What practice changed

One unit holds the model's apricotty number. Three others hold the rest of its simplified tasting. One final unit holds the price guess.

Now the two ends need to be joined up. The taste units are on one side. The price guess is on the other. Between them run connections.

A connection is a link from one unit to another, and every connection has a strength.

Strength is a number saying how much one input affects the price. A strong positive connection pushes the price up more. A weak one barely changes it.

That is the one new thing in the picture beside this slide. Same four units as before, same wires, but now each wire carries a number.

Here is the rule that the rest of this model rests on.

Learning is allowed to change the connection strengths. Nothing else in this model can move.

This gives us one concrete possibility for how experience can leave a skill behind. The input arrives, the current strengths produce a guess, and feedback changes those strengths.

Real brains do change their connections with experience. They can also change which patterns become easy to notice, which connections remain, and how sensory information is organised.

Now, an honest word about all this.

Nobody has measured Vincenza's brain while she learns this task. A real has far more than four changing parts. This is a working model of one possible mechanism, not a photograph of her mind.

But the important part survives the simplification:

signals arrive, some strong and some weak.
each connection has a strength, deciding how much its signal counts.
error can guide changes to those strengths.

That narrower mechanism can be built out of numbers. Now we can watch exactly what it learns, without claiming that Vincenza's brain performs the same four-number calculation.

What practice changed

One unit holds the model's apricotty number. Three others hold the rest of its simplified tasting. One final unit holds the price guess.

Now the two ends need to be joined up. The taste units are on one side. The price guess is on the other. Between them run connections.

A connection is a link from one unit to another, and every connection has a strength.

Strength is a number saying how much one input affects the price. A strong positive connection pushes the price up more. A weak one barely changes it.

That is the one new thing in the picture beside this slide. Same four units as before, same wires, but now each wire carries a number.

Here is the rule that the rest of this model rests on.

Learning is allowed to change the connection strengths. Nothing else in this model can move.

This gives us one concrete possibility for how experience can leave a skill behind. The input arrives, the current strengths produce a guess, and feedback changes those strengths.

Real brains do change their connections with experience. They can also change which patterns become easy to notice, which connections remain, and how sensory information is organised.

Now, an honest word about all this.

Nobody has measured Vincenza's brain while she learns this task. A real has far more than four changing parts. This is a working model of one possible mechanism, not a photograph of her mind.

But the important part survives the simplification:

signals arrive, some strong and some weak.
each connection has a strength, deciding how much its signal counts.
error can guide changes to those strengths.

That narrower mechanism can be built out of numbers. Now we can watch exactly what it learns, without claiming that Vincenza's brain performs the same four-number calculation.