Date post: | 18-Jan-2016 |
Category: |
Documents |
Upload: | lucas-ward |
View: | 213 times |
Download: | 0 times |
COGS001Fall 2002
Module 6: Memory & Knowledge RepresentationLecture 2
An addition game
1 2 3 4 5 6 7 8 9
Two players, alternating turns
Nine cards, numbered from 1 to 9, are face up on the table
On each turn, pick one of the remaining cards
The winner: First player to hold cards adding up to 15
Another game
X 6 7 2
1 5 9
8 3 4
Two players, alternating turns
Board divided into 3 x 3 squares
On each turn, choose an unmarked square& mark it with ‘X’ (first player) or ‘O’ (second player)
The winner: first player to mark a row, column or diagonal
Variant: board is marked with numbers from 1 to 9
The winner: first player to mark squares adding up to 15
The Chicken Challenge
Tropicana (Atlantic City, Las Vegas)Beat the chicken, win $10,000
(formerly side shows, NYC Chinatown. . .)
MENACE:a set of boxes & beads learns tic-tac-toe...
Matchbox Educable Noughts and Crosses EngineDonald Mitchie, Edinburgh, 1964One matchbox for every possible game positionNine colors of beads, corresponding to nine movesInitial state: each box holds one bead of each (legal) color“Engine” : choose random bead from current box
(and set it aside next to its box)At the end of the game:
If MENACE loses, discard all the beadsIf MENACE wins, put back three copies of each bead
Early example of “reinforcement learning” algorithm
Tic-tac-toe lessons
• The same problem can be viewed in different ways– addition game: finding numbers to sum to 15– tic-tac-toe 1: “owning” a row/column/diagonal– tic-tac-toe 2: learned response to any of 300 positions
• Ginger the chicken• MENACE
• Different views lead to– different kinds of solutions– different degrees of difficulty
• for different skill sets• in different dimensions
• A motivation for specialized formsof information representation & processing
– biological– individual– cultural
Types of human memory
• Faces/places/words/...• Semantic/episodic/motor
= facts/events/skills• Short term/long term• Different
– behavioral characteristics– brain localization– clinical syndromes
How many kinds?
• Proliferation of hypotheses about memory subsystems – Different semantic memory areas for
animals/tools/etc. ?• clinical dissociations
• “priming” by associative connections
– Or unified semantic memory systemwith differing cross-modal connections? (Farah 1994)
– Different short- and long-term memory stores?– Or various mechanisms for modulation of attention? (Cowan 2000)
One idea about STM
• Representational basis: – activated part of LTM– not a separate “memory buffer”
• Neurobiological network– Frontal attention control systems maintaining posterior LTM
meaning representations in an activated state– LTM is “weight based”; STM is “activation based”
Semantic Short-term Memory
• Maintains small set of word meanings in heightened state of activation
• Distinct from “phonological loop”• Distinct from “syntactic working memory”
Haarmann et al. 2002
Neural network model of (semantic) STMHaarmann & Usher, 2001
HippocampusMedial temporal(episodic LTM)
Posterior system(semantic LTM)
Capacity-limitations on recency effects in semantic STM
• Task
– Category cued recall task
– Word pool: 6 semantic categories, 4 words each
– Example of trial: fan, car, lime, rat FRUIT? “Lime”
• Design
– List length (4, 6 words) X Serial position of probed word
Individual differences in Semantic STM spanpredict memory load effects
in on-line semantic anomaly judgment:
0.5
0.6
0.7
0.8
0.9
1
short long
Distance
Pe
rfo
rma
nc
e (
A')High span
Mid span
Low span
(Haarmann, Davelaar, & Usher, 2002)
Long: He was concerned about the heavy long steep narrow footpath strewn with rocks
Short: The boys admired the curly, new car of the secretary in the office.