Transcript slides

Learning Where to Look: An
ACT-R/PM Model
Brian D. Ehret
ARCH Laboratory
Human Factors and Applied Cognition
George Mason University
ACT-R Workshop - August 7, 1999
Overview
HCI research has demonstrated that users learn
the locations of interface objects
However, not much known about mechanisms
underlying location learning
Systematically vary conditions under which
location learning may occur in order to
Infer characteristics of location learning mechanisms
Embed these characteristics into a computational
cognitive model using ACT-R/PM (Byrne & Anderson,
1998)
Color-Match Condition
Meaningful Text Condition
Arbitrary Icon Condition
Performance Time Results
16
14
16
Arbitrary
Color-Match
Meaningful
14
Trial Time (sec)
No-Label
12
12
10
10
8
8
6
6
4
4
2
2
0
0
1
2
3
4
5
6
7
8
9
Blocks
10
11
12
13
14
15
16
Overview of Model
35 rules for all four conditions
20% of rules common to all four conditions
Overlap between conditions ranges from
23% between Color-Match and Arbitrary to
86% between Arbitrary and No-Label
Interacts directly with software via ACT-R/PM
Relies on search vs. retrieve paradigm
Akin to compute vs. retrieve (arithmetic facts)
Preference for less costly strategy
Overview of Model (cont’d)
Declarative structures
Buttons
Locations
Labels
Colors
Learning Parameters
Base level learning (d=0.3)
Merging and retrieval
Associative strength learning (:al=1)
Source spread
Search Cost and Strategies
Search Cost - number of buttons evaluated per
trial
Search Cost - Buttons Evaluated
7 7
Arbitrary
Color-Match
6 6
Number of Buttons Evaluated
Meaningful
No-Label
5 5
4 4
3 3
2 2
1 1
0 0
1
2
3
4
5
6
7
8
9
Blocks
10
11
12
13
14
15
16
Search Phase Summary
Pre-attentive Search
Search for location of button with correct color
ACT-R/PM find-location command
Controlled Search
Attempt to retrieve a past use of the correct button and
its associated location chunk
If retrievals fail, attend to random button
Retrieval attempted first (search vs. retrieve)
Evaluation Cost and Strategies
Evaluation Cost - time required to determine if
currently attended button is currently needed
Evaluation Cost - Time Per Button
2.4 2.4
Arbitrary
2.2 2.2
Color-Match
Meaningful
Average Time Per Button (sec)
2 2
No-Label
1.8 1.8
1.6 1.6
1.4 1.4
1.2 1.2
1 1
.8 .8
.6 .6
.4 .4
1
2
3
4
5
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8
Blocks
9
10
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12
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Evaluation Phase Summary
Color-Match and Meaningful always label
match
Arbitrary label matches only if label retrieved in
search phase
No-Label and Arbitrary (if label not retrieved)
try location assessment
Attempt to retrieve a past use of the currently
attended button and its associated location chunk
If retrievals fail, then wait for ToolTip
Retrieval attempted first (wait vs. retrieve)
Implications
Locations encoded as a by-product of attention
Default ACT-R/PM behavior
Location knowledge, once encoded into memory,
is like any other knowledge
Subject to the same learning mechanisms
Task performance characterized as rational
Attempt less costly strategies first
Pre-attentive < retrieve location < search
[search phase]
Label-match < location assessment < tip [evaluation phase]
Results in differential location learning