WebExp Demo Paradigm:   Stroop


The Stroop task, described by J.R. Stroop in 1935, gives insight into attention and interference in cognition. In its most familiar form the task consists of a sequence of coloured words. The task of the participant is to recognise the name of the colour in which each word is written. However, interference is introduced to this cognitive task by providing actual colour words as the stimuli. Thus for example the word RED will appear in green, and the subject is expected to respond with the answer "green".

Research in the late 19th century demonstrated that we are quicker to read aloud a word than to say aloud the word describing a patch of colour. Stroop put the two tasks together such that the quicker or perhaps more intuitive task interferes with the slower task. The original experiment provided a list of words simultaneously; we present the words separately in sequence.

The primary results from the Stroop experiment are:
  1. There is no interference from incongruent colours when reading the words aloud (compared to reading words in black)
  2. There is significant interference from incongruent words when naming colours (compared to naming colour patches)


  • Stroop, J. R. 1935. Studies of interference in serial verbal reactions. Journal of Experimental Psychology 18: 643-662.
  • MacLeod, Colin M. 1991. Half a Century of Research on the Stroop Effect: An Integrative Review. Psychological Bulletin 109: 163-203.

The Experiment

There is a practise section of 5 stimuli followed by an experimental section of 10 stimuli, including both words and colour patches.

Read the word and press the key which corresponds to the colour of the word -- NOT to the word itself! Your reaction time will be recorded based on your button press.

WebExp Demonstrations 2008 The University of Edinburgh