Feature Focus : The Stroop Test

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If you saw our recent post on the importance of Cognitive Testing, you’ll be familiar with how various tests are used in trials and research studies to monitor brain health and even act as diagnostic tools.

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Within the repertoire of cognitive tests which are widely used in research, we introduced the Stroop Test to you, an executive function test, suitable for assessing attention span, memory and even neurodegeneration. The Stroop Test was first developed by John Ridley Stroop in 1935 and has since evolved significantly taking on various forms. While there are a number of useful ways to measure the Stroop effect, the Trialflare Cognitive Testing Suite allows for two of the most popular methods of testing which are most widely reported in the scientific literature. We’ll introduce these two methods below.

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The Stroop Test - Basic Method

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The Stroop effect can be tested in a quick and easy experiment without any prior training or correction. While many forms of the test are popular, this simpler method involves presentation of written words of colours in one single phase. For example, “BLACK”, “RED” and “GREEN” might be presented in a variety of different colours (both congruent [matching, "GREEN" written in the colour green] and incongruent [mis-matching, "GREEN" written in the colour red]). In this way, the participant is exposed to an executive function challenge by potentially conflicting colour and word associations that they must overcome to make a correct guess.

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This ‘in at the deep end’ approach in a single phase without any prior training is a quick and easy method to gather useful data. While information from this method is very informative, there are some wider criticisms by the neuroscience and psychology disciplines who believe a true and validated test must be conducted using a more advanced method with normalisation and correction in place.

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The Stroop Test - Advanced Method

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The advanced Stroop method involves three successive testing phases which are required for carrying out some normalisation on each participants ability to identify words (i) without colour distraction, and (ii) colours without word distractions. The final phase which is the true Stroop Test using colour and word incongruence (mis-matching) to produce scores which are normalised against each participants ability to correctly identify colours and words alone without any additional executive function challenge in place. If that all seems quite complicated, here’s how it works in practice.

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Phase 1: Word Identification‍

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During this first phase of the experiment, the user is presented with words of colours in black font. For example, the words “BLACK”, “GREEN” and “BLUE” might be presented, all in black font, as to not distract the participant with any visual colour stimulation whatsoever. The idea of this phase is to gain some baseline data from the participant on how best they are able to identify what the word is on-screen.
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Phase 2: Colour Identification

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The second phase presents the same words, however, in the font colour of the word itself. For example, the word “GREEN” would be presented in a green font. This second phase ensures that the participant cannot be distracted by the word since it will always match the colour. In combination with the first phase, these data are crucial in normalising word and colour identification against the final test which challenges executive function through incongruence.
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Phase 3: Word and Colour Incongruence

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With the participant now having scores on their ability to (i) correctly identify the names words of colours, and (ii) correctly identify the colours these words represent we move onto the true test. By presenting the word of a colour in various different colours we are forcing the participant to activate executive functions and reconcile the associations between word and colour incongruence.

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Drawbacks of this advanced test are that it takes significantly longer, and after the two initial training phases, there is always a risk that the participant has lost interest or is performing differently due to altered interest or from distractions. Some participants might also be much quicker learners and perform better in the final phase after initial training than others. If this purpose of the test is not to measure ‘learning’ ability, this then becomes a confounding factor embedded into the scoring. For these reasons, it is acceptable for the Basic Method to be conducted as this removes any training bias.

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Why do we use the Stroop Test?‍

The Stroop Test is widely used due to its simplicity and ease-of-use. It’s relatively straight-forward setup and minimal training required (for both experimenter and participant) enables even lay persons to carry out research in this area. It is also simple enough to engage participants whatever their age or ability.

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The Trialflare Stroop Test‍

As part of the suite of cognitive tests Trialflare offers, the Stroop Test offers both simplicity in setup and the flexibility to undertake either test forms. Using a modern digital platform to assess the Stroop effect carries a large number of benefits when compared to the traditional paper and card methods which were first implemented in the 1930’s. The metadata which can be collected in our tests also enables the experiments to potentially collect hundreds of data points from each participant for deeper meta-analysis. These can include total and correct guess numbers and percentages, the average correct guess times and average guess latency after guesses. These can then be further sub-grouped to separate colour or word presentations.