Introduction


Last time:

Why are	people smarter than machines?

	- different hardware (or "wetware")

	lots of	slow, dumb, noisy components

	that cooperate to solve	problems:

		a massively parallel machine


What are the outstanding features of human computation?

	-constraint satisfaction

	-noise tolerance

	-interaction of	many types of knowledge


What are the features of connectionist models?

	-simple	processing units

	-connected via weighted	links

	-spread	activation and inhibition

	-relax to a solution
































	      More models: The skilled typist

People type fast!

	Interstroke interval is	shorter	than

	the time it takes for a	signal to go from

	hand to	brain and back.

How do they do it?

	Must be	a parallel, overlapping	process

Model:



















































	 More models: Interactive activation model


People are better at perceiving	letters	when they

are in words:

Paradigm:		Time

	*A=&		0

	####		70 ms later

	 A		later: forced choice
	 R

In a word:

	WAKE

	####

	 A
	 R

In a "pseudoword":

	MAVE






































	 More models: Interactive activation model


Model:






























































	 More models: Interactive activation model

Behavior:































































	 More models: Interactive activation model

This model demonstrated:


context	effects:

	top-down activation helps perception

Rule-like behavior:

	acts as	if it knows

	the orthographic rules of English

	(pseudoword effect)

Noise tolerance:

	cleans up noisy	inputs

	even for novel inputs!












































	     More models: The Jets & the Sharks

Motivation


Humans have a content-addressable memory

I'm thinking of	someone. They are:

	a former actor

	intelligent

	a former president

	old

You probably retrieved the right person,

even though part of the	description is incorrect!


Computers access memories differently:

To get an item out of memory, you need:

	an address (where it is	in memory)

	the CPU	gets the contents of that address

	puts it	in a working memory (register)



































	    More models: The Jets and the Sharks

The domain


Basically, the interactive activation model

applied	to memory

Suppose	we have	two gangs:
























































	    More models: The Jets and the Sharks

The Model































































	    More models: The Jets and the Sharks

Properties


1. Content addressable

   We can retrieve all of someone's name from their properties

2. Graceful degradation

   Works even with some	misleading information:

	"best match search"

3. Default assignment

   Missing features can	be "filled in"

4. Spontaneous generalization

   Even	though only specific properties

   of individuals are encoded

	prototype formation