Week 10 Synaesthesia & idiosyncratic perception

Question 1

What is synaesthesia

Answer 1

• Gr. ‘together/with’ + ‘feeling/percieving’
• When one sensory stimulus evokes two specific consistent, concurrent perceptual
  experiences
  o One percept plus another – they are paired and are consistent throughout life, and are concurrent, occurring at the same time
  o Grapheme-colour
  o Taste-shapes
  o Word-taste
  o Personification
  o Colour-sound

Question 2

Synaesthetes

Answer 2

o People who experience synaesthesia
o 0.1-4% of population
o Women > men but range 1:1 to 6:1
 Variable ranges – fear of reporting, women more likely to self-report
 Maybe don’t realise they are synaesthetes – it is the way the world has always been
o Runs in families
o Seems to be congenital
 Vs adventitious syn – meditation, deafferentation drugs
 Not true syn
 Deafferentation – damaged pathway, that area of cortex lacks
info, another area invades, get linking of senses

Question 3

History

Answer 3

• First reported by Francis Galton
  o The visions of sane persons
   People who have perceptual experiences that aren’t insane
  o Notes familial component
• Long considered an unreliable, unscientific phenomenon
  o Scientific fad like phrenology

Question 4

Resurgent interest in the 2000s

Answer 4

o Partly due to neuroscience: explosion of neuroscience and advancement in
techniques
o Partly due to psychology: behavioural consequences of synaesthesia, correlations with intellect and creativity
 Essay by Locke on colour-sound syn
 Essay by Fechner
o Partly due to publicity/awareness: synaesthetes sharing their experience and others trying to create synesthetic experiences
 Luria
 Mind of a mnemonist – could remember everything
 Memories were projected
 Cytowic
 Neighbour who was cooking described his food as shapes
 Trying to create experience
 Son et lumiere
 Organ that created different colours of light as you played
 At concerts with lights

Question 5

Types of synaesthesia

Answer 5

• 50-60 types currently described
• Some examples
  o Inducer-concurrent
  o Grapheme – colour
  o Tone – colour
  o Taste – touch
  o Lexical – gustatory
  o Visual motion – sound
• Rarely bi-directional but can be

Question 6

Synesthetic pairings

Answer 6

• Pairings are highly individualised and consistent throughout life
• May be
  o Completely arbitrary
   7 = light blue with a nice, calm personality
   No logic to it
  o Semantically influenced
   14 fourteen elicits green
   Barbara elicits rhubarb
   Phonetic pairing
  o Heightened levels of common cross-modal associations
   Y elicits yellow
   Low pitch sounds elicit darker colour
   Commonalities across population
• Pairings are concurrent – both percepts are experienced and can overlay
  o E.g. if 7 usually elicits blue and I write 7 in yellow – see yellow over the blue

Question 7

How do pairings develop

via experience

Answer 7

 Early childhood experiences
 Pairings early on in visual world as visual acuity develops
 Letters on wall – see the shapes and colours associated
o Later on develop semantic concept on what a letter is and that colour pairs with the concept
 Maybe every time there is an A# there is purple coming across on the baby mobile
o Over time the tones and colours become linked
 Fridge magnets
 Salient experiences
 Conditioned associations
 Pre memorial learning
 Learning before you know what learning is
 The brain’s way of making sense of the world before you have
semantic knowledge

Question 8

How do pairings develop

innate

Answer 8

 Highly individualised
 Always been there in their life
 Sometimes people say those pairings present in the enviro are wrong
 Those colours don’t match their synaesthesia
 How could they have learned it if it doesn’t occur in the enviro
 Hereditary component
 Non synaesthetes
 Have innate tendencies
 Certain sounds have shapes
 Certain tones match certain colours better

Question 9

How do pairings develop

subjective idealism

Answer 9

 Are these pairings illusory?
 Overactive imaginations?
 Fake?
 Simply subjective?

Question 10

Bouba-kiki effect – innate?

Answer 10

• Kohler’s experiments in the 20s/30a ‘takete-baluba’
  o Roundness and sharpness of shape match phrasing
• Sapir’s 1929 paper on ‘mal-mil’ tables
  o Big table mal, small table mil
  o Phonetic? – mal is longer
  o Proprioceptive? – mal open mouth big
  o Words in language?
   Big things – large, giant – big mouth
   Small things – tiny, teeny – small mouth pattern
• Ramachandran and Hubbard’s experiments in 00s ‘kiki-bouba’
  o Sharp one is kiki
  o Round one is bouba
  o There is sound – shape linkage in the brain even in non synaesthetes

Question 11

Bouba-kiki effect

These experiments suggest:

Answer 11

o Certain sounds have a shape to them
o Bouba-kiki suggests there is a sound-shape correspondence in the brain
 Is there also a synesthetic pre-disposition ?
o Continuants
 (/m/ /s/) tend to be curvy
o Plosives
 (/k/ /t/) tend to be sharp
o Sound symbolism
 Certain sounds have meaning, are embolic
 Take away plosive phonemes, makes it less cutting
 Addict vs dependent – takes away stigma
- It seems certain sounds:
o Have shape to them
o Or a colour (O’s are white, X’s are black)
o Or a function (‘sn; links to nose, ‘fl’ to movement)
o Or a taste (‘ouu’ sweet, ‘ah’ sour)
o Innate cross-modal (syn) tendencies… the foundation of language?
 Maybe this is how humans started talking – brain has innate tendencies to make a sound descriptive of what we see in the environment

Question 12

Subjective idealism?

Test and re-test repeatedly

Answer 12

 Adds objective proof
 Shortcomings – need longitudinal study
 Need participants that are willing to be tested over decades

Question 13

Subjective idealism?

Test perceptual groups

Answer 13

 Testing not over time but in one moment
 Is your pairing altering what you can process sensory wise and does it show up in your detection ability
 Colour helps group things together – see colour of berries, it groups them separate from the rest of the tree
 If having specific colours for graphemes, you should be able to group those letters easily based on colour
 If letters and number have set colours
 Grouping would happen easily (similarity grouping)
 Process things differently because see them instantly as being different from the rest

Question 14

Subjective idealism?

Test stimulus detection

Answer 14

 Design test stimuli to see if things are detected quicker
 Pop out effect
 Non syn see a bunch of noise, synaesthetes see a number pop out quite quickly
 Colour should aid detection

Question 15

Subjective idealism?

Test Stroop timing

Answer 15

 Usual Stroop test challenges executive function – your ability to process conflicting information
 When word doesn’t match colour font
 Takes more time for process info
 Targets that individuals’ concurrent percepts
 RTs decreased because they see their syn pairing colour on top of the number shown
 Takes shorter time to process

Question 16

Cortical processing

Answer 16

• In the brain, what causes these mixed sensations
• Presumably need concurrent activation in 2 sensory cortices – some sort of cross-
  activation

Question 17

Is this cross activation direct or indirect?

cortical processing

Answer 17

o Adjacency of sensory cortices commonly involved suggests direct
 Linking regions near in the brain
o Unidirectional ‘driving’ also suggests direct
 One inducer always induces the same concurrent – direct specificity
 Feed-forward connections, topographic arrangement
o If activating at subcortical level, mixing signals before the brain – indirect
 If indirect could be at a level of the brainstem or thalamus
 Activating two pathways due to crossing of info

Question 18

Is this cross activation due to disinhibited connections or extra connections?
Disinhibition

Answer 18

 Connections that are usually inhibited
 Suggests that all of us potentially have cross wiring in the brain – and under the right there can be disinhibition
 But this is not true synaesthesia
 For
 Adventitious synaesthesia
 Under drugs, deep meditation, sensory deafferentation
 Against
 Adventitious is not highly individualised
 Is not consistent
 Not topographically organised
 Not true synaesthesia – is transient

Question 19

Is this cross activation due to disinhibited connections or extra connections
Extra connections

Answer 19

 One area directly linking to another – supplementary connections
 For
 MRI, DTI studies
o Suggest increased connectivity in a network model
 Structural and functional neuroimaging
o More cells there than a normal brain – more neurons o More white matter tracts connecting region in a synesthetic brain
o Syn brain actually has larger cortical mass and more
connections in some areas
 E.g. Grapheme-colour synaesthetes have increase cortical volume in V4 and V8, and have increased structural
connectivity between the areas
 Against
 Not really one that exists

Question 20

Is this cross activation due to disinhibited connections or extra connections
Is it both disinhibition and extra connections?

Answer 20

 Disinhibition early on in life
 This strengthens synapses and promotes growth – leading to moreconnections
 Interact, work together to give brain extra connections between
regions, leading to synaesthesia

Question 21

Life with synaesthesia

Answer 21

• Disadvantages
  o Ridicule, criticism
  o Personal bias – might affect preferences on food, odours, words
  o Visual obstruction
• Advantages
  o Seen as advantage with creativity
  o Helps recalling, manipulating – benefits on memory
• Could it enhance intellect and creativity?
  o Seen in creative people and highly intelligent people
  o Help inspire creativity
  o Aid in ability to recognise equation, have colour coding etc.

Question 22

Week 10 Synaesthesia & idiosyncratic perception