Cognitive Models CS 160 Spring 2003 February 24

Cognitive Models CS 160, Spring 2003 February 24, 2003 2/11/2002 1

Why Model Human Performance? 4 To test understanding 4 To predict influence of new technology 2/11/2002 2

Model Human Processor 2/11/2002 3

What is missing from MHP? 4 Haptic memory * for touch 4 Moving from sensory memory to WM * attention filters stimuli & passes to WM 4 Moving from WM to LTM * rehearsel 2/11/2002 4

MHP Basics 4 Based on empirical data * years of basic psychology experiments in the literature 4 Three interacting subsystems * perceptual, motor, cognitive 4 Sometimes serial, sometimes parallel * serial in action & parallel in recognition + pressing key in response to light + driving, reading signs, & hearing at once 4 Parameters * processors have cycle time (T) ~ 100 -200 ms * memories have capacity, decay time, & type 2/11/2002 5

Memory 4 Working memory (short term) * small capacity (7 ± 2 “chunks”) + 6174591765 vs. (617) 459 -1765 + DECIBMGMC vs. DEC IBM GMC * rapid access (~ 70 ms) & decay (~200 ms) + pass to LTM after a few seconds 4 Long-term memory * huge (if not “unlimited”) * slower access time (~100 ms) w/ little decay 2/11/2002 6

MHP Principles of Operation 4 Recognize-Act Cycle of the CP * on each cycle contents in WM initiate actions associatively linked to them in LTM * actions modify the contents of WM 4 Discrimination Principle * retrieval is determined by candidates that exist in memory relative to retrieval cues * interference by strongly activated chunks 2/11/2002 7

The Model Human Processor Long-term Memory Working Memory sensory buffers Eyes Ears 2/11/2002 Visual Image Store Perceptual Processor Auditory Image Store Motor Processor Fingers, etc. Cognitive Processor 8

Principles of Operation (cont. ) 4 Variable Cog. Processor Rate Principle * CP cycle time Tc is shorter when greater effort * induced by increased task demands/information * decreases with practice 2/11/2002 9

Principles of Operation (cont. ) 4 Fitts’ Law * moving hand is a series of microcorrections + correction takes Tp + Tc + Tm = 240 msec * time Tpos to move the hand to target size S which is distance D away is given by: + Tpos = a + b log 2 (D/S + 1) * summary + time to move the hand depends only on the relative precision required 2/11/2002 10

Fitts’ Law Example Pop-up Linear Menu Pop-up Pie Menu Today Sunday Monday Tuesday Wednesday Thursday Friday Saturday 4 Which will be faster on average? * pie menu (bigger targets & less distance) 2/11/2002 11

Principles of Operation (cont. ) 4 Power Law of Practice * task time on the nth trial follows a power law + + Tn = T 1 n-a + c, where a =. 4, c = limiting constant i. e. , you get faster the more times you do it! applies to skilled behavior (sensory & motor) does not apply to knowledge acquisition or quality 2/11/2002 12

Power Law of Practice 2/11/2002 13

Perception 4 Stimuli that occur within one PP cycle fuse into a single concept * frame rate necessary for movies to look real? + time for 1 frame < Tp (100 msec) -> 10 frame/sec. * max. morse code rate can be similarly calculated 4 Perceptual causality * two distinct stimuli can fuse if the first event appears to cause the other * events must occur in the same cycle 2/11/2002 14

Perceptual Causality 4 How soon must red ball move after cue ball collides with it? * must move in < Tp (100 msec) 2/11/2002 15

Simple Experiment 4 Volunteer 4 Start saying colors you see in list of words * when slide comes up * as fast as you can 4 Say “done” when finished 4 Everyone else time it… 2/11/2002 16

Paper Home Back Schedule Page Change 2/11/2002 17

Simple Experiment 4 Do it again 4 Say “done” when finished 2/11/2002 18

Blue Red Black White Green Yellow 2/11/2002 19

Memory 4 Interference * two strong cues in working memory * link to different chunks in long term memory 4 Why learn about memory? * know what’s behind many HCI techniques * helps you understand what users will “get” * aging population of users 2/11/2002 20

Stage Theory 4 Working memory is small * temporary storage + decay + displacement 4 Maintenance rehearsal * rote repetition * not enough to learn information well 4 Answer to problem is organization * Faith Age Cold Idea Value Past Large * In a show of faith, the cold boy ran past the church 2/11/2002 21

Stage Theory maintenance rehearsal Sensory Image Store decay 2/11/2002 Working Memory decay, displacement Long Term Memory chunking / elaboration decay? interference? 22

Elaboration 4 Relate new material to already learned material 4 Recodes information 4 Attach meaning (make a story) * e. g. , sentences 4 Visual imagery 4 Organize (chunking) 4 Link to existing knowledge, categories 2/11/2002 23

LTM Forgetting 4 Causes for not remembering an item? * 1) never stored: encoding failure * 2) gone from storage: storage failure * 3) can’t get out of storage: retrieval failure 4 Interference model of forgetting * one item reduces ability to retrieve another * proactive interference (3) + earlier learning reduces ability to retrieve later info. * retroactive interference (3 & 2) + later learning reduces the ability to retrieve earlier info. 2/11/2002 24

Recognition over Recall 4 Recall * info reproduced from memory 4 Recognition * presentation of info provides knowledge that info has been seen before * easier because of cues to retrieval 4 We want to design UIs that rely on recognition! 2/11/2002 25

Facilitating Retrieval: Cues 4 Any stimulus that improves retrieval * example: giving hints * other examples in software? + icons, labels, menu names, etc. 4 Anything related to * item or situation where it was learned 4 Can facilitate memory in any system 4 What are we taking advantage of? * recognition over recall! 2/11/2002 26

Summary 4 MHP * three interacting subsystems? + perceptual, motor, cognitive * sometimes serial, sometimes parallel * parameters? + processors have cycle time (T = ~100 ms) + memories have capacity, decay time, and type * ten principles of operation (we showed 6) 4 Perceive distinct events in same cycle as one 2/11/2002 27

Summary (cont. ) 4 Memory * three types? + sensor, WM, & LTM * use cues in ? to get to ? + WM -> LTM * interference can make hard to access? + LTM 4 Cues can make it easier to access LTM 2/11/2002 28