1. To discuss this week What is a classifier? What is generalisation?
By an artificial algorithm, and by the brain
What are the basics of neural decoding?
Distributed vs. localised/modular representations
What is similarity space?
Neural similarity space
What is a neural representation?
What is a cognitive mechanism? How to find one?
Suppose you have a question about the brain. How can we find what is currently known about it?

2. Discussion: classifiers
What is an example of an artificial classifier that you interact with in everyday life?
What kinds of things is it good at?
What kinds of things make it fail?
Why do you think a classifier is needed for that problem?

3. A toy example of a classifier, using two feature dimensions
Weight
Height
Sumo wrestlers
Basketball
players
Classifier boundary

4. Some patterns are more separable than others, given a particular set of measurements
Weight
Height
Sumo wrestlers
Basketball
players
Faculty
Students

5. Neural decoding, as it is usually done
From: Norman, Polyn, Detre & Haxby (2006), Trends in CogSci, 10(9),

6. Generalisation, by classsifiers and by the brain

7. Generalisation, and its absence
Example: Shazam app
Recognise a recording
Try on a live version of the same song

8. Generalisation by the brain
Google Images search for “Jon Stewart”

9. Problems with pretty pictures
Caricature of a bad brain-imaging study:
Put people in a scanner, get them to do some task X
See which part of the brain lights up the most
Declare this is “the part of the brain responsible for X”

11. Modules What does it mean for something to be “modular” ?
Biological modules: organs in the body
Liver, kidneys, heart etc.
More distributed
Blood circulatory system, immune system
Is the brain modular?
Fodor (1983): “Modularity of Mind”
Functional modules vs. physically separated

12. Most brain areas have multiple functions
Most brain areas have multiple functions. Each mental function is supported by multiple areas
Saying
“Which is the part of the brain responsible for X?”
“Aha, it’s this bit!”
…is a bit like saying
“Where in the USA is the economy?”
“Aha, it’s in Wall Street”
Need to look at broad patterns of neural activation, distributed across multiple brain areas