IA stroop effect

Participants

Opportunity sampling was used to select three participants in each of four age groups (11- and 12-year-olds in Year 7; 16- and 17-year-olds in Year 12). Four participants were male and eight female. To avoid researcher bias, the participants were allocated random numbers and tested individually.

Materials

The materials consisted of a consent form for participants (Appendix i (a)); permission letter for teachers (Appendix i (b)); standardised instructions/briefing and de-briefing note (Appendix ii); a raw data collection sheet (Appendix iii); a Stroop word list (Appendix iv); a stopwatch; and numbers (for random participant selection).

Procedure

The experiment took place in a quiet, well-lit classroom. Before beginning, the researcher read the briefing note aloud (Appendix ii) to the group. The participants selected numbers randomly.

The participants were called using the numbers; and their age, gender and nationality recorded. The participants were then tested in two ways: (1) reading the words; (2) naming the colours of the words. The instruction was given, in both instances, to read/name the words/colours from left to right starting at the first row; as quickly as possible. The time taken for each test was recorded. The procedure was conducted twice for each participant.

Lastly, the participants were questioned about their performance and reaction to the experiment. The researcher noted the answers on the raw data collection sheet (Appendix iii), along with incidents where participants encountered difficulties. The participants were consequently debriefed  (Appendix ii) and the experiment concluded.

RESULTS

Description

The scores were compiled (Appendix v), then analysed using the statistical measures of mean, range and standard deviation (Appendix vi). The combined trials (Trials One and Two) were considered using the total sample and by age group.  

The mean time to name the colours of the words was 13.17 seconds longer than the time to read the words (Figure 1). The range in time to name the colours was 14.70 seconds; and the range in time to read the words was 12.02 seconds.

The reaction time of the participants varied by age (Table 1). The interference was least on the 12-year-olds, where the difference in mean time between reading the words and naming the colours was 11.22 seconds.  The age group most affected was the 17-year-olds, where the difference was 16.91 seconds (Figure 2).  

Figure 1: Mean overall reaction times for reading words and naming colours

 

Table 1: Mean reaction times for reading words and naming colours

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Figure 2: Mean overall reaction times for reading words and colours, by age of participants

The time range to read the words was greatest in the 12-year-olds (10.43), whereas that to name the colours was greatest in the 17-year-olds (13.68) (Table 2).  

Table 2: Range, by age, for reading words and naming colours

Analysis

The mean was calculated for both the total sample group and by age band. The longer times taken to name the colours indicate a significant level of interference.

The results show an inverse correlation. The 12-year-olds had the highest mean time to read the words (15.04 seconds) and the highest spread of results (range: 10.43), suggesting divergent ability to read within this age band. The 17-year-olds had the lowest mean time to read the words (10.30 seconds), but the highest spread of results when naming the colours (range: 13.68). These differences may have contributed to the apparent lesser and greater Stroop Effects in these two age bands. 

The participants’ gender and nationality was irrelevant. The trials were parametric as the participants were selected randomly to eliminate researcher bias; and no freedom was allowed other than post-trial interviews – although using set questions still ensured researcher control.

DISCUSSION

The results confirmed that it is instinctive to read words correctly regardless of their colour; but more difficult to name the colour when incongruent colour word-pairs are presented.

Whereas the mean time for reading words was expected to decline with increased age of the participants, reflecting greater experience in reading, the results for the 12-year-old participants did not follow this trend. Similarly, the mean time for naming the colours did not show a distinct age-related trend.

The experiment could have been improved had more participants been taken from fewer age bands in the sample population. A small sample unrepresentative of the greater population is a weakness of opportunity sampling, Hill (1998). With larger numbers, differences in the cognitive and behavioural development by age band might be detected. Alternatively, all the participants could have been the same age.

By design, the experiment was straightforward, with little room for human error. All controls possible were implemented, thus minimising the effect of any Extraneous Variables on the Dependent Variable. However, in laboratory experimentation, control over all the variables is impossible; and the artificial conditions may produce unnatural behaviour that lacks ecological validity, Hill (1998).

The research methodology was simple as each participant repeated the two reading trials twice. The nationality of the individual participants did not lead to any bias, as it was not considered.

The trials were conducted in English. The potential confounding variables such as foreign language speakers, learning difficulties, or physiological anomalies, cannot be discounted.

Future studies of the Stroop Effect could focus on language, to evaluate the influence of this on the participants’ reaction times. The test could also be conducted in the students’ respective mother tongues and compared to their performances in English, to ascertain the influence of language level.

The extent of the Stroop Effect is questionable. Stroop interference is a measure of two cognitive problems: overcoming integration and managing two conflicting information sources. The integration problem can be overcome with practice, with the extent of interference reducing with successive trials such that integration of the two dimensions (word and colour) and non-integration of the two dimensions gives similar results, MacLeod (1998). This is not taken into account during simple measures of the Stroop Effect, as in this experiment.

The design of the experiment was sound. The researcher was competent to conduct the experiment and behaved professionally throughout the procedure. All forms of ethical procedure were observed.

CONCLUSION

This experiment confirmed that interfering stimuli affect cognitive processes. A significant difference was found between the ability to read words and name colours (in incongruent colour-word pairs): overall, naming took 13.17 seconds longer than reading, the time to name being twice as long as to read.

Measurable differences were also noted between the different age bands of the participants, with 12-year-olds taking only 1.7 times as long to name colours compared to 17-year-olds who took 2.6 times as long. This phenomenon has not been explored in this experiment, but is worthy of further research.

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REFERENCES

BOOKS

• Engel-Andreasen, M. (2008). The Effect of Interfering Word Stimuli upon Naming Colours Serially. Nyborg Gymnasium.
• Glassman, W. E. and Haddad, M. (2004). Approaches to Psychology. Fourth Edition. McGraw-Hill House, England.
• Hill, G. (1998). Oxford Revision Guides, AS & A Level Psychology. Oxford University Press, New York.

WEBSITES

• Cognitive interference. http://faculty.washington.edu/chudler/words.html. Last updated: 15 February 2010. Viewed 19 February 2010
• Colin MacLeod. http://www.psychology.uwaterloo.ca/people/faculty/cmacleod/index.html. Last updated: 4 January 2010. Viewed 3 February 2010.
• J Ridley Stroop. http://wikidoc.org/index.php/Stroop_effect. Last updated: 13 April 2008. Viewed 17 February 2010.

• Stroop Effect. http://psychclassics.yorku.ca/Stroop/. Last updated: unknown. Viewed 19 February 2010

ARTICLES

• Atwood, J. Psychology Internal Assessment: The holy guide to writing your report. School handout.
• Bower, B. (1992). . Science News. Volume 141, pages 312 -316.

Found at http://www.thefreelibrary.com/Brother+Stroop's+enduring+effect-a012249057. Last updated: unknown. Viewed 19 February 2010.

• MacLeod, C. (1998).  Training on integrated versus separated Stroop tasks: The progression of interference and facilitation. Memory & Cognition Volume 26(2), pages 201-211.  

Found at http://arts.waterloo.ca/-cmacleod/Research/Publications2.htm. Last updated: 4 January 2010. Viewed 3 February 2010.

DICTIONARIES

• New Oxford American Dictionary. Macintosh OS X.
• Oxford American Writer’s Thesaurus. Macintosh OS X.

APPENDICES

Appendix i (a)         –         Informed consent form  

Appendix i (b)         –         Permission letter

Appendix ii         –         Standardised instructions/Briefing and De-Briefing note

Appendix iii         –         Raw data collection sheet

Appendix iv         –         Stroop word list

Appendix v         –         Composite raw data

Appendix vi         –         Composite data, analysed statistically

Appendix vii         –         Statistical calculation formulae

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Appendix i (a)

INFORMED CONSENT FORM

4 February 2010

Dear Parents

RE: PERMISSION REQUEST TO PARTICIPATE IN A PSYCHOLOGY EXPERIMENT

As a standard level psychology student, I am required, as part of the Internal Assessment process, to perform a simple experiment and analyse the data collected. I plan to conduct a Stroop Test and would like to use Mrs Carter’s Year 12 psychology class as a sample group for the test.

In the Stroop Test, students are given a list of words to read. Each word is printed in a different colour. There are two time intervals taken, one for purely reading the list and the second variable is reading the colours instead of the words. The independent variable of time is measured in both instances. There is no cultural or ethical bias in performing the test.

The results of the test will give a statistical measurement of cognitive reaction time to both sets of variables. Your child will remain anonymous throughout this experiment and it will be held in controlled conditions. Only the data will be studied. Students will receive a full debriefing at the end of the experiment.

I, therefore, kindly request your permission for your child to participate in this simple experiment on Wednesday, 10 February 2010 (during your child’s psychology lesson).  

Yours sincerely

Olivia Scott

Year 13 C

SL Psychology student

I _____________________________________ give/do not give (circle desired response) permission for my child __________________________________ to take part in the experiment.

Signature ___________________________                 Date ________________________

Please complete and return by Sunday, 7 February 2010.

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Appendix i (b)

PERMISSION LETTER  - YEAR 7

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Appendix i (b)

PERMISSION LETTER  - YEAR 12

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Appendix ii

STANDARDISED INSTRUCTIONS/BRIEFING AND DE-BRIEFING NOTE INSTRUCTIONS

• This psychology experiment will run the course of this lesson.
• To ensure that a controlled environment/lab conditions is maintained, it is very important that you cooperate and follow instructions.
• Do not disturb the experiment while it is taking place (if you are not participating in the experiment itself).
• Do not interact with each other or with me (other than being briefed and debriefed and taking part in the experiment).

• Those who are have participated, please sit (in allocated area) and continue with your school assignments. It is very important that you remain silent and do not interfere with those participating at any stage.
• Those who are participating, please take a number. This is done to ensure there is no researcher bias. Do not share your number. When your number is called, you will participate in the experiment and then return to your seat, where you will continue with your school assignments, remaining silent and not interfering/disturbing anyone else, including those participating in the experiment.
• You will now be briefed before the experiment, and once all the participants have completed the experiment, you will be debriefed. The experiment will then be concluded.

BRIEFING

• You are about to participate in a psychology experiment. Your reaction time in reading printed words and then reading the colour of the printed words will be measured.
• You have the right to withdraw from this experiment at any stage.
• Your name, age, nationality and identity will remain confidential.
• At the end of the experiment you will be fully debriefed.
• During the test, you will be asked to read a list of words. You are to read the words as quickly as you can. The time taken for you to read these words will be recorded.
• You will then be asked to name the colours the words are printed in. You are to name the colours as quickly as you can. The time for you to name the colour of the word will also be recorded.
• Both tests will be repeated twice.
• If you make a mistake (clarify what meant by ‘mistake’ – wrong test done), you will be asked to start that test again from the beginning.
• If you have any questions, please address them now.

DEBRIEFING

• The aim of this experiment was to test your reaction time to read a list of words as you see them and then to test your reaction time when asked to name the colours the words were printed in. More specifically, the interference of the colour stimuli in your overall reaction time between the first and second test was measured.
• Your results are highly beneficial to this experiment and I value and appreciate your participation.
• Should you have any further questions, please do not hesitate to ask me (Olivia Scott, Year 13 C).

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Appendix iii

RAW DATA COLLECTION SHEET

Date        

Participant details:

Age        Gender                        Nationality        

Mother tongue                Glasses/Lenses                

Analysis of data:

Additional observations:

Which words tended to be difficult?        

Was this the same word?        

Did the colour of the word make a difference?        

Did the test become easier or harder the second time?        

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Appendix iv

STROOP WORD LIST

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Appendix v

COMPOSITE RAW DATA

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Appendix vi

COMPOSITE DATA, ANALYSED STATISTICALLY

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Appendix vii

STATISTICAL CALCULATION FORMULAE

Mean

Value x frequency

Sum of frequency

Range

Differences between maximum value and minimum value

Standard Deviation

Calculated using Microsoft Excel functions

Proportional Increase

        Mean time to name colours

        Mean time to read words

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