The stroop effect is a cool little thing my professor showed us in abnormal psychology here at the College of Wooster. What the stroop effect does is show how words can get in the way of perceptions. It was first reported in 1935 in the Journal of Experimental Psychology by John Ridley Stroop.

What we did in class differs slightly from Stroop's original experiment. In class, the professor showed us four squiggles, each a different color, blue, green, red and brown. The colors themselves don't matter too much, any four will do. He had us say the name of the color of the squiggle he pointed to with his pen aloud. He also did this with the following slides. The next page he showed us was similar, it contains groups of 3-6 jumbled letters, broken up as if they were words, in the four different colors. A third slide was then shown, using actual words colored in one of the four colors (each word was a different color). The fourth slide was the kicker, it was the word versions of the four colors, all in a different color than the word they spelt. Red would be in blue, blue in brown, etc. When the class tried to read these aloud, we all failed. No one in the class could read the color of the word without confusing it up with the word that was colored. This is believed to be due to the Automatic word recognition hypothesis.


Liveforever suggests this link, http://faculty.washington.edu/chudler/wo rds.html, instead of the previous one here, as that one no longer worked

Report

Abstract

The aim of the experiment was to look at the cognitive processed behind automisation and how it is studied in psychology, looking at the experimentation used (namely Stroop effect) for the most part.

The hypothesis being worked to was "there will be a significant difference in participants information processing times under two conditions as a consequence of the Stroop effect." and thus the null hypothesis is that "there will be no significant difference in participants information processing times under two conditions described by the Stroop effect."

The research was carried out within a college on 20 volunteers who were subjected to the Stroop effect test. Graphical representation of the data was extracted as well as a spearman's rho. When asked to read the ink colours of a list of neutral words the participants took less time on the whole than when asked to read the colour of colour words.

Introduction

Cognition is
'A concept of human and animal learning which holds that both humans and animals acquire items of knowledge known as cognition, such as what is where ( cognitive map ) or what leads to what (expectancy).'
Basic Psychology, Glietman, Fourth Edition,1996.

Therefore it is thought that once learned you will then store that information and use it when needed. So in reflection when you are first learning to drive a car, you will find it almost impossible to find the balance between the clutch and the accelerator, but when learned, you find that you will do it automatically without have to think about it, the behaviour or skill seems to no longer require direct interaction. Much behaviour become automised in daily life such as, typing, cycling and writing.

Some things, which we learn, are far more impressed on us than others. We also find that when two pieces of information are connected to one thing that although we may automatically process both, when it comes to trying to separate them it is rather hard, this is interference. Many experiments have been used to look into automated behaviours especially because of the fact that some automated behaviours are undesirable. To study the methods behind their processing, simple tests, such as Stroop may be used.

Stroop's tests in 1935 were based on getting a participant to look at words such as for example "red" printed in blue ink. He noted that this caused a person to halt or falter slightly, because the word was interfering with the colour. The thought behind this is that reading is an automated process and is faster to be taken in thus when a person tries to read the colour of the ink there is "interference" and it thus takes them longer.
"The Stroop task, and it's many variations, are a commonly used tool in cognitive psychology to explore how different types of behaviours interact."
(http://www.msu.edu/course/psy/403/Stroop/psy403s03Stroop.htm) Because of this there have been several times in which it has been used for major experiments. Many have slightly altered the original version, suiting it to their own purposes and making it a little more effective along the way.

In 1985 for example, Virzi and Egeth looked at the neuropsychological model of the Stroop effect, looking at the processing which must occur and finding that a verbal response to the Stroop test, meaning that the brain had to process the information so it was able to be produced verbally, the reasoned that this was why there was a slightly delayed response time.

In this piece of research, there is the aim to investigate interference using pairs of conflicting stimuli on serial verbal reactions. What we percieve as being the result is that
"there will be a significant difference in participants information processing times under two conditions as a consequence of the Stroop effect." The null hypothesis is that "there will not be a significant difference in participants information processing under the two conditions" We are using the Stroop effect as it involves the repeated measures design, useful for testing dual hypotheses and minimising the effect of variables.

Design

The repeated measures design was used for this experiment, which is good when you have such a piece of research that may be affected by many variables. The problem with this method is that a person may "learn" how to do it due to the repetitive nature of the experiment. This is known as the order effect but is counterbalanced with half of the subjects starting with the neutral lists (1-3) and half starting with the non-neutral lists (4-6) The participants were read a set of instructions which had been pre-written so that each had the same introduction and thus any extraneous variables there were excluded. The participants were tested for colour blindness or reading difficulties to this end also. The participants were chosen with random opportunity sampling. Ten females and ten males were randomly chosen by two of the researchers who also waited with the volunteers who had not yet taken part, disallowing them to speak to those who were leaving.

Materials
Colour blindness test
Reading test
Stopwatch
Results sheet
Three lists of neutral words
Three lists of colour words
A pre-written instruction card

Method

The experiment was set up much like the original stroop effect but with a few modern variations. 20 participants were collected, ten male and ten female, using the "opportunity sampling" method, asking people who were around the test area with the only restriction being a 10/10 male to female split. They were taken one at a time into the experimental room, which excluded the others from seeing what might be going on. As they entered the room, the subjects were greeted by the researchers to put them at ease and were asked to sit at a seat in front of a table. The participants were told they were taking part in a piece of psychological research and asked if they were sure they wished to participate.

The subject was then tested for both reading difficulties (with a relatively simple poem) and colour blindness (via the plates developed by Ishihara.) The necessity of this was proved when two colour blind and two people with reading disabilities were found. They were told of the experiment, the situation and why they would thus be unable to participate. They were asked if they wished further information and thanked for volunteering. Due to the fact that several groups were doing the experiment within the same area the participant was also asked whether or not they had already taken part in the experiment in which case they would be unable to participate.

Once it had been ascertained that the subjects were able to participate fully in the study they were then read the instructions as follows :

"I am going to present you with six lists of words, one at a time. Your task is to say aloud the ink colour in which each word is written, starting at the top of the list and working your way to the bottom. You will be timed for each list and should try to name the ink colours as quickly but as accurately as possible. Do you have any questions ?"

The participants were allowed to ask anything they were unsure of and once their questions were answered they were told :

"Here is the first list... when I turn the list over, name the ink colour in which the lists are written."

The subject was given one list at a time by the researcher and timed as soon as the list was placed face up towards them on the table. This was repeated with the other five lists, the time taken for each one noted down.

Once they had completed the test, they were told what the experiment was about, and allowed to ask any questions they might have. They were then thanked for taking part and allowed to leave.

For five males and five females the lists 1-3 were used first and then 4-6 for the other half, the 4-6 lists were used first, the 1-3 lists used secondarily. The reason for this was to hopefully prevent or be able to distinguish whether they were getting better by the non-neutral words (lists 4-6) because of the fact that they had practiced on the neutral words lists (1-3)

Results

For those who names "neutral" words (lists 1-3) first.

           List 1 List 2 List 3 List 4 List 5 List 6 

Subject 1  9.6    7.61  9.69   12.41  11.64  9.84 

Subject 2  7.81    7.61  10.00  12.90   9.97  11.27 

Subject 3  12.43   8.62  10.67  16.57  10.52  10.72 

Subject 4  11.11  11.83  14.41  23.72  18.46  19.96 

Subject 5  11.71  14.67  13.47  23.92  15.65  17.35 

Subject 6  16.49  17.12  14.69  16.44  12.63  13.12 

Subject 7  11.34   7.78   7.01  18.72   8.25  10.96
 
Subject 8 10.33  10.49  11.42  16.99  14.12  16.68 

Subject 9  8.73    7.98   8.43  12.99   9.41  14.08 

Subject 10 11.72   9.63   9.77  16.92   9.94  12.67 

Subjects 1-5 are female
Subjects 6-10 are male

For those who names "neutral" words (lists 1-3) first.

           List 4 List 5 List 6 List 1 List 2 List 3 

Subject 11 31.59   15.66 18.57   14.45  11.33 13.60 

Subject 12 21.93   15.70  18.64  17.53  17.29  16.00

Subject 13   9.20   9.10   7.85   8.45   6.40   7.95

Subject 14  25.95  14.62  19.67  14.35  17.86  14.01 

Subject 15  11.87  11.80  15.55   8.52  10.61  14.99 

Subject 16  22.09  16.19  22.17  18.07  16.71  17.60 

Subject 17  20.41  10.54  11.51  13.12   8.45   9.40
 
Subject 18 17.37   15.52  15.79  11.77  9.32   9.82

Subject 19 22.58   20.87  20.53  14.29  12.68  13.67 

Subject 20 9.33   9.67   9.59   7.59   9.72    8.58

Subjects 1-5 are female
Subjects 6-10 are male
In this spearman's rho, the subjects individual times for lists 1-3 (rank x) have been totalled; as well as their times for lists 4-6 (Rank Y)
           Lists 1-3  Lists 4-6  RankX  RankY  D  D2
Subject 1  26.9       33.89       5      5     0  0
Subject 2  25.42      34.14       2      7    -5  25
Subject 3  31.72      37.81       8      9    -1  1
Subject 4  37.35      61.87      10     20    -10 100
Subject 5  39.85      56.92      12     19    -7  49
Subject 6  48.30      42.19      14     14     0  0
Subject 7  26.13      37.93       3     10    -7  49
Subject 8  32.24      47.79       9     16    -7  49
Subject 9  25.14      36.48       1      8    -7  49
Subject 10 31.12      39.08       7     11    -4  16
Subject 11 65.82      39.38      20     12     8  64
Subject 12 56.27      50.82      16     17    -1   1
Subject 13 26.15      22.80       4      1     3   9
Subject 14 60.24      46.22      17     15     2   4
Subject 15 39.22      34.12      11      6     5  25
Subject 16 60.45      52.38      18     18     0   0
Subject 17 42.46      30.97      13      4     9  81
Subject 18 48.68      30.91      15      3     12 144
Subject 19 63.98      40.64      19     13     6  36
Subject 20 28.59      25.29       6      2     4  16
                                          Total = 718
SR = 1 - 6x718 / 20 x 399  = 1 - 4308 / 7980  = 1 - 0.54 = 0.46
These results show a low correlation between lists 1-3 and lists 4-6
Part 1
Grouped frequency tables - Lists 1-3
Class  Class Intervals    Class Frequency
1      5- 7.99           6
2      8-10.99           10
3      11-13.99          8 
4      14-16.99          4
5      17-19.99          2  
6      20-22.99          0 
7      23-25.99          0
         ___
  10|   |   |
    |   |   |
  9 |   |   | 
    |   |   |___
  8 |   |   |   |
    |   |   |   |
  7 |   |   |   |   
    |___|   |   |   
  6 |   |   |   |   
    |   |   |   |    
  5 |   |   |   |   
    |   |   |   |___
  4 |   |   |   |   |   
    |   |   |   |   |   
  3 |   |   |   |   |   
    |   |   |   |   |___   
  2 |   |   |   |   |   |
    |   |   |   |   |   |
  1 |   |   |   |   |   |
    |   |   |   |   |   |
    _____________________________
    | 1 | 2 | 3 | 4 | 5 | 6 | 7 |


Grouped frequency table lists 4-6
Class  Class Intervals    Class Frequency
1      5- 7.99           0
2      8-10.99           8
3      11-13.99          8
4      14-16.99          8
5      17-19.99          4  
6      20-22.99          0 
7      23-25.99          2
         
  9 |     
    |    ___ ___ ___
  8 |   |   |   |   |
    |   |   |   |   |
  7 |   |   |   |   |
    |   |   |   |   |
  6 |   |   |   |   |
    |   |   |   |   |
  5 |   |   |   |   |   
    |   |   |   |   |___ 
  4 |   |   |   |   |   |
    |   |   |   |   |   |
  3 |   |   |   |   |   |
    |   |   |   |   |   |    ___
  2 |   |   |   |   |   |   |   |
    |   |   |   |   |   |   |   | 
  1 |   |   |   |   |   |   |   |
    |   |   |   |   |   |   |   |
    _____________________________
    | 1 | 2 | 3 | 4 | 5 | 6 | 7 |

Part 2
Grouped frequency table lists 1-3

Class  Class Intervals    Class Frequency
1      5- 7.99           3
2      8-10.99           9
3      11-13.99          6 
4      14-16.99          7
5      17-19.99          5  
6      20-22.99          0 
7      23-25.99          0
         ___
  9 |   |   |  
    |   |   |
  8 |   |   |
    |   |   |    ___
  7 |   |   |   |   |
    |   |   |___|   |
  6 |   |   |   |   |
    |   |   |   |   |___
  5 |   |   |   |   |   |
    |   |   |   |   |   |
  4 |   |   |   |   |   |
    |___|   |   |   |   |
  3 |   |   |   |   |   |
    |   |   |   |   |   |
  2 |   |   |   |   |   |
    |   |   |   |   |   |
  1 |   |   |   |   |   |
    |   |   |   |   |   |
    _____________________________
    | 1 | 2 | 3 | 4 | 5 | 6 | 7 |

Grouped frequency table lists 4-6
Class  Class Intervals    Class Frequency
1      5- 7.99           1
2      8-10.99           6
3      11-13.99          3
4      14-16.99          7
5      17-19.99          4  
6      20-22.99          7 
7      23-25.99          1
8      26-28.99          0
9      29-31.99          1
         
  9 |     
    |   
  8 |   
    |            ___     ___
  7 |           |   |   |   |
    |    ___    |   |   |   |
  6 |   |   |   |   |   |   |
    |   |   |   |   |   |   |
  5 |   |   |   |   |   |   |
    |   |   |   |   |___|   |
  4 |   |   |   |   |   |   |
    |   |   |___|   |   |   |
  3 |   |   |   |   |   |   |
    |   |   |   |   |   |   |
  2 |   |   |   |   |   |   |
    |___|   |   |   |   |   |___     ___
  1 |   |   |   |   |   |   |   |   |   |
    |   |   |   |   |   |   |   |   |   |
    _____________________________________
    | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |


Discussion

As the theory was that the non-neutral words would take a longer time to be processed due to interference, we can say it has been proven. The fact that the results could be different depending on if the participants read the non-neutral words before the neutral words was also shown, with those who read the non-neutral sets (lists 4-6) first taking a little longer than those who had read the neutral lists first. This has showed that the design of the experiment was effective, taking a balance of both into consideration.

The number of students used was effective in showing the trends but because of the limited number of students there cannot be a widespread comparison. The experiment, because it used college students. If the study had been larger and contained more people generalisations may have been able to be made, though the methods used were suitable mainly for a smaller test population.

The room used was relatively private and excluded variables which might have otherwise affected the results such as noise etc. These might have taken concentration off of the task at hand but this problem was eradicated. At the time of the test, there were only ever two of the researchers present in the room to both avoid pressure and distraction, this was more advantageous too, because of the small size of the room.

Conclusion

The research was carried out in an effort to find out whether the hypothesis that "there will be a significant difference in participants information processing times under two conditions as a consequence of the Stroop effect." was true. Due to the results gained we have shown this to be correct as well as also showing that there was no direct correlation between gender and a difference in the results . The null hypothesis, that there would be no effect on the time under the two conditions of the Stroop effect was disproved. It can thus be concluded that the Stroop effect is applicable (at least for the population tested) in the way it has been used for previous studies and the results the researchers in this case gained were concurrent with those previously done in this field of research.

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