Synaesthesia: an investigation using Stroop-like tasks and PET imaging Tyson Baker Psychology 347.3...

Synaesthesia: an investigation Synaesthesia: an investigation using Stroop-like tasks and PET using Stroop-like tasks and PET

imagingimaging

Tyson BakerTyson Baker

Psychology 347.3 Psychology 347.3 Monday, November 25Monday, November 25

Presented articlesPresented articles

Paulesu, E., Harrison, J., Baron-Cohen, S., Paulesu, E., Harrison, J., Baron-Cohen, S., Watson, J.D.G., Goldstein, L., Watson, J.D.G., Goldstein, L.,

Heather, Heather, J. et al. (1995). The physiology J. et al. (1995). The physiology of of coloured hearing: A PET study of coloured hearing: A PET study of colour-colour- word Synaesthesia. word Synaesthesia. Brain, Brain, 118, 118, 661-661- 676.676.

Odgaard, E.C., Flowers, J.H., & Brahman, Odgaard, E.C., Flowers, J.H., & Brahman, H. H. L. (1999). An investigation of the L. (1999). An investigation of the cognitive and perceptual dynamics of a cognitive and perceptual dynamics of a colour—digit synaesthete. colour—digit synaesthete. Perception, Perception, 28, 28, 651-664.651-664.

Paulesu et al. (1995)Paulesu et al. (1995)IntroductionIntroduction

Synaesthesia has been in scientific literature since John Locke Synaesthesia has been in scientific literature since John Locke (1690)(1690)– Over 300 years!Over 300 years!

Many Synaesthetes ridiculed as children, try to repress it, but Many Synaesthetes ridiculed as children, try to repress it, but it staysit stays– Remember having Synaesthesia all their lives; same inducer-Remember having Synaesthesia all their lives; same inducer-

concurrent connections earlier than 4 years oldconcurrent connections earlier than 4 years old Many musical composers theorized to have had ‘coloured Many musical composers theorized to have had ‘coloured

hearing’hearing’ Some (8) lexical-chromatic (sounds of words produces Some (8) lexical-chromatic (sounds of words produces

perception of colour) have colour mostly dependent on the perception of colour) have colour mostly dependent on the dominant letter of word (Baron-Cohen et al., 1993)dominant letter of word (Baron-Cohen et al., 1993)– 5 stated colour was not in visual field5 stated colour was not in visual field– 2 stated just above center of gaze2 stated just above center of gaze– 6 stated it took the form of the word6 stated it took the form of the word– 1 stated no particular shape1 stated no particular shape– E.P. had a specific shade for each word (Baron-Cohen et al., E.P. had a specific shade for each word (Baron-Cohen et al.,

1987)1987)

Paulesu et al. (1995)Paulesu et al. (1995)Introduction cont’d…Introduction cont’d…

Cytowic (1989) suggested hypothesis Cytowic (1989) suggested hypothesis that Synaesthesia was in limbic systemthat Synaesthesia was in limbic system– Xenon inhalation experiment did not test Xenon inhalation experiment did not test

limbic system hypothesis, but did show limbic system hypothesis, but did show widespread CBF decreases in the neocortexwidespread CBF decreases in the neocortex

Equipment failure?Equipment failure? Other information points to a cortical Other information points to a cortical

level (Sachs & Wasserman, 1987; level (Sachs & Wasserman, 1987; Sachs et al 1988)Sachs et al 1988)– Synaesthete was in a car accident and Synaesthete was in a car accident and

became colour-blind; Synaesthesia became colour-blind; Synaesthesia disappeared as well.disappeared as well.

Paulesu et al. (1995)Paulesu et al. (1995)HypothesesHypotheses

H1: Synaesthetes hearing words will show activation H1: Synaesthetes hearing words will show activation of brain areas responsible for colour perception under of brain areas responsible for colour perception under normal circumstancesnormal circumstances– E.g.. The fusiform gyrus (Lueck et al., 1989; Zeki et al., E.g.. The fusiform gyrus (Lueck et al., 1989; Zeki et al.,

1991)1991) H2: (Alternatively) Synaesthesia may be due to a H2: (Alternatively) Synaesthesia may be due to a

connection between the auditory verbal cortex and connection between the auditory verbal cortex and some associative visual area responsible for some associative visual area responsible for representing colours and letters conjointlyrepresenting colours and letters conjointly– Inferior temporal region used to identify objects based on Inferior temporal region used to identify objects based on

colour and shape (Corbetta et al., 1991)colour and shape (Corbetta et al., 1991) H3: Will the primary visual cortex (V1/V2) show H3: Will the primary visual cortex (V1/V2) show

activation?activation?– Yes: support for feedback connectionsYes: support for feedback connections– No: support that brain is capable of generating No: support that brain is capable of generating

perception of colour without V1 or V2perception of colour without V1 or V2

Paulesu et al. (1995)Paulesu et al. (1995)MethodsMethods

SubjectsSubjects– SynaesthetesSynaesthetes

6 females (5 R-handed, 1 L-handed)6 females (5 R-handed, 1 L-handed) Synaesthesia ONLY responded to wordsSynaesthesia ONLY responded to words Mean age was 45Mean age was 45 MRI scans checked for large anatomical damageMRI scans checked for large anatomical damage

– ControlsControls 6 females (5 R-handed, 1 L-handed)6 females (5 R-handed, 1 L-handed) No record of Synaesthesia, neurological or No record of Synaesthesia, neurological or

psychiatric disease, or currently on psychoactive psychiatric disease, or currently on psychoactive drugsdrugs

Mean age was 40Mean age was 40 Did not know the experiment was dealing with Did not know the experiment was dealing with

SynaesthesiaSynaesthesia

Paulesu et al. (1995)Paulesu et al. (1995)Methods cont’d…Methods cont’d…

Psychological assessmentPsychological assessment– National Adult Reading Test (Nelson, 1982)National Adult Reading Test (Nelson, 1982)

Test of general intelligenceTest of general intelligence

– Genuineness for Synaesthesia test (Baron-Genuineness for Synaesthesia test (Baron-Cohen et al., 1987)Cohen et al., 1987)

Describe colours of more than 100 lexical items, Describe colours of more than 100 lexical items, tested 1-10 months later without warning (mean tested 1-10 months later without warning (mean 6 months)6 months)

– Test of phonological-based Synaesthesia Test of phonological-based Synaesthesia or letter-based Synaesthesiaor letter-based Synaesthesia

PhotographPhotograph and and Fish->phonological basedFish->phonological based KickKick and and Knock->letter basedKnock->letter based


Psychological stimulationPsychological stimulation– 12 consecutive rCBF (radioactive Cerebral 12 consecutive rCBF (radioactive Cerebral

Blood Flow) measurements, 6 in each of:Blood Flow) measurements, 6 in each of:– Control taskControl task

Pure tones within human voice range for 0.5sPure tones within human voice range for 0.5s Instructed to tap left index finger for every tone Instructed to tap left index finger for every tone

heard, intervals were random between 0.5s-1.5sheard, intervals were random between 0.5s-1.5s

– Experimental taskExperimental task Similar as control task, but using single wordsSimilar as control task, but using single words All words highly imaginable concrete wordsAll words highly imaginable concrete words All subjects to listen passively, but still tap All subjects to listen passively, but still tap

fingerfinger


PET data acquisitionPET data acquisition– All subjects also received an MRI All subjects also received an MRI

scan coregistered with their PET scan coregistered with their PET scans to improve anatomical scans to improve anatomical localizationlocalization

– Used Used 1515O-labelled water (HO-labelled water (H221515O) O)

injected intravenously injected intravenously


MRI data acquisitionMRI data acquisition– Used to exclude anatomical lesions in Used to exclude anatomical lesions in

volunteersvolunteers– images aligned parallel to images aligned parallel to

intercommissural line and interpolated intercommissural line and interpolated to obtain a cubic voxel the size of 1 to obtain a cubic voxel the size of 1 mmmm

Permitted coregistration with PET scans; Permitted coregistration with PET scans; both MRI and PET voxels were converted both MRI and PET voxels were converted into cubes and combined into one imageinto cubes and combined into one image

Paulesu et al. (1995)Paulesu et al. (1995)ResultsResults

IQ estimates for Synaesthetes were in the superior IQ estimates for Synaesthetes were in the superior range (NART range 115-128)range (NART range 115-128)

Consistency scores were 90% and above for all Consistency scores were 90% and above for all 5 of 6 Synaesthetes reported numbers 1-9 had colour 5 of 6 Synaesthetes reported numbers 1-9 had colour

associations not consistent with the first letter of the associations not consistent with the first letter of the spelled numberspelled number

Synaesthetes experience colour during inner speech, Synaesthetes experience colour during inner speech, but not during reading—unless they subvocalize what but not during reading—unless they subvocalize what they are readingthey are reading

Colour percept was dependent on letter, not phoneme Colour percept was dependent on letter, not phoneme – E.g.. “Nice”->Chocolate brown, “Knock”->Biscuit, “Kind”-E.g.. “Nice”->Chocolate brown, “Knock”->Biscuit, “Kind”-

>Biscuit>Biscuit– 5 of 6 Synaesthetes’ colour percept was dependent on 5 of 6 Synaesthetes’ colour percept was dependent on

the first letter of the word, 1 of 6 percept was dependent the first letter of the word, 1 of 6 percept was dependent on the first vowelon the first vowel

Paulesu et al. (1995)Paulesu et al. (1995)Results cont’d…Results cont’d…

As expected, Both groups showed As expected, Both groups showed increased rCBF while hearing increased rCBF while hearing words compared to tones in areas words compared to tones in areas involving languageinvolving language– Bilateral superior and middle Bilateral superior and middle

temporal gyritemporal gyri– LH inferior frontal gyrusLH inferior frontal gyrus

Paulesu et al. (1995)Paulesu et al. (1995)Results cont’d…Results cont’d…

Synaesthetes also showed increased rCBF Synaesthetes also showed increased rCBF when hearing words compared to tones inwhen hearing words compared to tones in– RH middle frontal gyrusRH middle frontal gyrus– RH insulaRH insula– LH posterior inferior temporal (PIT) cortexLH posterior inferior temporal (PIT) cortex

Synaesthetes showed increased rCBF when Synaesthetes showed increased rCBF when hearing words compared to controls hearing hearing words compared to controls hearing words inwords in– RH middle and *inferior frontal gyrusRH middle and *inferior frontal gyrus– RH insulaRH insula– *RH superior temporal gyrus*RH superior temporal gyrus– LH posterior inferior temporal (PIT) cortexLH posterior inferior temporal (PIT) cortex– *LH superior occipital gyrus*LH superior occipital gyrus– *Bilateral superior parietal lobule junction*Bilateral superior parietal lobule junction

(top) Synaesthetes word vs. tone(top) Synaesthetes word vs. tone(bottom) Synaesthetes word vs. (bottom) Synaesthetes word vs. control wordcontrol word

Paulesu et al. (1995)Paulesu et al. (1995) Results cont’d…Results cont’d…

Synaesthetes showed significant Synaesthetes showed significant deactivations (word vs. tone)deactivations (word vs. tone)– *RH cingulate cortex*RH cingulate cortex– *Bilateral temporo-parietal junction*Bilateral temporo-parietal junction– LH insulaLH insula– LH Lingual gyrusLH Lingual gyrus– *LH Cerebellum*LH Cerebellum

Synaesthetes showed significant Synaesthetes showed significant deactivations (compared to controls)deactivations (compared to controls)– LH insulaLH insula– LH Lingual gyrusLH Lingual gyrus

(top) Deactivation in Synaesthetes (tone (top) Deactivation in Synaesthetes (tone vs. wordvs. word(bottom) Deactivation of Synaesthetes vs. (bottom) Deactivation of Synaesthetes vs. controls (tone only)controls (tone only)

Paulesu et al. (1995)Paulesu et al. (1995) Results cont’d…Results cont’d… No activation of primary visual No activation of primary visual

cortexcortex

Paulesu et al. (1995)Paulesu et al. (1995) DiscussionDiscussion Self-proclaimed first neurophysiological account of brain Self-proclaimed first neurophysiological account of brain

activity related to colour-word Synaesthesiaactivity related to colour-word Synaesthesia– Regarded as a “centrally synthesized percept rather than Regarded as a “centrally synthesized percept rather than

an a form of mental imagery”: perception, not imaginationan a form of mental imagery”: perception, not imagination Still to be explained why Synaesthesia is one-wayStill to be explained why Synaesthesia is one-way Any visual areas activated or inhibited by experiment Any visual areas activated or inhibited by experiment

cannot be due to real stimuli (blindfolds)cannot be due to real stimuli (blindfolds) Some numbers also have colours associated that are Some numbers also have colours associated that are

independent of the letters that make up the written form independent of the letters that make up the written form of that numberof that number– Support for a lexical componentSupport for a lexical component

Similar to normals when they associate the written form of a Similar to normals when they associate the written form of a word with the sound…(Stroop tasks?)word with the sound…(Stroop tasks?)

Strange; visual presentation of words automatically activates Strange; visual presentation of words automatically activates the visual orthographic lexicon (Patterson and Morton, 1985), the visual orthographic lexicon (Patterson and Morton, 1985), yet the Synaesthetes do not perceive colours while reading yet the Synaesthetes do not perceive colours while reading silentlysilently

Paulesu et al. (1995)Paulesu et al. (1995) Discussion cont’d…Discussion cont’d… The ambiguous location of colour perception The ambiguous location of colour perception

indicates that Synaesthesia is located in areas indicates that Synaesthesia is located in areas of visual processing with a much looser of visual processing with a much looser representation of the visual field than the representation of the visual field than the primary visual cortex or V4primary visual cortex or V4– Some suggestive evidence that some Synaesthetes Some suggestive evidence that some Synaesthetes

in current study showed use of V4 in their in current study showed use of V4 in their SynaesthesiaSynaesthesia

Cerebral colour-blindness linked to lingual-Cerebral colour-blindness linked to lingual-fusiform gyri lesionsfusiform gyri lesions– LH Lingual gyrus inhibited during SynaesthesiaLH Lingual gyrus inhibited during Synaesthesia– Suggestive of being necessary for colour perception, Suggestive of being necessary for colour perception,

with other areas (dorsal occipital, temporal and with other areas (dorsal occipital, temporal and parietal cortex) used in higher levels of visual parietal cortex) used in higher levels of visual processing involving colourprocessing involving colour

Paulesu et al. (1995)Paulesu et al. (1995) Discussion cont’d…(PIT Discussion cont’d…(PIT cortex)cortex) Evidence from this study, and previous studies Evidence from this study, and previous studies

(e.g.. Corbetta et al., 1991) suggest that the (e.g.. Corbetta et al., 1991) suggest that the posterior inferior temporal cortex is involved posterior inferior temporal cortex is involved in complex aspects of colour perception, in complex aspects of colour perception, particularly linking colour to shapeparticularly linking colour to shape– Area not shown to be activated in normals hearing Area not shown to be activated in normals hearing

words, but is used in semantic judgments based on words, but is used in semantic judgments based on matching preselected types of nouns and adjectivesmatching preselected types of nouns and adjectives

Explains much of “coloured hearing” if PIT Explains much of “coloured hearing” if PIT cortex is used in colour processing, visual and cortex is used in colour processing, visual and language feature integrationlanguage feature integration

Paulesu et al. (1995)Paulesu et al. (1995) Discussion cont’d…(RH Discussion cont’d…(RH frontal lobe)frontal lobe)

-Shown to be active in visual tasks of -Shown to be active in visual tasks of divided attention involving colour divided attention involving colour (i.e. looking for a red square in a (i.e. looking for a red square in a variety of other coloured shapes)variety of other coloured shapes)

-Due to divided attention between -Due to divided attention between words associated meaning and the words associated meaning and the colour perceived?colour perceived?

E.g. “grass” causes perception of blueE.g. “grass” causes perception of blue

Paulesu et al. (1995)Paulesu et al. (1995) Discussion cont’d…Discussion cont’d…(inhibition in LH lingual (inhibition in LH lingual gyrus and insula)gyrus and insula) Related to colour perception, converting Related to colour perception, converting

written letters to soundswritten letters to sounds Could be due to inhibitory feedback from Could be due to inhibitory feedback from

other active visual areas (PIT)?other active visual areas (PIT)?– Could be indicative of where audio-visual pathways Could be indicative of where audio-visual pathways

cross in Synaesthetes.cross in Synaesthetes. Related to readingRelated to reading

– Damage can cause inability to read while other Damage can cause inability to read while other language abilities stay intactlanguage abilities stay intact

Uncertain to relevanceUncertain to relevance– ‘‘shutting off’ due to attentional requirements?shutting off’ due to attentional requirements?

Not needed at the moment?Not needed at the moment? Subjects were blindfoldedSubjects were blindfolded

Paulesu et al. (1995)Paulesu et al. (1995) Discussion cont’d…Discussion cont’d… Can conclude that any increased Can conclude that any increased

activation of visual system is due activation of visual system is due to Synaesthesia because of to Synaesthesia because of blindfoldsblindfolds

Odgaard, Flowers & Bradman (1999)Odgaard, Flowers & Bradman (1999) IntroductionIntroduction

-Case study on 46y.o. female Psychology graduate regarded as “L”

-Naïve to her colour-digit synasthesia

-studied when she stated “two is yellow, of course”

-Experiment 1 to test if L’s synasthesia was discrete, memorable, durable, and involuntary but elicited

-Experiment 2 to test lexical processing of synasthesia

-Experiment 3 to investigate colour-digit patterns in Euclidian space

Experiment 1Experiment 1IntroductionIntroduction

Cytowic (1989) gave criteria for synasthesia, tested in Cytowic (1989) gave criteria for synasthesia, tested in this experiment by memory tests and various Stroop-this experiment by memory tests and various Stroop-like tasks.like tasks.– Theorized Synaesthesia to be in the limbic systemTheorized Synaesthesia to be in the limbic system

Neuronal modulation theory states Synaesthesia to be Neuronal modulation theory states Synaesthesia to be a result of crossed neural connections during brain a result of crossed neural connections during brain maturationmaturation

The memory tests are to remember colour-digit The memory tests are to remember colour-digit associations, which a synaesthete would obviously associations, which a synaesthete would obviously have an advantagehave an advantage

The Stroop-like tasks were used to measure the The Stroop-like tasks were used to measure the involuntary divisions in attention as a result of similar involuntary divisions in attention as a result of similar meaningfulness of the task distractermeaningfulness of the task distracter– Used to assure that the results on the memory tests are Used to assure that the results on the memory tests are

not just extremely superior memory or over learned non-not just extremely superior memory or over learned non-synasthesia colour-digit associationssynasthesia colour-digit associations

Experiment 1Experiment 1Methods: ParticipantsMethods: Participants

ControlsControls– 7 males, 4 females7 males, 4 females– 19 – 39 years old (mean = 27.6)19 – 39 years old (mean = 27.6)– Graduate or undergraduate students at University Graduate or undergraduate students at University

of Nebraskaof Nebraska LL

– 46 years old46 years old– FemaleFemale– Psychology Graduate Psychology Graduate

Relatively naïve to perceptual and cognitive factors Relatively naïve to perceptual and cognitive factors involved in Synaesthesiainvolved in Synaesthesia

– Raised in Choctaw and Anglo heritageRaised in Choctaw and Anglo heritage

Experiment 1Experiment 1Methods: StimuliMethods: Stimuli

Using a colour wheel, L gave a complete listing of 110 one-Using a colour wheel, L gave a complete listing of 110 one-digit and two-digit numbersdigit and two-digit numbers– Some unidentifiable on colour wheelSome unidentifiable on colour wheel

Experiment 3 will explainExperiment 3 will explain-identifiable digits on colour wheel were used for Stroop-type tasks-identifiable digits on colour wheel were used for Stroop-type tasks

5 types of Stroop-like tests5 types of Stroop-like tests– 8 lists each type (40 lists total)8 lists each type (40 lists total)– 13 items each list 13 items each list – Read aloud, stated when “Done”Read aloud, stated when “Done”– Baseline: Baseline: xxxxxxxx, , xxxxxxxx, , xxxxxxxx– Incongruent colour-word associates: Incongruent colour-word associates: SkySky, , GrassGrass– Incongruent colour names: Incongruent colour names: blueblue, , redred, , purplepurple, , greengreen– Synaesthetically incongruent coloured numbers:Synaesthetically incongruent coloured numbers:

L associates such that L associates such that 7272, , 99, , 88, , 77 then it would be presented in then it would be presented in colours such as colours such as 7272, , 99, , 88, , 77

– Synaesthestically incongruent coloured numbers with negative Synaesthestically incongruent coloured numbers with negative priming:priming:

L associates such that L associates such that 7272, , 99, , 88, , 77 then it would be presented in then it would be presented in colours such as colours such as 7272, , 99, , 88, , 77

Experiment 1Experiment 1Methods: Stimuli Methods: Stimuli cont’d…cont’d…

Memory testsMemory tests– 11stst: List of 20 single and double digit : List of 20 single and double digit

numbersnumbers– 22ndnd: List of same numbers as 1: List of same numbers as 1stst, but , but

in a new random orderin a new random order– 33rdrd: Complete list of 110 single and : Complete list of 110 single and

double digit numbersdouble digit numbers Given only to LGiven only to L

Experiment 1Experiment 1Methods: ProcedureMethods: Procedure

8 weeks prior to experiment 1, L gave 8 weeks prior to experiment 1, L gave complete list of 110 colour-digit associations complete list of 110 colour-digit associations and first 2 memory testsand first 2 memory tests– 11stst memory test, 10 minute discussion on the memory test, 10 minute discussion on the

characteristics of ligand-gated ion channels, 2characteristics of ligand-gated ion channels, 2ndnd memory test, 6 week interval, 3memory test, 6 week interval, 3rdrd memory test memory test

Controls were given the 1Controls were given the 1stst memory test, then memory test, then 1 random Stroop-like task from each of the 5 1 random Stroop-like task from each of the 5 types (approx. 10 min.), then 2types (approx. 10 min.), then 2ndnd memory test memory test

Controls given 1 practice trial on all 5 types of Controls given 1 practice trial on all 5 types of Stroop-like tasks, then 1 timed trialStroop-like tasks, then 1 timed trial

L given all 40 Stroop-like tasks over 2 sessionsL given all 40 Stroop-like tasks over 2 sessions

Experiment 1Experiment 1ResultsResults

L passed the durability and L passed the durability and memory requirementmemory requirement– 95% on 295% on 2ndnd test (10 min interval) test (10 min interval)– 93.6% on 393.6% on 3rdrd test (6 week interval) test (6 week interval)

Controls mean accuracy was Controls mean accuracy was 28.4% (SD=11.4%) on the 228.4% (SD=11.4%) on the 2ndnd test test (10 min interval)(10 min interval)

Experiment 1Experiment 1Results cont’d…Results cont’d… ControlsControls

– Baseline = Synaesthesthetically incongruent coloured numbers Baseline = Synaesthesthetically incongruent coloured numbers = Synaesthesthetically incongruent coloured numbers with = Synaesthesthetically incongruent coloured numbers with negative primingnegative priming

– Baseline < Incongruent colour-word associatesBaseline < Incongruent colour-word associates– Baseline < Incongruent colour namesBaseline < Incongruent colour names

LL– Overall slower than controlsOverall slower than controls– Baseline < Synaesthesthetically incongruent coloured numbers Baseline < Synaesthesthetically incongruent coloured numbers

< Synaesthesthetically incongruent coloured numbers with < Synaesthesthetically incongruent coloured numbers with negative priming < Incongruent colour namesnegative priming < Incongruent colour names

No differences between L and Controls on:No differences between L and Controls on:– BaselineBaseline– Incongruent colour-word associatesIncongruent colour-word associates– Incongruent colour namesIncongruent colour names

Controls were faster on:Controls were faster on:– Synaesthesthetically incongruent coloured numbers Synaesthesthetically incongruent coloured numbers – Synaesthesthetically incongruent coloured numbers with Synaesthesthetically incongruent coloured numbers with

negative primingnegative priming

Experiment 1Experiment 1Results rephrased…Results rephrased…

ControlsControls– xxxxxxxx, , xxxxxxxx, , xxxxxxxx = = 7272, , 99, , 88, , 77 = = 7272, , 99, , 88, , 77– xxxxxxxx, , xxxxxxxx, , xxxxxxxx < < SkySky, , GrassGrass– xxxxxxxx, , xxxxxxxx, , xxxxxxxx < < blueblue, , redred, , purplepurple, , greengreen

LL– Overall slower than controlsOverall slower than controls– xxxxxxxx, , xxxxxxxx, , xxxxxxxx < < 7272, , 99, , 88, , 77 < < 7272, , 99, , 88, , 7 7 < < blueblue, , redred, , purplepurple, ,

greengreen No differences between L and Controls on:No differences between L and Controls on:

– xxxxxxxx, , xxxxxxxx, , xxxxxxxx– SkySky, , GrassGrass– blueblue, , redred, , purplepurple, , greengreen

Controls were faster on:Controls were faster on:– 7272, , 99, , 88, , 77– 7272, , 99, , 88, , 77

Experiment 1Experiment 1DiscussionDiscussion

Functionally, L’s scores on the incongruent coloured Functionally, L’s scores on the incongruent coloured digits and incongruent coloured digits with negative digits and incongruent coloured digits with negative priming are similar to the scores on incongruent colour-priming are similar to the scores on incongruent colour-associate words and incongruent colour-words, associate words and incongruent colour-words, respectivelyrespectively– Indicative of lexical componentIndicative of lexical component

Cytowic’s (1989) theory of Synaesthesia processed in the Cytowic’s (1989) theory of Synaesthesia processed in the limbic system is discredited limbic system is discredited

Neuronal modulation theory should be altered to allow onset Neuronal modulation theory should be altered to allow onset of lexical abilityof lexical ability

L marginally faster at incongruent colour-word L marginally faster at incongruent colour-word (“Classic”) Stroop task(“Classic”) Stroop task– 1)As an experimenter, L was more attentive during testing1)As an experimenter, L was more attentive during testing– 2)Simply fast for her age (L = 46, controls mean = 27.6)2)Simply fast for her age (L = 46, controls mean = 27.6)– 3)L’s colour-digit Synaesthesia helps her ‘practice’ by 3)L’s colour-digit Synaesthesia helps her ‘practice’ by

being constantly exposed to coloured stimulus while being constantly exposed to coloured stimulus while processingprocessing

Experiment 2Experiment 2MethodMethod

ParticipantsParticipants– LL– ControlsControls

6 male, 4 female6 male, 4 female Mean age = 19.0 years, range 18-20Mean age = 19.0 years, range 18-20 Enrolled in Introductory Psychology Enrolled in Introductory Psychology

coursecourse– Partial course requirementsPartial course requirements

Experiment 2Experiment 2Method cont’d…Method cont’d…

StimuliStimuli– Stroop-like tasks (80 items each test, 8 types, 5 Stroop-like tasks (80 items each test, 8 types, 5

versions each type)versions each type) Instructed to draw line through items of target Instructed to draw line through items of target

colour(s)colour(s) Nonwords, numbers, colour-wordsNonwords, numbers, colour-words 1 or 3 target colours (24 targets per list)1 or 3 target colours (24 targets per list) Spectrally adjacent, spectrally non-adjacentSpectrally adjacent, spectrally non-adjacent xxxxxx, , xxxxxxxx, , xxxxxxxxxx, , 777777, , 99999999, , 8888888888, , 777777777777 , , blueblue, ,

redred, , purplepurple, , greengreen xxxxxx, , xxxxxxxx, , xxxxxxxxxx, , 777777, , 99999999, , 8888888888, , 777777777777 , , blueblue, ,

redred, , purplepurple, , greengreen 8 types: X1, N1, X3A, N3A, W3A, X3non, N3non, 8 types: X1, N1, X3A, N3A, W3A, X3non, N3non,

W3nonW3non

Experiment 2Experiment 2HypothesesHypotheses

H1: controls will score similar to past H1: controls will score similar to past research, specifically: 1 target colour research, specifically: 1 target colour < 3 target colours< 3 target colours Nonword < colour wordsNonword < colour words

– Spectrally adjacent < spectrally nonadjacentSpectrally adjacent < spectrally nonadjacent

H2: L will show classic StroopH2: L will show classic Stroop No specific hypothesis about her No specific hypothesis about her

incongruent number performanceincongruent number performance– Exploratory nature of experimentExploratory nature of experiment


ControlsControls– (X1 = N1) < (X3A = N3A) < (X3non = N3non)(X1 = N1) < (X3A = N3A) < (X3non = N3non)

single targets were faster than spectrally adjacent single targets were faster than spectrally adjacent nonwords, which were faster than spectrally nonwords, which were faster than spectrally nonadjacent nonwords, irrespective of stimuli being nonadjacent nonwords, irrespective of stimuli being X’s or #’sX’s or #’s

– (X3A, N3A) < W3A < W3non(X3A, N3A) < W3A < W3non– (X3non, N3non) < W3non(X3non, N3non) < W3non

Colour word lists took longer than nonword lists, Colour word lists took longer than nonword lists, with spectrally incongruent colour words taking with spectrally incongruent colour words taking longer than any other stimulilonger than any other stimuli

Experiment 2Experiment 2Results cont’d…Results cont’d…

LL– X1 = N1 X1 = N1 – X3A < W3A < W3nonX3A < W3A < W3non– X1 < X3A < X3non< N3A = N3nonX1 < X3A < X3non< N3A = N3non

Synaesthetically incongruent numbers Synaesthetically incongruent numbers are enough to produce delay regardless are enough to produce delay regardless of spectral adjacency of spectral adjacency


Between-group differencesBetween-group differences– L faster on X3AL faster on X3A


Controls performed as expectedControls performed as expected– Numbers produce no more Numbers produce no more

interference than X’sinterference than X’s– Single targets faster than 3 targetsSingle targets faster than 3 targets

Nonwords faster than incongruently Nonwords faster than incongruently coloured colour wordscoloured colour words

– Spectrally adjacent faster than spectrally Spectrally adjacent faster than spectrally nonadjacentnonadjacent

Experiment 2Experiment 2Discussion cont’d…Discussion cont’d…

L’s performanceL’s performance– PredictedPredicted

Matched control group on nonnumber Stroop listsMatched control group on nonnumber Stroop lists– UnforeseenUnforeseen

Tripling the number of target colours almost tripled Tripling the number of target colours almost tripled the time required (despite there still being 24 targets the time required (despite there still being 24 targets in the 80 item lists)in the 80 item lists)

– 10.30s to 28s(A), 30s(non)10.30s to 28s(A), 30s(non) 12.07s difference between X3A and N3A12.07s difference between X3A and N3A 9.3s difference between X3non and N3non9.3s difference between X3non and N3non Overall, spectrally adjacent and spectrally Overall, spectrally adjacent and spectrally

nonadjacent times are equalnonadjacent times are equal– Suggests due to memory overload from 3 target colours Suggests due to memory overload from 3 target colours

combined with the lexical component of her combined with the lexical component of her SynaesthesiaSynaesthesia

Experiment 2Experiment 2Discussion cont’d…Discussion cont’d…

Is the apparent irrelevance of spectrally Is the apparent irrelevance of spectrally adjacent target colours (N3A vs. N3non) due to adjacent target colours (N3A vs. N3non) due to simple overloading of attentional capacity (as simple overloading of attentional capacity (as Odgaard and colleagues suggest), or is it Odgaard and colleagues suggest), or is it somehow related specifically to an overload of somehow related specifically to an overload of attentional capacity combined with numbers, attentional capacity combined with numbers, possibly only removing or reducing the possibly only removing or reducing the advantage given by spectrally adjacent colour advantage given by spectrally adjacent colour targets to the other lists?targets to the other lists?– N3A vs.. N3non is N.S; avg(A) vs.. avg(non) is N.S., N3A vs.. N3non is N.S; avg(A) vs.. avg(non) is N.S.,

but…but…– X3A < X3non; W3A < W3nonX3A < X3non; W3A < W3non

Qualitatively, what kind of colour-digit Qualitatively, what kind of colour-digit associations does L experience?associations does L experience?– Experiment 3Experiment 3

Experiment 3Experiment 3IntroductionIntroduction

Because of the data obtained by L Because of the data obtained by L for Experiments 1 and 2, it seemed for Experiments 1 and 2, it seemed only logical to use the data of her only logical to use the data of her reports as an attempt to find out reports as an attempt to find out moremore– Basically making her classify colour-Basically making her classify colour-

digit associations that are impossible in digit associations that are impossible in Euclidian space, or group numbers she Euclidian space, or group numbers she might otherwise identify as dissimilarmight otherwise identify as dissimilar

Experiment 3Experiment 3Introduction cont’d…Introduction cont’d…

““Impossible in Impossible in Euclidean Euclidean space”?space”?

Experiment 3Experiment 3MethodMethod

StimuliStimuli– 20 single and double-digit numbers 20 single and double-digit numbers

printed on individual white cardsprinted on individual white cards 14 were numbers she could associate 14 were numbers she could associate

with the colour wheel with the colour wheel 6 were numbers she could not associate 6 were numbers she could not associate

with the colour wheel with the colour wheel – 57, 85, 86 (Red- greenish); 61, 64 (‘active’ 57, 85, 86 (Red- greenish); 61, 64 (‘active’

combinations of multiple colours); 98 combinations of multiple colours); 98 (orange-purple)(orange-purple)

Experiment 3Experiment 3Method cont’d…Method cont’d…

ProcedureProcedure– L was presented with same cards on 14 L was presented with same cards on 14

occasions separated by 24 hours or a occasions separated by 24 hours or a variety of distracter tasksvariety of distracter tasks

– L instructed to sort cards into 3-6 piles, L instructed to sort cards into 3-6 piles, each with at least 2 cards eacheach with at least 2 cards each

L would otherwise sort cards into at least 8 piles L would otherwise sort cards into at least 8 piles based on colour-digit associationsbased on colour-digit associations

– Resulting piles were recorded, entered into Resulting piles were recorded, entered into a dissimilarity matrixa dissimilarity matrix


Within-groups hierarchical cluster Within-groups hierarchical cluster analysis was performed on the analysis was performed on the dissimilarity matrixdissimilarity matrix– Four cluster solution had a Four cluster solution had a

coefficient of zero, so it was used (1-coefficient of zero, so it was used (1-3 ranged from 53.25 to 8.47 3 ranged from 53.25 to 8.47 respectively)respectively)


The four-cluster solution leads to a The four-cluster solution leads to a three-concept division for the non-three-concept division for the non-synaethesiasts synaethesiasts – ““reddish”, “not red, but typically reddish”, “not red, but typically

chromatic”, “other”chromatic”, “other” ““Reddish” are digits identifiable on the colour Reddish” are digits identifiable on the colour

wheel as having a red hue, sometimes with 57wheel as having a red hue, sometimes with 57 ““Not red, but typically chromatic” are mostly Not red, but typically chromatic” are mostly

digits identifiable on the colour wheel, but digits identifiable on the colour wheel, but sometimes containing 57, 61, 64sometimes containing 57, 61, 64

85 and 86 in “other” as being “green-red”85 and 86 in “other” as being “green-red” 98 was by itself as being “orange-purple”98 was by itself as being “orange-purple”


Suggest distinction between two ‘typical’ Suggest distinction between two ‘typical’ groupings could be due to a “…groupings could be due to a “…metaphorical/emotional dichotomy between metaphorical/emotional dichotomy between ‘warm’ and ‘cool’ colours.”‘warm’ and ‘cool’ colours.”– No further evidenceNo further evidence

Conclude that Euclidean space is insufficient Conclude that Euclidean space is insufficient means to explain the colour-digit means to explain the colour-digit associations with Synaesthesiaassociations with Synaesthesia– 98 was described as a “hollow sphere of orange 98 was described as a “hollow sphere of orange

and greyish purple that is as real as red or green” and greyish purple that is as real as red or green” but L stated she had “never seen anywhere in the but L stated she had “never seen anywhere in the world”world”

Odgaard et al. Odgaard et al. General DiscussionGeneral Discussion

Stroop-style tasks can be used to better fulfill the Stroop-style tasks can be used to better fulfill the diagnostic criteria of Synaesthesiadiagnostic criteria of Synaesthesia

Lexical component discredits idea that Synaesthesia Lexical component discredits idea that Synaesthesia occurs in the limbic systemoccurs in the limbic system– More likely due to the cortex being unable to modulate More likely due to the cortex being unable to modulate

sensory information; development after or during lexical sensory information; development after or during lexical developmentdevelopment

Synaesthesia could be the result of atypical neural Synaesthesia could be the result of atypical neural developmentdevelopment– Improbable due to onset of lexical abilityImprobable due to onset of lexical ability

Or, could be result of experiencesOr, could be result of experiences– Associations are learned, making child ‘prepared for Associations are learned, making child ‘prepared for

Synaesthesia,’ then Synaesthesia develops with lexical Synaesthesia,’ then Synaesthesia develops with lexical abilityability

Unclear how it works; no researchUnclear how it works; no research

Questions?Questions?

Synaesthesia: an investigation using Stroop-like tasks and PET imaging Tyson Baker Psychology 347.3...

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