject will be asked to verbally communicate with examiner through a number of tests, then the same tests repeated in complete silence.
Method 3 and method 4 can be applied for this investigation.
Another question that can be studied
Do Humans react to sound faster than sight? This is particularly important in events such as the Olympics or fire alarms and pedestrian crossings. |
Galton, F. 1899. On instruments for (1) testing perception of differences of tint and for (2) determining reaction time. Journal of the Anthropological Institute 19: 27-29.
Kemp, B. J. 1973. Reaction time of young and elderly subjects in relation to perceptual deprivation and signal-on versus signal-off condition. Developmental Psychology 8: 268-272.
Marshall, W. H., S. A. Talbot, and H. W. Ades. 1943. Cortical response of the anaesthesized cat to gross photic and electrical afferent stimulation. Journal of Nerophysiology 6: 1-15.
Sanders, A. F. 1998. Elements of Human Performance: Reaction Processes and Attention in Human Skill. Lawrence Erlbaum Associates, Publishers, Mahwah, New Jersey. 575 pages.
Woodworth, R. S. and H. Schlosberg. 1954. Experimental Psychology. Henry Holt, New York. |