how it looks if decisions are made from memory

1

How it looks if decisions are made from memory

Arndt Bröder & Stefanie Schiffer (2003)Department of Psychology, University of Bonn

broeder@uni-bonn.de

Thanks to:Jutta Bierwirth, Arvid Herwig, Andrea Kurth, Susanne Neufang &

Nathalie Ziegler (data collection)DFG (funding)

2

Overview

The Adaptive Toolbox idea Take The Best and other heuristics The „Memory Search“-Hypothesis

Experiment 1: Pilot study Experiment 2: Memory vs. screen

The Format-Hypothesis Experiment 3: representational format

Summary & Perspective

3

1. The Adaptive Toolbox

Gigerenzer & Selten (2001) view the human mind as an „adaptive toolbox“ with domain-specific simple heuristics that follow simple decision rules („fast“), need little information („frugal“), and are applied adaptively.

4

Open questions (selection):

Selection mechanism for heuristics? („meta-rule“)

Status of toolbox: Theory? Framework? Applicability? Empirical Predicitions?

Empirical evidence?

5

2. The „Take The Best“-Heuristic Domain: probabilistic inferences with uncertain

knowledge

Which way leads to the city center: Left or right? Which share will be more profitable: Volkswagen or BMW? Which nation has a higher per capita GDP: Norway or Spain? Which city has more inhabitants: Heidelberg or Bonn? Which food contains more cholesterol: Fish `n Chips or pumpkin

pie? etc.

Make a „best guess“ according to probabilistic cue knowledge

How is the cue knowledge integrated?

6

Example Which European country has the higher per capita GDP?

Take The Best (TTB): „Spain“ Noncompensatory, little info required, ordinal cue weighting

Weighted Additive Strategy (COMP): „Norway“ Compensatory, high info requirement, absolute cue weighting

Majority Rule (EWL): „Norway“ Compensatory, medium info requirement, no cue weighting

Cue Spain NorwayMember of European Union? yes no

Unemployment rate <10% ? no yes

Trade balance positive ? no yes

Inflation <3% ? no yes

7

TTB: Empirical Evidence

Few Studies concerning TTB & LEX: Rieskamp & Hoffrage (1999) Bröder (2000 ; JEP:LMC) Newell, Weston & Shanks (2001) Läge, Christen & Daub (2002) Newell & Shanks (2003; JEP:LMC) Newell, Rakow, Weston & Shanks (in press) Bröder (in press, JEP:LMC)

(COARSE-GRAINED!) SUMMARY: TTB appears to belong to the toolbox. The „default“, however, seems to be a compensatory strategy

which is only abandoned in the case of high information costs (relative to gains)

8

3. The „Memory Search“-Hypothesis The standard experimental paradigm in multi-attribute decision

research (Structural Modeling as well as Process Tracing) consists of presenting all relevant attribute information to the participant.

Gigerenzer & Todd‘s criticism (1999): "we refer to this type of task as inference from givens, as

opposed to inference from memory or inference from the external environment, both of which require search. (...) [E]xperiments in which search is obviated are unsuitable for testing models of ecological and bounded rationality that rely on limited information search as a central component." (p. 23)

MSH: TTB (and other fast and frugal heuristics) will be used when inference is from memory

9

My criticism:

The authors do not even give a hint how this memory search hypothesis could be tested empirically.

Therefore, this looks like an attempt to make the „fast and frugal“ framework immune to empirical critique!

Increasing the precision of a hypothesis involves delineating constraints and deriving new predictions.

10

Methodical problems & solutions:

Problem 1: Participants‘ knowledge base must be known to the experimenter Participants learn attribute patterns of objects

by heart

Problem 2: How can strategies be inferred when (a) response errors are allowed and (b) Process Tracing is impossible? Bayesian model selection method based on

likelihood of empirical choice vectors, given the models (=measurement model)

11

Paradigm Criminal story:

A popular singer was murdered by one of his 10 former lovers...

12

LEARNING PHASE

(10 suspects with 4attributes each)

Build up knowledgebase in memory

Information about critical attributes

DECISION PHASE

Integrate cue infor- mation in memory

13

Experiment 1: Pilot study

Aim: Material testing: Can it be learned in a reasonable amount

of time? Do participants use TTB when deciding from memory?

Participants: 50 Students of Bonn university (35f, 15m, age 25.5)

14

Learning phase

15

Decision Phase

16

Results Experiment 1

64% (!) of participants classified as TTB users estimated reponse error rate: 18%

Strategy classifications (%)

64

12 12 12

0

10

2030

40

50

60

7080

90

100

TTB COMP EWL GUESS

17

Discussion Experiment 1

Surprisingly high rate of TTB-users seems to confirm the MSH

Caveat: Maybe a materials effect! A direct comparison of „inference from givens“ and „inference from memory“ is necessary.

18

Experiment 2: Memory vs. Screen

Design: „Inference from memory“ (replication of Study 1) vs. „Inference from givens“ (attribute information

available on the screen)

Participants: 50 Students of Bonn University (35f, 15m, age

24.1)

19

Results of Experiment 2

Less TTB-users than in Experiment 1(n.s.), but significant difference between conditions (2

(2)=6.25; p<.05; w=0.35)

Estimated response errors: 26% vs. 8% (t(48)=7.33, p<.05)

Strategy classifications

4432

168

20

60

20

00

102030405060708090

100

TTB COMP EWL GUESS

memory screen

20

Discussion concerning the MSH

The Memory Search Hypothesis of Gigerenzer & Todd (1999) was corroborated.

In line with other studies this suggests that memory search causes subjective costs which trigger the use of „fast and frugal“ heuristics

Question: Is search in memory always costly?

21

4. The Format-Hypothesis TTB is a sequential heuristic.

Sequential retrieval is plausible for a verbal or propositional information format.

Image-based formats cause simultaneous retrieval of cue information which should trigger the usual preference for compensatory decision making.

Hence: Image-based representation may be a boundary condition for MSH

22

Experiment 3: Representation format

Design (simplified): verbal Cue-Info vs. image-based Cue-Info

Realization: Presentation of items in a way encouraging

holistic image-based encoding (Stimuli: www.otto.de, virtual dressing room).

Participants: 114 Students of Bonn University and other

volunteers (76f, 38m, age:24.4)

23

Learning (1)

24

Learning (2)

25

Learning (3)

26

Learning (4)

27

Learning (5)

28

Decision Phase

29

Results Experiment 3

Difference consistent with hypothesis (2

(2)=10.98, p<.01) estimated response error: 30%

Strategy classifications

47,4

13,2 13,226,326,4 31,8 27,6

14,5

0102030405060708090

100

TTB COMP EWL GUESS

verbal image

30

5. Summary

Summary: TTB belongs to the toolbox It is especially prevalent in decisions from memory

when this information is in a verbal/propositional format.

An image-based format leads to more compen-satory DM.

„cognitive algorithms (...) cannot be divorced from the data format on which they operate“ (Gigerenzer & Hoffrage, 1995, p. 710)

31

Perspective

Future projects

How adaptive is the toolbox? Precise formulation of boundary conditions and empirical testing Influence of habits and personality differences

Closer connection between decision research and other fields of cognitive pychology

representational assumptions working memory components

32

Thank you for your attention!

33

Appendix

Critical item Types

34

Item types: Critical evidence found at scene of crime: Blood type A, Marlboro cigarettes, Chanel perfume, limousine

blood type A 0 A 0 A 0

cigarettes Marlboro Marlboro Camel Marlboro Marlboro Marlboro

perfume Chanel Chanel Egoiste Chanel Chanel Chanel

vehicle convertible motorbike motorbike motorbike convertible limousine

TTB=COMP=EWL TTB≠(COMP=EWL) TTB=COMP; EWL=?

35

Does an image-based format exist?

Pro:

Con:

"BAUM"

Compromise: There is a special format of representation which also contains propositional information (Kosslyn, 1994). It is not a photograph-like copy of the physical world.