The Interference of Stroop Effect on Colours and Words

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The major focus of this experiment was to study and run an investigation how changing or matching the font color of a given stimulus word towards the color named by the word would affect the time to react when identifying the font color of these words. This is called the stoop effect one of the fundamental phenomenon that is commonly used in cognitive psychology. In other words this experiment would purposely investigate the existing difference in the time taken to react towards either incongruent conditions or congruent conditions. The participants were required to identify the color of the words present not paying any attention to the actual word. However the time taken by the participant to give a response at every step was recorded in ms. There after a hypothetical test using the t-test method was carried on the collected data to proof the fact that the reaction time during the congruent condition was actually faster.

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The concept of Stroop effect was effective in the year 1935 by John Ridley Stroop basically from the automatic process theory. This theory was concerned with how the processing activities would automatically propagate as a result long-term practice or involvement, at some point response towards such activities would be faster, with less attention and they are not easily avoided (Crank, 1973). According to Stroop the activities such as identifying the word and their associated color was also a form that relied on the automatic process. Therefore the stroop effect was actually a test that demonstrated the distinction or change in time of reaction towards naming the colors, reading the colors of the names and naming the colors of the words painted in different colors (Weiner, 2003). The key aim or objective of the stroop effect experiment was to identify the cognitive ability as well as the attention focus based on the memory and the learning.

The cognitive ability for a given individual particularly for concentrating on a given stimuli in the surroundings while not paying any consideration to the others is a fundamental element of attention. The basis of the research around the Stroop effect was the fact that if interference can divert the attention of a given individual from a given stimuli then interference is effective and can impact the neural or cognitive components of discriminatory attention. Stroop used two theories to explain the basis of the Stroop effect; Speed of Processing Theory and the Selective Attention Theory. According to the Selective Attention Theory interference would normally take place since the process of naming colours calls for a great level of more attention than just reading these words. On the other hand the Speed of Processing Theory points out that interference can easily occur just because the process of reading words is faster than the step of naming the colours. Similarly would this different dimension of stimuli have an impact on the reaction time or the response speed? These were some of the question that Stroop based on to carry out his research and the stroop effect experiments.

The origin of the stroop effect experiments was the Schneider and Schifrin (1977); the controlled and automatic processing theory. According to the two, automatic form of control was faster than the controlled processing. Therefore if a given activity is automated it would tend to take place or happen with little or actually no conscious effort. On the other hand according to Sheibe, Shaver and Carrier (1967), it was an easier task to make an identification of a congruent word compared to the incongruent words. This was concurred with point of view in the investigation done by Stroop (1935). However much had been done and researched on the key relationship among these contradictory processes, but it was actually Stroop that brought in the element of combining the colours and words, thus Stroop effect. He considered the ability of people against reading colour names and naming the coloured words. Stroop (1935) made a reliable conclusion that there is an effect of interference that impacted the participants especially on the time they took to complete the task (Weiner & Craighead, 2010).

As far as this experiment is concerned the analysis would be done using a hypothesis testing method of the T-testing approach to proof that actually according to Stroop (1935), there is an existing interference that impact the respond especially in incongruent situations compared to the congruent situation. This form of data analysis would require the experimenter to generate the mean and the standard deviation value related to the response time in milliseconds. In this analysis a 0.10 significant level was considered. The However from these values the T-test would then be done in order to commit reliable conclusion based on the formulated hypothesis.

There are two forms of hypothesis considered in this analysis: the null hypothesis and the alternative hypothesis.

The Null hypothesis states that, the reaction time for the congruent and the incongruent situation were the same (µ1-µ2) = 0.

The Alternative hypothesis states that, the reaction time for the incongruent situation was higher than the reaction time for the congruent situation (µ1-µ2) ?0.

The hypothesis in place is compost of a two-tailed test; therefore once the mean value is test to be either much bigger or smaller than the then the null hypothesis is rejected (Dodd, Michael, 2001).


The design that was considered in this experiment was a repeated measure with two variables in place; the stimuli A and stimuli B. The two stimuli all had a mixture of congruent and incongruent aspects. The stimuli A in this case had 30 congruent words will stimuli B had 30 incongruent, stimuli A could be considered as  the uncontrolled experiment where the names of the words bared their associated colour while the stimuli B was the controlled experiment where the names of the wordings was different from the colours they bared. Each of these stimuli had 30 variables and the two were presented for testing within 51 participants. The researcher or the experimenter was expected to carry out both the stimuli A and B on each participant where the response or reaction time at each stimulus for both the congruent and incongruent was recorded in seconds.


Fifty one undergraduate students from college willingly volunteered to take part and participated in this laboratory practical. All of those who participated in the experiment were situated within the same stimuli or environment and taken through the exercise by the experimenter. However the participants considered for these exercise were strictly over 18 years of age in mixed gender without any discriminations such as their nationality. As far as the statistics is concerned the average age of the fifty one participants was 36.56 years at a standard deviation of 9.30911. The youngest among the participants was 19 years of age while the eldest participant was 64 years.  However the time taken by each participant to respond or react to a given stimuli was keenly record and the participant were encourage to proceed in case they failed to respond at a given point.



The apparatus that were used for the success of this experiment included a personal computer to run the stimuli and a projector to display the same to the participants. The response time of each participant was recorded using a stopwatch. However the collected data was analyzed using the SPSS software.


The participants were taken through the instruction before starting the laboratory process and test individually. Each of these participants was provided with the two list; stimuli A and B containing 30 stimuli each. The participants were requested to give a response to each and every stimulus as quickly as possible by specifying the colours of the words presented on the projector. The response time taken by each participant to react to both the congruent (Stimuli A) and incongruent (Stimuli B) were recorded.


The response or the reaction time in Milliseconds (Ms.) for each participant for both the congruent and incongruent situation was collected and some of the outcomes of the erroneous response were removed to make a reliable data for analysis. However the mean values and the standard deviation for each set of data were clearly analyzed and presented using the SPSS statistical tool. From the analysis the mean value obtain for congruent situation (Stimuli A) was 21.6157 and for the incongruent situation (Stimuli B) was 35.004. On the other hand the standard deviation value for congruent situation was 7.6833 and for the incongruent situation it was 9.04817.

The table below shows the data analysis for the standard deviation and the mean values for both the congruent and incongruent experimental situations.

The graphical representation for the above analysis is as shown below for both the mean and standard deviation values.


Computing the standard error (SE), the degree of freedom (DF) as well as the t-test value (t).

SE = Sqrt[(S12/N1) + (S22/N2)]

Where; S1=7.6833, S2=9.04817, N1=51 and  N2=51

SE = sqrt[(7.68332/51) + (9.048172/51] = sqrt(1.1575 + 1.6053) = sqrt(2.7627) = 1.66216


DF = (S12/N1 + S22/N2)2 / { [ (S12/ N1)2 / (N1 – 1) ] + [ (S22 / N2)2 / (N2 – 1) ] }

DF = (7.68332/51 + 9.048172/51)2 / { [ (7.68332/ 51)2 / (51 – 1) ] + [ (9.048172 / 51)2 / (51 – 1) ] }

DF = (1.1575+ 1.6052)2 / { [ (1.1575)2 / (51) ] + [ (1.6052)2 / (51) ] }= 7.6325/(0.02627+0.05052)


t = [(µ1 – µ2) – d] / SE = [ (21.6157 -35.3004 ) – 0 ] / 1.66216 = -13.6847/1.66216 = -8.2330

For a two tailed test, the P-value would be the probability that a statistic of 99 degree of freedom exceeds -8.2330; greater or less than 8.2330 or -8.2330 respectively (Proctor, 1994).

From the t-distribution calculator at P (t < -8.2330) = 0.000, and P (t > 8.2330) = 0.000. Thus, the P-value = 0.000 + 0.000= 0.000

Therefore since the P-value (0.000) is much less than the set significance level of 0.10 then the null hypothesis in this case is rejected. The alternative hypothesis is true; the reaction time for the incongruent situation was higher than the reaction time for the congruent situation (Cramer, 1967).


The alternative hypothesis was that the reaction time for the incongruent situation was higher than the reaction time for the congruent situation. The results from these experiment supports this hypothesis, since the time that one would take to respond to a incongruent situation was much longer compared to a congruent situation. Therefore according to the element of this experiment, interference can divert the attention of a given individual from a given stimuli by impacting the neural or cognitive components of discriminatory attention (Korbmacher, 2016). This goes hand in hand according to Stroop (1935) and Sheibe, Shaver and Carrier (1967), it is an easier task to make an identification of a congruent word compared to the incongruent words.

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The interference of stroop effect on colours and words. (2019, Oct 10). Retrieved December 2, 2022 , from

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