Cognitive Aging and Adaptive Strategy Selection - Supplemental Information 1
Supplemental Information for “The Aging Decision Maker: Cognitive Aging and the
Adaptive Selection of Decision Strategies”
Rui Mata, Lael Schooler, & Jörg Rieskamp
1. Using Elementary Information Processes (EIPs) to Quantify the Cognitive Demand of
the TTB, Take Two, and WADD Strategies
We computed the number of elementary information processes (EIPs; Payne, Bettman
& Johnson, 1993) each decision rule involves to quantify the cognitive effort associated with
the use of the different decision strategies considered in the study. The elementary
information processes considered were READ, COMPARE, ADD, MULTIPLY, GUESS, and
DECIDE. For example, per cue looked up, TTB required reading into a memory store two cue
values associated with each of the two options (READ), comparing these two (COMPARE),
and provided that this cue discriminated, making a decision (DECIDE). If the cue did not
discriminate, another two cue values were read and compared, and so on until a decision was
made or no more cues were available, leading the algorithm to choose randomly between the
two options (GUESS). WADD required reading each of the cue values on the two alternatives
(READ), multiplying each cue value with the cue’s predictive value (MULTIPLY), adding
this weighted cue value to the alternative’s tally (ADD), comparing the tallies of the two
alternatives (COMPARE), and making a decision (DECIDE) or guessing if the tallies did not
discriminate between alternatives (GUESS). The final EIP counts for the three different
strategies considered in our study are presented in Table S.1. The results reflect the different
cognitive demands implied in the use of TTB, Take Two, and WADD. An inspection of this
table shows a clear difference between strategies, with TTB and Take Two being the least
effortful due to their stopping information search when finding, respectively, one or two
pieces of discriminating evidence favoring an alternative. In comparison, WADD is the most
effortful strategy, always looking up all available information.
Cognitive Aging and Adaptive Strategy Selection - Supplemental Information 2
2. Cognitive Measures
The battery of 11 psychometric tests was administered to all participants. The tests
assessed various intellectual abilities including verbal knowledge (spot-a-word, vocabulary;
Lindenberger et al., 1993), processing speed (boxes, digit symbol substitution, identical
pictures; Lindenberger et al., 1993), reasoning (figural analogies, letter series, practical
problems; Lindenberger et al., 1993), and memory (operation span, Hamm, 2002; BrownPeterson task, Kane & Engle, 2000; forward digit span, Wechsler, 1981). A detailed
description of the psychometric properties of the tests can be found in the respective
references provided. In what follows we present a description of the tasks used to assess each
ability.
Verbal knowledge
Spot-a-word. Twenty items containing one word and four pronounceable nonwords
were presented successively on the screen. The task of the participants was to touch the word
on the screen. Three practice items were provided. The total number of words correctly
identified was the dependent measure (Lindenberger et al., 1993).
Vocabulary. Sixteen words were presented one-by-one on the screen and participants
had to explain their meaning. Participants’ answers were coded, each word receiving a score
of 0 (wrong), 1 (partially correct), or 2 (correct) (Lindenberger et al., 1993).
Processing speed
Boxes. Participants tapped for a limited time period (90 s) on boxes appearing at
different positions on a computer screen. Median time between taps was used as the
dependent measure.
Digit symbol substitution. Participants had to follow a scheme relating a set of symbols
to digits by writing below rows of digits as many symbols as possible within 90 s. A paperand-pencil format was used (Wechsler, 1981).
Reasoning
Cognitive Aging and Adaptive Strategy Selection - Supplemental Information 3
Identical pictures. In this task 32 items were presented. For each item, a target figure
was presented in the upper part of the screen and five possible responses were shown in the
lower part. As quickly as possible, participants had to touch the lower figure that matched the
target figure. Testing ended after 80 s. The dependent variable was the total number of correct
answers (Lindenberger et al., 1993).
Figural analogies. Items in this test followed the format “A is to B as C is to ?”.
Problems were presented in the upper part of the screen while possible answers were
presented in the lower part. Participants gave their answers by touching the screen
(Lindenberger et al., 1993).
Letter series. Sixteen items containing five letters followed by a question mark (e.g.,
“c e g i k ?”) were displayed in the upper half of the screen while five candidates to replace
the question mark were presented in the lower half (e.g., “p m l o n”). Items followed simple
rules, such as +1, -1, or +2. Participants gave their answers by touching the screen. The score
was based on the total number of correct answers (Lindenberger et al., 1993).
Practical problems. Twelve items depicting everyday problems such as interpreting a
bus schedule were used. For each item a problem was presented in the upper part of the screen
while five response alternatives were shown in the lower part. Participants gave their answers
by touching the screen. The test phase was terminated if participants made three consecutive
false responses, if they reached the time limit of 10 min, or when they answered the last item.
The total number of problems correctly solved was the dependent measure (Lindenberger et
al., 1993).
Memory
Operation span. The stimuli of Hamm (2002) were used for this task. Participants saw
individual operation–word strings (e.g., IS (8/4)-1=1? bear). They had to solve the math
problems, each of which was followed by a lowercase word, which was to be read aloud. On
hearing each word, the experimenter would press a key that would cause the presentation of
Cognitive Aging and Adaptive Strategy Selection - Supplemental Information 4
the next string. After a set of these operation–word strings, participants recalled the words.
The dependent measure was the cumulative number of words recalled from perfectly recalled
trials.
Brown–Peterson task. Participants viewed three lists of items from the category
“professions” followed by one list of the category “animals.” Between lists participants had to
recall the items. Additionally, before the recall they had to perform a distracting task
consisting of counting aloud from, for instance, D-32 (e.g., D-32, E-33, F-34) for 16 seconds.
The dependent variable was the difference between the numbers of correct items recalled in
the first and second list (see Kane & Engle, 2000). Higher values on this measure indicate less
resistance to proactive interference.
Forward digit span. This task corresponds to the Wechsler Adult Intelligence ScaleRevised digit span subscale (Wechsler, 1981). Sequences of digits with an increasing number
of elements (3–9 digits) were presented. The participants were instructed to recall the digits in
the correct sequence at the end of the presentation. After a correct response the number of
digits presented was increased by one. When the participants made a mistake, an alternative
sequence of the same length was shown. If the participant failed again, the test was finished.
The maximum number of correctly recalled digits was used as the dependent variable.
3. Strategy Classification
Our simulation results support the use of an outcome-and-search classification method
and we therefore relied on this classification procedure. The strategy that predicted the most
inferences correctly for a participant was assigned to the participant. Recall that TTB’s
stopping rule consists of stopping search after seeing the first discriminating cue. Take Two
involves stopping search after seeing two discriminating cues favoring the same alternative.
Finally, for WADD we assumed that all cue values had to be searched on both objects.
Participants for whom the fit of two or more strategies coincided were left unclassified.
To further examine the validity of our classification we determined to what extent the
Cognitive Aging and Adaptive Strategy Selection - Supplemental Information 5
different strategies could predict the final choices, search behavior, or both of participants
classified as TTB, Take Two, and WADD according to the outcome-and-search method (see
Table S.2). The strategy fit based on outcome only is similar to that reported by others (e.g.,
Bröder, 2000, with best fits falling in the [.63, .98] interval). The strategies’ fit in predicting
the search behavior was substantially lower compared to the fit in predicting the choices. One
plausible explanation is that search behavior is more loosely connected with the applied
strategy, for example, people may search for additional information to consolidate a
preliminary decision (see also Rieskamp & Otto, 2006). Supporting our classification method,
the strategy assigned to a group of participants was by and large better than the competing
strategies in predicting the decision, search, or both aspects of those participants’ behavior.
For example, for participants classified as TTB users, TTB could predict the decisions and
search for on average 40% of their trials compared with a fit of 4% and 1% for Take Two and
WADD, respectively. Consequently, the low fit values for the outcome-and-search method
are due only to the strictness of the method, which considers that both outcome and search
need to match to classify a trial as evidence for the use of a particular strategy.
Cognitive Aging and Adaptive Strategy Selection - Supplemental Information 6
Table S.1
Means and Standard Deviations of Elementary Information Processes (EIPs) as a Function of
Decision Strategy in our Experiment
Decision strategy
EIP
TTB
Take Two
WADD
M
SD
M
SD
M
SD
Read
143
6
349
11
800
0
Compare
72
3
174
6
50
0
Add
―
―
123
2
400
0
Multiply
―
―
―
―
400
0
Decide
50
0
50
0
50
0
Guess
―
―
―
―
2
2
Total
265
8
696
18
1702
2
Cognitive Aging and Adaptive Strategy Selection - Supplemental Information 7
Table S.2
Mean Fit of Strategies to Choices (Outcome only), Information Search (Search only), or Both
(Outcome and search) of Participants Classified as TTB, Take Two, or WADD According to
the Outcome and Search Method
Strategy users
TTB
Take Two
WADD
Outcome only
TTB usersa
.81
.65
.60
Take Two usersb
.76
.76
.70
WADD usersc
.68
.74
.79
Search only
TTB usersa
.43
.06
.02
Take Two usersb
.06
.22
.05
WADD usersc
.01
.02
.51
Outcome and search
TTB usersa
.40
.04
.01
Take Two usersb
.05
.19
.03
WADD usersc
.01
.02
.38
Note. an = 19; bn = 38; cn = 103. Each row of the table represents the fit of the strategy TTB, Take Two, or
WADD for one group of participants (TTB, Take Two, or WADD users as classified by the outcome and search
method).