Lecture 17 - Synaesthesia

Question 1

What is Synaesthesia?

Answer 1

• Atypical integration between and within the senses e.g motion and colour
• Blending of the senses: two diff responses in two diff parts of the brain e.g one sensory input yields a second sensory response = if you show a number of 6, she also sees the colour green OR if you play music, she hears it as well as seeing something.
• Like asking a typical person to think of a pumpkin

Question 2

What are aspects of synaesthesia? (ICECAP WIW)

Answer 2

• Within/across modalities: visual - letters and colours, or across - visual and hearing/taste with music
• Experience is real not hallucination - needs a trigger to have the experience
• Automatic: cannot be stopped
• Can feel normal to the synaesthete
• Passed on genetically: but more women
• Interaction between 2 things: inducer (mainly linguistic) and concurrent (mainly visual)
• Is one directional e.g numbers to colour but seeing a colour will then not induce a number as numbers are specific and colours are broad
• Within head (associator) or out there imposed on sensory world (projector)
• Can be advantageous as can help memory or creativity e.g musician

Question 3

What is a brief history of Synaesthesia? Is it more than learnt association?

Answer 3

• Early 1800s: based on the colour aspect and though it was Hyperchromaticity: additional new types of cones which elicits novel experience
• Late 1800s: Scientists picked up examples of types of syn = became cross-modal = not much research conducted
• 1900s: Interest declined - rise of behaviourism/learning theory = thought Syn was a learnt association

Question 4

What was a test looking at if Syn was more than learnt association? Baron-Cohen

Answer 4

• Came up with test to see if someone was a synthaesthete
• Ppt split into claimed syns and controls
• 117 word list was read to ppt, and asked for an association colour after each word = told it was a memory test and to learn it but syns were not told they were going to get retested
• Controls tested 1 week later and were told they could use any memory technique to remember the words
• Synaesthetes were tested a year later
• Consistency of colour-word associations was 37.6% in memory-matched controls, but syns had a 92.3% association
• But does not mean they see those things e.g think of green instead of see green = could mean they have a great memory

Question 5

What did Ramachandran do?

Answer 5

• Take standard image e.g square with circles making it up, then add colour or add spacing, people report vertical/horizontal lines
• Perceptual phenomena to do with grouping = changes the way we see an image e.g edges
  1) Set up simple grouping stimuli: chose numbers to make up a shape and non-syns group horizontally but those to Syn patients = numbers induce colours so they group vertically instead
  2) Shape hidden in these letters spaced everywhere, but syns turn into colours and can detect the shape easily
• Evidence of perceptual instead of association

Question 6

What did Dixon et al do to prove it is more than learnt association?

Answer 6

• Numbers for C elicit specific colours
• Pretesting included matching colours with numbers so it is established
• Classic Stroop experiment where you name colour of ink in in/congruent conditions
• Had congruent colour naming painted in actual syn experience, and incongruent where ink colours are swapped
• Patient C had a much larger reaction time in the incongruent condition, whereas controls only had a slightly longer RT

Question 7

What was another Stroop Test?

Answer 7

• Mirror-touch syn: can look at a real person or a video of person, and if that person is touched, they experience that touch
• Make ppts watch a video and poke you on either cheek and say if you experienced 1/2 pokes
• Can have a congruent: where you see it = where you are poked, or incongruent
• Found that incongruent had a much larger RT to make a decision but not for the controls as video does not interfere with touch
• The error rate is a lot higher in the mirror touch group in the incongruent condition

Question 8

Why do we have Syn?

Answer 8

• Inappropriate activation/connectivity between perceptual areas
• If you hear one input, another part of the brain is highlighted
  EXP:
• Image exp: have condition with words and imaging = list of words read, then word condition and tone condition
• Compared colour and black/white
• Controls show activity in colour change in colour system, and activity in words in word system
• In syns there is a lot of overlap: words trigger colour: say word and activity in colour system
• 3rd exp: Pushed controls by overtraining them to pair word-colour association AND still found no overlap happening
• Some specialised linkage in syns not in controls

Question 9

What did Ward say was the cause of Syn?

Answer 9

• When we are born, we are all Syns as we have massive inter-connectivity in neonatal brain
• Major task of brain during development is functional differentiation between areas via pruning (what links are not necessary)
• Syns may not complete this successfully = incomplete pruning = could be due to environment or the architecture of their brains