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Same Shape - Different Colours: Both Meaning and Form Determine the Colours of Graphemes in Alphanumeric-Colour Synaesthesia. Mike J. Dixon, Kathleen Myles, Daniel Smilek, Patricia L. Duffy, Mark P. Zanna and Philip M. Merikle

University Of Waterloo

IntroductionIn alphanumeric-colour synaesthesia black digits or letters elicit conscious experiences of highly specific colours called photisms. For some synaesthetes photisms appear as projected coloured overlays that conform to the shape of the presented digit or letter...

Stimuluspresented

Description ofperception2 2

PD’s Digit Photisms PD’s Letter Photisms

ZB

T

University of Waterloo

B

Method

a) Impose a digit context by instructing P.D. to name the following DIGITS as quickly as possible…

1 3 5 8 4 7 3 Bb) Digit Stroop: name the video colour as quickly as possible.

B1 3 5 8 4 7 3 6

a) Impose a letter context by instructing P.D. to name the following LETTERS as quickly as possible… A E S Q R N H M B

b) Letter Stroop: name the video colour as quickly as possible.

BA E S Q R N H K

In Digit-Stroop trials list-wise context effects will bias P.D. tointerpret a as a digit. If so will elicit a brown photism that will speed colour naming. = congruent trial = fast RTs

In Letter-Stroop trials list-wise context effects will bias P.D. to interpret a as a letter. If so will elicit a green photism that will slow colour naming = incongruent trial = slow RTs

RESULTSColour Naming Response Times

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2/Z brown 2/Z green 3/B red 3/Bgreen /T green 7/T blue

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B B

For each coloured grapheme, what is a congruent trial in one context is INCONGRUENT in the other context.

Dig

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p<.03

p<.001

p<.001

p<.002

p<.007n.s.

Discussion

For 5/6 comparisons reaction times indicate that the same ambiguous graphemes generated different coloured photisms depending on whether they were interpreted as digits or letters.

Next we sought to provide a conceptual replication of these results. In Experiment 2 we tested a different synaesthete (J) using a paradigm designed to increase the saliency of the contextual manipulations.

Results

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BH

In the key conditions, ambiguous graphemes were presented in the context of achromatic digit strings or words (1 sec. duration). Flanking digits or letters disappeared, and ambiguous graphemes were coloured. J was to name the colour as quickly as possible.

Digit Context Letter Context

Day 1: Day 2:

Method

PredictionsIn the digit context flanking digits would bias J to interpret a as a digit. If so will elicit a gold photism that will speed colour naming. = congruent trial = fast RTs

In the letter context, flanking letters would bias J to interpret a as a digit. If so will elicit a purple photism that will slow colour naming. = incongruent trial = slow RTs

For each coloured grapheme, what is a congruent trial in one context is INCONGRUENT in the other context.

Colour Naming Response Times

0100200300400500600700800900

3/B re

d4/

H4/

H5/

S5/

S

7/T

gree

n

7/T

blue

ambiguous graphemes

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B H H

All congruency effects were significant - (all p values <.001)

EXPERIMENT 2Predictions:

Conclusions

Two experiments showed that the same ambiguous graphemes could elicit different coloured photisms depending on whether synaesthetes interpreted these graphemes as digits or letters. We conclude that the meaning of the presented grapheme that determines the colour of the photism in alphanumeric colour synaesthesia.

ResultsEXPERIMENT 1

B

Trials containing unambiguous digits or letters (e.g., 0123 or SIZE) were also intermixed with trials containing ambiguous graphemes. These trials were not analyzed.

0

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7

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Ambiguous Grapheme Photisms?

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7

J’s Digit Photisms J’s Letter PhotismsAmbiguous

Grapheme Photisms?

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2

Day 1:

Day 2:

Debate has arisen concerning whether photisms depend solely on the form of the presented grapheme, or whether the meaning of the grapheme also contributes to these synaesthetic colour experiences.

We sought to address whether the same ambiguous grapheme (e.g., ) could elicit different coloured photisms denending on whether it was interpreted as a digit or a letter. If the same form could elicit different coloured photisms depending on its interpretation, then we would have evidence that the meaning of graphemes plays a crucial role in determining the colour of these synaesthetic experiences.

Colour of ambiguous grapheme consistent with digit (D) or letter (L) interpretation

(D) (L) (D) (L) (D) (L)

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(D) (L)

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(D) (L) (D) (L)(L) (D) (L) (D)

CongruentIncongruent

University of Waterloo