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List of top two psychological experiments on attention!
Experiment # 1. Span of Attention – Visual:
At any given moment there are several stimuli in the environment competing for our attention. However, our sense organs can respond to only a limited number of them at the same time. This limit is known as span of attention. The span varies from individual to individual, from sense organ to sense organ, and also according to the nature of the stimuli. The earliest psychologist to be interested in the problem was Sir William Hamilton, who made a very crude experimental attempt to study the problem.
An advance was made on Hamilton’s method by Jevons, the logician. However, real scientific experimental work on the problem was started by J.M. Cattell, who used the tachistoscope for this experiment. After Cattell, a number of experimenters have studied the span of attention under different conditions. Later experimenters have distinguished between span of attention and span of apprehension and also found that span of apprehension is greater than span of attention.
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To determine the span of attention for the following type of Visual stimuli:
1. Single dots
2. Grouped dots
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3. Nonsense Syllables (meaningless combinations of letters)
4. Meaningful words, and
5. Numbers.
A tachistoscope of the falling-door type, exposure cards having the following materials printed on them:
(i) Each set of 3 Cards bearing 3 to 10 single dots. (i.e., 3 cards with 3 dots, 3 cards with 4 dots, etc.). The dots are to be arranged in different patterns.
(ii) Cards with 3 dots in each group ranging from 3 groups to 10 groups (having 3 dots corresponding to a single dot in the earlier set of cards.
(iii) Cards with nonsense syllables having 3 letter syllables to 10 letter syllables, 3 different combinations of letters at each level (3 cards with 3 letter syllables, 3 cards with 4 letter syllables etc.).
(iv) Cards with meaningful words, again ranging from 3 letter words to 12 letter words (different words at each stage).
(v) Cards with numbers ranging from 3 digit numbers to 10 digit numbers (again 3 cards at each stage with 3 different numbers having the same number of digits).
Description of the Apparatus:
There are different types of tachistoscopes. Falling-door type is the one which usually has a fixed exposure time. There are other tachistoscopes which are operated electrically and the exposure is variable and adjustable (camera- shutter types). For the present experiment, the simple falling-door type is adequate.
It consists of a wooden screen with a window in the middle which is covered by a movable falling shutter. This shutter can be closed or opened with the help of a lever which is behind the screen at the top. The exposure time is usually 1/10th of a second. It is sufficient to enable the subject to take a quick glance at the exposed material and at the same time short enough to prevent him from reading or memorising it.
Procedure:
The subject is seated in front of the tachistoscope such that he has a good view of the window. The experimenter sits on the other side of the apparatus keeping the five separate sets of cards with him. The sets are shuffled separately and kept ready for the experiment. The experiment has to be done separately for each of the five sets.
First Set of Cards:
“Observe this window carefully. I will say ‘ready’ and open this window. You will see a card with a number of dots. Try to find out how many dots are there. The card will be exposed only for a short time”.
The experimenter then shuffles the set of cards with single dots and exposes them one after the other, each time giving the ‘ready’ signal. After presenting each card, he makes a note of the actual number of dots as well as the subject’s response. The complete set is exposed once and then exposed for a second time. The subject thus views each card twice and therefore there are 6 stimuli for each level, i.e., 6 exposures for 3 dots, 6 exposures for 4 dots, etc.
After exposing all the cards the experimenter finds out how many times the subject has responded correctly for each level out of the possible 6 times.
Results:
Tabulate the results as follows:
Now we are ready to determine the span. For experimental purposes the span can be defined as the maximum number of dots to which at least 75 per cent of correct responses are made, viz. if a subject responds 100 per cent correctly to three dots, 83.3 per cent to four dots and 66.67 per cent to five dots, his span lies between 4 and 5. The span can now be determined by interpolation between 4 and 5.
Procedure with the Other Sets of Cards:
The procedure for the other sets is essentially the same excepting for the instructions, which are as following:
i. Instructions for Groups of Dots:
“This time instead of single dots you will see small separate groups of 3 dots each. After seeing each card, tell me how many groups of dots are there in each card”.
ii. Instructions for Nonsense Syllables:
“In this series you will see some syllables instead of dots. After seeing each card, write down the syllables as correctly as possible.”
iii. Instructions for Meaningful Words:
“Here on each card you will find a familiar and meaningful word. Try to write down the word you see on each card.”
“In this set, instead of words or dots you will find numbers; as before you will have to write down the number you see”.
After exposing all the sets determine the span in each case as illustrated in the case of dots. The whole experiment can be done in two sessions. Otherwise the subject is likely to get bored and fatigued.
(1) Study individual variations in the span for the different types.
(2) Compare the Spans:
There will be some interesting findings with respect to the differences in the attention spans between single dots and groups of dots. The subject who has a span of 6 single dots may also have a span of 6 for groups of dots though the latter actually includes 18 dots. This is because of the factor of grouping. Each group of dots is responded to as a single stimulus, because of the factor of organisation.
Similarly the span for meaningful words will be usually much higher than the span for nonsense syllables, though both are made up of same number of letters of alphabet. This is because of the factor of meaning and familiarity. In the case of meaningful words and numbers there is apprehension or understanding in addition to mere attention. Furthermore, the factor of familiarity is helpful.
Application:
This experiment has a number of practical applications. A very common illustration is the registration numbers given to automobiles. Usually, automobile numbers do not exceed four digits. This is because the traffic constable would be unable to note down the registration number of automobiles violating traffic rules if the number exceeds four digits. However, the letters of alphabet before the numbers are perceived because they are grouped separately.
Experiment # 2. Distraction of Attention:
When we are attending to some stimulus or work, any noise or other type of disturbance tends to affect the efficiency of our attention. This phenomenon of irrelevant stimuli interfering with our attentive process is called ‘distraction’. Not all stimuli can distract out attention, viz., the ticking of a table clock on our study table does not ordinarily disturb us. Sometimes even strong stimuli do not disturb us when we are prepared for it.
One experiment showed that students working on some problems could, to a large extent, resist distractions of different types by putting in more effort. Baker employing dance music as distractor found that in many instances, the subject did better when music was played. Morgan in his classical experiments proved that subjects can soon get used to a distracting influence, and that often efficiency is lost when distracting influence is removed.
Introspective reports, however, show that subjects feel a greater strain and have to put in greater effort under distracting conditions to maintain the same level of efficiency of attention. Experiments on distraction are usually carried out as group experiments.
To determine the effect of extraneous and irrelevant stimuli on the work efficiency.
A long list of arithmetic problems of uniform difficulty, a sound proof room fitted with number of buzzers, bells, bright lights, etc., to serve as visual and auditory distractions.
The experiment is done under four conditions:
1. Controlled condition.
2. Auditory distraction.
3. Visual distraction.
4. Combination of visual and auditory distraction.
The experiment can be conducted by adopting any one of the following experimental designs:
Experimental Design 1:
Different groups of subjects are assigned to the four conditions.
Experimental Design 2:
The performance of all the subjects under controlled conditions, without any kind of deliberate distraction, is assessed and on the basis of these scores, the subjects are grouped into three matched groups. Each one of these groups is assigned to each one of the three conditions of distraction.
Experimental Design 3:
The performance of each subject is assessed under all the four conditions.
In the first experimental design, the subjects are selected and assigned to the four conditions by following the method of randomisation.
In the second experimental design, the subjects are categorised into three matched groups by following any one of the techniques of matching the groups, and each one of these groups is assigned to one experimental condition by following the method of randomisation.
In the third experimental design the subjects are categorised into four groups by following the method of randomisation and the performance of each one of these groups under all the four conditions is observed. However, the order of presentation of the four conditions should be counter-balanced.
Give the selected arithmetic problems to the subjects and ask them to solve them.
For five minutes allow them to solve the problems under normal conditions, and then ask them to highlight the last problem they have solved.
Suddenly, at the end of 5 minutes, switch on the buzzers and the bells so that the room is filled with loud noises. The subjects have to continue solving the problems. Ask the subjects to indicate the last problem they have solved.
At the end of five minutes switch off the buzzers but switch on the bright lights, flashing glaring lights of different colours and ask the subjects to mark the last problem they have solved.
4. Combination of Visual and Auditory Distraction:
At the end of five minutes, switch on both the buzzers and the lights and ask the subjects to highlight the last problem solved.
Now collect the answer sheets and correct them. Tabulate the number of problems attempted and the number correctly solved for each of the five-minute periods. Take the introspective report of the subject.
Tabulate the results as follows:
Compare the results under the four conditions. See whether work efficiency has, been affected. Analyse the introspective reports to find out the subjects inner reactions to various distractions. Also find out whether they had to put in greater effort to carry out the work under different conditions of distraction.
Tabulate group results as follows:
1. Calculate the Mean & SD under all the conditions for problems attempted as well as problems correctly solved.
2. Do all subjects show the same type of change under distraction?
3. Which condition is most distracting for the group and which the least?
4. Do all the subjects show the same trend of performance under all the four conditions?
It may be interesting to study the effect of preparedness of the subject for distraction.
Instruct the subjects and give them prior information about the occurrence of the distraction. This can be done by giving the instructions for all the conditions at the beginning or specifically before the start of each session studying the effect of a specified condition.
Such experiments are useful in pinpointing factors that distract workers in factories, offices, etc. where the efficiency of the workers can be improved by eliminating the distracting conditions. Industrial psychologists have carried out several experiments on this subject. It has been found that minimisation of noise in the work situation facilitates the employees to concentrate better on their tasks resulting in better output. Further, excess of noise has also been found to lead to stress.