C81MPR Practical Methods Lab 1

1. C81MPR Practical Methods (Lab 1) Dr. Danielle Ropar & Dr. Jonathan Stirk

2. Stroop (1935) Stroop (1935) Exp�t 1: had subjects read out loud the names of colour words printed on cards in different coloured inks. Each card had 100 colour-names on it. Words in the experimental list were all incongruent (e.g., RED written in YELLOW: RED) The control-condition cards were identical but all the colour-names were written in BLACK ink. The results showed no differences in time taken to read the word lists for the control and experimental groups So: when word name and word colour are incongruent, naming the word is not interfered with Naming the word is the REVERSE STROOP Many studies since have shown reverse task interference of colour of ink on word naming.Naming the word is the REVERSE STROOP Many studies since have shown reverse task interference of colour of ink on word naming.

3. However! Stroop (1935) Exp�t 2: had subjects read out loud the colour of the words printed on cards For the control condition he used coloured squares in the list This time the experimental group took longer than the controls So: When the colour of the ink and the word name are incongruent (don�t match), the word name interferes with naming the ink colour.

4. Stroop variant In a variation of Stroop�s experiment, we can present subjects with colour names in either the matching (congruent) or non-matching (incongruent) ink. Congruent (e.g., RED written in RED: RED) or Incongruent (RED) When subjects name the colour of the words they are slower on incongruent trials than on congruent ones This is known as the STROOP EFFECT

6. Try it yourself! Try naming the colour of the ink for the words below as quickly as you can:

7. And again�

8. Independent & dependent variables This design uses the experimental method (see stats lecture 2). In this experiment we have 1 IV which we are manipulating at 2 levels Congruency Congruent vs. Incongruent Our DV is what we actually measure and is normally the time taken to read lists or reaction time to make a response (in the exp�t you are about to do) Time is normally measured in seconds or milliseconds (thousandths of a second). We will use milliseconds (msecs) in today's experiment. This DV uses a RATIO scale of measurement.

9. Explaining the Stroop effect There are a number of theories used to explain the Stroop phenomena Two are: Relative Speed of Processing Parallel Processing There are others which we will not discuss today

10. Relative speed of processing In the incongruent condition, the two dimensions of the stimulus (colour and word) are involved in a 'horse race' competing to see which can get to elicit the response (response competition) The word name response often wins the race because it is assumed that reading a word is faster than naming a colour Then there is a competition for control of the response This takes time which accounts for the Stroop Effect

11. Speed of processing Both attributes arrive at different times to a decision making component which has limited capacity and can only process one input at a time (serially) PROBLEM: This theory cannot account for the Reverse Stroop effect (reversal of interference: colour of word ink interfering with word naming) �see next slide The speed of processing account argues that there is a competition or race between the two types of information and the information which is processed more quickly wins. In this case where information is incongruent ---it would mean reading words is a much faster process than naming colours. This would imply that if an individual were asked to read the word when the ink colour is different�there should not be an interference effect as reading words is processed more quickly. That is we should not get a REVERSE STROOP EFFECT!The speed of processing account argues that there is a competition or race between the two types of information and the information which is processed more quickly wins. In this case where information is incongruent ---it would mean reading words is a much faster process than naming colours. This would imply that if an individual were asked to read the word when the ink colour is different�there should not be an interference effect as reading words is processed more quickly. That is we should not get a REVERSE STROOP EFFECT!

12. Speed of processing account doesn�t predict reverse interference For the reverse task (word naming), in the incongruent pairing (e.g. red written in blue ink) the word identity (red) reaches the decision stage before ink identity (blue) even arrives. The response is made before ink identity is even processed. The same happens in the congruent pairing and so no time difference (interference) is predicted by this model for the Reverse StroopFor the reverse task (word naming), in the incongruent pairing (e.g. red written in blue ink) the word identity (red) reaches the decision stage before ink identity (blue) even arrives. The response is made before ink identity is even processed. The same happens in the congruent pairing and so no time difference (interference) is predicted by this model for the Reverse Stroop

13. Parallel processing The general idea is that potentially relevant evidence is collected until a decision is reached about which response to make. When there is a conflict between different sources of evidence it takes longer to reach a decision. The Parallel processing utilises the strength of the pathways that convey information that is important rather than the speed of processing. Pathways that have become automatic have greater strength and this leads to the asymmetry that produces the Stroop effect. This model appears to be able to handle all the empirical findings related to the Stroop effect. This account focuses on the STRENGTH of the information pathways rather than the speed of the processing. Because it focuses on strength --- this account predicts interference in both directions. That is, one will have difficulty reading the words due to an interference from the coloured ink information. This account focuses on the STRENGTH of the information pathways rather than the speed of the processing. Because it focuses on strength --- this account predicts interference in both directions. That is, one will have difficulty reading the words due to an interference from the coloured ink information.

14. Parallel processing

15. Separating the theories If we reverse the task (recognise word and �ignore� ink colour) what do the two theories predict? Speed account: There will be no reverse Stroop effect because word form would have been processed and decision made before ink was recognised Parallel systems: There will be a significant, but weaker, effect because the two signals are being processed (even though the ink signal is weaker). So we might expect to find some reverse interference

16. A journal article HALF A CENTURY OF RESEARCH ON THE STROOP EFFECT - AN INTEGRATIVE REVIEWMACLEOD CMPSYCHOLOGICAL BULLETIN 109: (2) 163-203 MAR 1991�� Abstract: The literature on interference in the Stroop Color-Word Task, covering over 50 years and some 400 studies, is organized and reviewed. In so doing, a set of 18 reliable empirical findings is isolated that must be captured by any successful theory of the Stroop effect. Existing theoretical positions are summarized and evaluated in view of this critical evidence and the 2 major candidate theories-relative speed of processing and automaticity of reading-are found to be wanting. It is concluded that recent theories placing the explanatory weight on parallel processing of the irrelevant and the relevant dimensions are likely to be more successful than are earlier theories attempting to locate a single bottleneck in attention.

17. Conducting a literature search

18. Basic steps Define the enquiry Gather Background Information Carry out the Search Locate the References Compile a reference list of cited material

19. Define the enquiry There are two basic questions that need to be answered What kind of information is needed? How much detail is required?

20. Gather background information Read textbooks relevant to the area Use subject dictionaries and encyclopaedias Look up any reference material that you have already been given Generate a list of keywords with which to search databases E.g. Stroop task

21. Carry out the search & locate references There are both printed and electronic databases of references Printed databases, e.g. Psychological Abstracts Electronic resources, e.g. PsycINFO, ISI Web of Science (WOS) Both require you to log on to your University account University of Nottingham Library

22. Compile a reference list Remember two points when referencing published material Give sufficient detail to enable anyone to identify the book or article to which you are referring Give the references in a consistent form Normally the APA format (see APA citation guide at Ohio State University) Use secondary citations for work that you haven�t read directly