Hancock et al. (2006)
From Psy3241
Monozygotic Twins' Colour-Number Association: A Case Study
Presentation By Mandy French
Contents |
Introduction
• Investigates the color-number associations of monozygotic twins age 12 at testing
• Origin of color-number association is known to be a colored number jigsaw puzzle
• At age 3 the association was first noted when a teacher asked the boys to report numbers, but they insisted on reporting color names
• The colors that were reported were synonymous with the colors shown on the “Early Learning Centre” number jigsaw puzzle that the boys regularly played with
• The brothers showed the same color to number pairings, but the association was not quit as strong for one of the brothers
• By age 12 the boys report what color a digit is as well as most letters
• Researcher was interested in determining if the boys show the Stroop-like interference effects that are commonly used and if they had enduring associations
Methods
• Name the color in which a digit is displayed
• Hypothesized that if the digit is colored according to the jigsaw puzzle, then the boys will be quicker when compared to incorrectly colored digits
Participants
• Monozygotic twin boys aged 12 years and 2 months
• Physically and intellectually similar
Materials
• The twins separately selected colors for each of the digits from 0-9
• Numbers were displayed in 200pt font about 6cm high on the screen
• The color selections the boys made were stored as congruent colors
• Incongruent versions were created by changing the colors of discordant pairs
• The swaps were all for adjacent numbers
Procedure
• Asked to name the color of the displayed digit as rapidly as possible
• Each digit was presented 8 times in one run of the experiment
• Each digit was presented 4 times congruent and 4 times incongruent per run
• Each boy ran the procedure 6 times over a couple of days
• A total of 24 trials were conducted for each digit
Results
• 49 of the 480 trials were removed for R and 51 were removed for T because the voice trigger failed to detect the word or was triggered by an extraneous noise
• 38 trials for R and 19 trials for T were removed because they were more than 2 standard deviations away from the mean
• Both boys had an increased reaction time to incongruent colors
• An Anova demonstrates an effect of congruence, but not a significant difference between the boys
• R made more color naming errors than T
• 11 errors for R and 1 error for T
• It is believed that T was more careful, which resulted in his lower error rate and slower reaction time
Discussion
• “Associator” Synaesthetes can see colors in the “mind’s eye”
• “Projector” Synaesthetes see the color as an overlay on the digit
• The boys experience is consistent with the finding that they do not report photisms or any sense of perceiving color, they just know that a particular number is a specific color
• Elias et al. showed the synaesthete showed much stronger activation in visual areas on several tasks than the learned associator
• It would be interesting to use fMRI to see in which group of synaesthetes the boys fit into
• The boy’s association is learned, but not practiced
• Both twins report the color-number association and do so with a very similar set of colors
• Even though both boys had not seen the jigsaw puzzle for at least 7 years at the time of testing, the accuracy of the match was remarkable
• It is estimated that the frequency of synaesthesia is 1 in 25,000
• Recent study demonstrates the possibility of the rate of synaesthesia being as high as 1 in 110
• Synaesthesia may not be an all or nothing effect, but may be more of a graded phenomenon with enduring associations at one end of the scale and full blown cross modal perception at the other
• R and T seem to fit at the mild end of the range
• R and T have reliable, long lasting associations that cause a Stroop interference, even though they do not report seeing anything
• A genetic effect for synaesthesia is possible because the boys’ mother also displayed a color-number association
Questions
Is it possible that if the twins practiced the learned association that the color-number association could grow stronger?
See also: Synesthesia
