The Stroop Effect

1
The Stroop Effect
2

• For the following words,
• say the ink color that
• the word is written in

3
RED
4
GREEN
5
RED
6
BLUE
7
GREEN
8
BLUE
9
GREEN
10

• How many of you had
• trouble saying the color that
• the word was written in?

11

• Did it take longer for you
• to name colors that were
• incongruent with the word?

12

• You have just experienced the Stroop Interference
  Effect

13
Which takes longer to say aloud?
Apple
or
14
J. M. Cattell (1886)

• Cattell reported that objects (and colors) take
  longer to name aloud than the corresponding words
  take to read aloud.

15
J. M. Cattell (1886)

• This is because, in the case of words and
  letters, the association between the idea and
  name has taken place so often that the process
  has become automatic, whereas in the case of
  colors and pictures we must by a voluntary effort
  choose the name (Cattell, 1886 p. 65)

16
Other support for differential practice
explanation

• Children younger than reading age, but who knew
  the words for the colors used, were faster on
  color naming than word reading

17
J. R. Stroop (1935)

• Interested in how best to explain interference.
• Was doing studies (similar to Cattells) looking
  at color naming versus word reading when he got
  the bright idea to combine the two attributes
  into a single stimulus.

18
Stroops Primary Questions

• What effect does the word have on trying to name
  the color and what effect does the color have on
  trying to say the word?
• What effect does practice have on the observed
  interference?

19
Stroops Experiment 1

• Examined the effect of incompatible ink colors on
  reading words aloud.
• 2 conditions in which read word
• Experimental words in each of 4 other colors
• Control words printed in black
• No differences between the 2 conditions in RT so
  no interference of color on reading words

20
Stroops Experiment 2

• Examined the effects of words when naming colors
• 2 conditions in which named color
• Experimental words in each of other 4 colors
• Control color blocks
• RT to name ink colors of incongruent words took
  longer than solid-color squares suggesting a
  significant interference effect.

21
Stroops Experiment 3

• Examined the effects of practice on the naming of
  ink colors of incompatible words over 8 days
• Interference from incompatible words appeared to
  decrease with practice.
• Additionally, all this practice resulted in a
  temporary interference of incompatible ink colors
  when reading words (reverse Stroop effect)

22
Stroops Conclusion

• A marked interference occurs when naming ink
  colors of incompatible color words.
• This interference may be the result of
  differences in the strengths of associations
  formed due to training levels in the two
  activities.

23
Current form of Stroop Task

• Two conditions
• Ink color and Word color are congruent RED
• Ink color and Word color are incongruent RED
• Two Tasks
• Name ink color
• Name word

24
Conceptual Encoding Theory

• Seymours (1977) theory states that a color word
  stimulus activates two conceptual codes in
  semantic memory.
• One corresponds to the color of the word (color
  memory), and
• the other to the color denoted by the word (word
  memory).

25
Conceptual Encoding Theory

• The time to access the word memory is shorter
  than the time to access the color memory and
  transfer that information into the word.
• Hence, when naming a word, there is no
  interference from the ink color because it is
  still processing.
• But when you name the ink color, the word has
  already been processed so you have to choose
  between two answers resulting in longer RTs.

26
Conceptual Coding Theory
dog green red cat keyboard
RED GREEN BLUE PURPLE PINK
GREEN
BLUE
PURPLE
RED
PINK
Word Memory
Color Memory
27
Conceptual Encoding Theory
Incoming Stimulus
Green

Word Memory
Color Memory
28
Conceptual Encoding Theory
Green

Word
Color
Word Memory
Color Memory
29
Conceptual Encoding Theory
Green
Green

Word Memory
Color Memory
30
Conceptual Encoding Theory
Green
Green

Word Memory
Color Memory
31
Conceptual Encoding Theory
Green

Green
Word Memory
Color Memory
32
Conceptual Encoding Theory
Green

Green
Word Memory
Color Memory
33
Conceptual Encoding Theory
Green

Green
Word Memory
Color Memory
34
Conceptual Encoding Theory

• Which stimuli will take you longer to name the
  color of the ink?
• RED BLOOD
• This theory hypothesizes that it is more
  difficult to say the ink color of a word when the
  word itself names a color.

35
In closing...

• Although the differential practice theory is
  commonly cited, to date there is no truly
  adequate explanation as to why the Stroop effect
  exists.
• The case remains a mystery...

36
but the truth is out there.
37
End