The Stroop Phenomenon

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The Stroop Phenomenon Essay

IntroductionThe stroop phenomenon is a way of measuring how automatic orintentional some well practised tasks are and how we respond in conflictsituations. This phenomenon also measures individual distinctions,originality and cognitive flexibility. The two aspects of cognitivedevelopment that are demonstrated by the stroop task are naming responseand counting response. When two responses compete or are in conflict, thetime required to make the correct decision is dependent on speed andaccuracy. The Stroop Phenomenon Essay.

C. Smith and L.E. Magee; these two researchers found that picturenaming was affected by the presence of incongruent words (Experiment 1).

Also naming a picture was faster than when a congruent word was present.

Therefore pictures activate the name code. Another experiment (Experiment2) indicated that memory for pictures and words, whether they wereinitially named or categorized had an effect on memory. Memory was betterfor words if they have been categorized and for pictures if they have beennamed. Experiment 3 showed the same results as the previous twoexperiments.


The fourth experiment, with the introduction of less commonobjects, subjects could name the words faster than generating a categoryname for the words. Naming pictures are prone to interference whenincongruent words are presented simultaneously. Word naming is not as muchinfluenced by distracting pictures. Pictures and words differ in theamount of information to be filtered out, to get the correct response.

The design of this experiment is a within subject experiment as thenumber of choices to be made after viewing the stimulus on the screen aresame for everybody (2,3,4). Also the meaning versus number choices (same,different, conflicting) are used by everyone. The dependent variables inthis experiment are average accuracy (%) and average time/response (msec).

the independent variable is the random stimulus which appeared on thescreen, whether it was the same, different or conflicting. In thisexperiment we were shown 2, 3, or 4 items on the screen in a randomizedform and had to select the right number of items using 2,3,4 on thekeyboard as quickly and accurately as possible.

In this experiment, the stroop task will be demonstrated. When thereis no conflict between the stimulus and response to be chosen, responseswill be quick and accurate. The Stroop Phenomenon Essay. When there is a conflict between the stimulusand response to be made, interference will exist and responding will beslower and less accurate.

Results & Discussion Figure 1The average accuracy in percent for subject 1, was good for the ‘same’condition. Then they started to decrease when the stimulus was’different’. This score for subject 1 at the ‘different’ condition was thelowest among all 3 conditions. When the stimulus was ‘conflicting’, subject1 was losing accuracy again and so was not as high as in the ‘same’condition. Subject 1 was less accurate in the ‘different’ and’conflicting’ situations.

The average accuracy in percent for subject 2, was quite consistent,being one hundred percent in all conditions. So this subject had a higheraccuracy rate than subject 1. Figure 2In relation to average time/response in milliseconds, subject 1 wasquicker than subject 2. Then condition where subject 1 slowed down themost was in the ‘different’ condition. In the ‘conflicting’ condition,subject 1 increased their speed more than in any other condition.

Subject 2 was quite consistent in all 3 conditions in relation toaverage time/response, with the milliseconds being only 3 or 4 differentfrom the other conditions. For subject 2 the highest responding rate wasin the ‘conflicting’ condition, followed by ‘same’, then the ‘different’condition.

This shows that in the ‘conflicting’ condition, the subjects responserate increased. In the ‘different’ condition the response decreased. Alsoif one subject has a higher accuracy rate than another subject, then theaverage time/response will be lower.

The stroop task demonstrates that the naming response (same) is fasterthan the response used while counting (different) and that when 2 responsesconflict (conflicting), the time to make a correct decision increases.

Since people find the ‘conflict’ condition difficult, they will makemore errors and take more time to determine the correct response. So theaccuracy and response rate decreases in the ‘conflict’ situation.

The difference in speed and accuracy in the 3 conditions (same,different, and conflicting) was the result of the experience with eachspecific condition. The more practice with each condition, the smaller thedifferences in speed and accuracy among the three conditions.

When there is no conflict, people are accurate and quick in respondingto the stimulus. So in the situations of ‘same’ and ‘different’ (22 and**), people will respond by pressing 3 and do well. Subject 1 was leastaccurate in the ‘different’ condition, but was still quicker compared tosubject 2; who was very accurate but not as quick as subject 1. The Stroop Phenomenon Essay.

In the ‘conflict’ situation, where an example of 222 showed up on thescreen and the response was to be 3. In this incident most people havetrouble responding due to interference, which leads to slower respondingand less accuracy. When subject 1 was presented with the ‘conflicting’situation, response was faster than in non- conflicting situations; butaccuracy suffered. Subject 2 was more accurate (100%) but was slower inresponding.

Just as in the research done by Smith and Magee, there was an effectby the presence of an incongruent (conflicting) stimuli. Also when there isa congruent (same) stimuli present, response becomes quick, as there is amuch faster processing rate which occurs. There is also support thatmemory is better for words, in our case numbers and for pictures that aregiven consistent symbols (eg. ***). When responding to the stimulus on thescreen, in ‘different’ conditions, if incongruent stimuli are presentedsimultaneously, there is a chance of disruption. Recognizing the correctnumber of items on the screen is not influenced much by distractingpictures (symbols). In our case this was a problem that Subject 1 washaving, so it is not fully supported.

ReferenceMagee, L.E. & Smith, M.C. Tracing The Time Course of Picture WordProcessing. Methods & Strategies : In Psychological Research, 1991,8, 361-388.

The purpose of this experiment was to investigate the Stroop effect, and the difference in reaction time between the congruent and incongruent conditions. There were 21 participants involved. A repeated measures design was used for the two conditions: congruent and incongruent.The Stroop Phenomenon Essay. Participants were required to look at coloured words and name the ink colour, whilst ignoring the actual word. The results show that reaction time was faster during the congruent condition and fewer errors were made. The level of significance was P<0.001, meaning that the probability of the results being due to chance is less than 1%. This proved both hypotheses to be correct, thus supporting the original Stroop investigation (1935).

The process of ‘attention’ requires the cognitive ability of an individual to selectively concentrate on a certain stimuli in the environment whilst selectively ignoring others. However, if attention is diverted by interference from another stimulus. Interference became very influential in cognitive and neural components of selective attention and was the basis for much research prior to Stroop.¹

The Stroop effect was originally named after John Ridley Stroop and was published in 1935. The test demonstrates the difference in reaction time of naming colours, reading names of colour, and naming colours of words printed in different ink. It also aims to measure cognitive ability (learning and memory) and attention focus.² Thus it can be argued that the word and its meaning can be processed even though it is not relevant.

In ‘Stroops classic article’, he raised two questions: what effect each dimension of the different stimuli would have on naming the other dimension i.e. colour ink and the word itself. Secondly, what effect practice would have on the reaction time to both stimuli. Given this, he conducted two experiments. Experiment 1 investigated the effect of different ink colours on reading the words out aloud. The second experiment focussed on reading the colours aloud. Results showed that participants took approximately 47 seconds longer to name the colours of the incongruent condition as opposed to the coloured squares. Stroop concluded that this 74% increase was due to an interference effect.³

Stroop’s research originated from James McKeen Cattell (1886), who found that responding to objects and colours took longer to read aloud than words. The association between the name and idea took place so frequently that it became an automated process. Unlike with pictures and colours, an intentional effort had to be made.4

The Stroop effect was used to discredit the theory of controlled and automatic processing by Schneider and Shiffrin (1977). Their theory concluded that controlled processing was slower than automatic. Also, once a task was automated it could be done with no conscious effort, and this would affect all other activities.5

Sheibe, Shaver and Carrier (1967) found that if the word was congruent, it would be identified quicker than if it was incongruent. This also supports for Stroop’s investigation (1935).

However, all prior researchers were interested in studying the interference between conflicting processes and none thought to combine colours and words until Stroop. The Stroop Phenomenon Essay.

Since Stroops original experiment, there have been many variations made to test different phenomena. For example, sorting and matching versions of the colour word task, the picture-word interference task, and the stroop colour-word test.6

The aim of this experiment is to prove Stroops theory, and to investigate how interference affects participants’ ability in both conditions

Hypothesis 1:

The reaction time for the congruent condition will be significantly faster than that of the incongruent condition.

Hypothesis 2:

Fewer mistakes will be made within the congruent condition in comparison to the incongruent condition.

A repeated measures design was used for this experiment. This requires using the same participants for each condition – congruent and incongruent. This allows the responses from an individual for the congruent condition to be directly compared to their response for the incongruent condition.7

There were two conditions being compared. The congruent condition consisted of words written in the same colour ink e.g. the word ‘red’ was written in red ink. The second condition was incongruent e.g. ‘red’ written in blue ink.

A sample of 21 Psychology students from Royal Holloway University of London participated, aged between 18-21; 16 females and 5 males. However, 12 were excluded due to there being no response, or their responses were excluded.

A computer was used to generate the two stimuli and collect the participants’ response. The program used was ‘DMDX’ and involved participants to respond to the ink colour of written words, whilst ignoring the word. The words were displayed in the centre of the screen for approximately 750ms. Before each word, a fixation point (+) was presented in the centre of the screen before the next word. The interval between the fixation point and the next word also lasted 750ms. There was also an ‘inter-stimulus interval’ (ISI) of 2000ms between fixation and word presentation.

The procedure of the experiment was followed in two parts. During part 1, participants were asked to follow instructions and confirm their gender. This allowed information to be gathered about the participants so that analysis could be carried out later about whether or not the sample used was bias. In Part 2, the participants were given 9 trial runs, 4 congruent and 5 incongruent. Participants were then asked to view the fixation point (+) which was followed by words displayed in different coloured ink and were asked to indicate the ink colour. The following keys were used to indicate the chosen colour: 1 – red, 2 – green, 3 – blue, 4 – yellow. In total the participants were asked to carry out 200 trials for 5 minutes. Each condition consisted of 100 trials – 25 of each colour. The responses from each participant for each condition were generated into a database.

Participants: 5 males and 16 females. Total: 21

Descriptives: mean age: 20.14 (6)

Descriptives: Table
The results table show that the mean reaction time and (standard deviation) for the congruent condition was 732 milliseconds (189) and 860ms (232) for the incongruent condition. The Stroop Phenomenon Essay. This shows that the reaction time for the congruent was faster than the incongruent condition, thus accepting the alternate hypothesis. The mean error and (SD) for the congruent condition was 5 (3) and 10 (6) for the incongruent condition.

RTs t-test (p value): t(20) = 8.34, p = <.001

Errors t-test (p value): t (20) = 4.82, p = <.001

The chosen statistical analysis was a t-test. This allows us to compare the results in terms of reliability as the t value obtained is related to a specific value for the degrees of freedom for the experiment. The calculated t value at the confidence level of p=<.001 is less than the value predicted for the p value. This allows us to reject the null hypothesis and accept the alternate as the results obtained can be said to be 99% concurrent due to the independent variable.

The results from this experiment illustrate that the reaction time for the congruent condition was significantly faster than that of the incongruent condition, as seen in fig 1. After the standard deviation for ‘error’ was calculated, it can be seen that the incongruent condition had significantly higher error values in comparison to the congruent condition (see fig 2). This supports both hypotheses and therefore proves the Stroop effect (1935), where participants were placed in two different conditions. The participants that were assessed in the congruent condition were found to have significantly lower reaction times when naming the colour of the ink in comparison to those in the incongruent condition. The theory of Sheibe, Shaver and Carrier can also be applied to our results as it has been proven that interference does occur via automatic processing. Their research also proved Stroops work as they found that if the colour word was written with the same colour then the time to state this by the participant was notably faster in comparison to words that used different coloured ink. This then gave way for research to be performed in regards to stimuli response as later research found that there was less interference when the stimuli was similar e.g. the word blueberry is already associated with the colour blue and therefore this would have less interference than for example the word apple. The Stroop Phenomenon Essay.


Limitations and Further research
The main problem encountered was the sample bias. The participants that were used were all psychology students from university, and cannot be generalised to society. Therefore the results gained are unreliable. The experiment can also be heavily criticised for being gender bias, as there were only five males in comparison to sixteen female participants. This also had a confounding affect on the results as shown in fig 1 and 2, as male participants had a faster reaction time than females. Therefore we cannot generalise our findings as the sample used was not equal.

Another limitation was the effect the uncontrolled variables had upon the investigation such as noise and light which acted as interference and could have affected the reaction time and number of errors.

Improvements are required to increase the validity of the results. A larger sample size would make this experiment more reliable and more able to generalise the findings. To improve this aspect further, a wider age range would increase the validity as age could have an affect on attention. This could be used to research further into the mind of individuals. Furthermore, a more diverse gender would be beneficial in increasing the validity of the experiment as there are key differences between male and females as has been indicated throughout the field of psychology. In order to develop this investigation, interference can also be measured aswell as reaction time. This would produce results of a higher accuracy, increasing the validity. However, this would require the external environment to be adapted accordingly, thus elimin ating any extraneous variables that could alter the results. The Stroop Phenomenon Essay.