Presentation on

“On the Reliability of Implicit and Explicit Memory Measures” by Axel

Buchner and Werner Wippich

- Leonard Läer

- Philipp Schleenvoigt

- Ulrich Süß

byby

Table of ContentsTable of Contents

PART I - INTRODUCTIONPART I - INTRODUCTION

• Main statement of the articleMain statement of the article

• What is this reliability thing, anyway?What is this reliability thing, anyway?

• The role of reliability of memory testsThe role of reliability of memory tests

• Reasons for reliability differences between memory measuresReasons for reliability differences between memory measures

PART II - THE EXPERIMENTSPART II - THE EXPERIMENTS

• Experiment 1aExperiment 1a

• Experiment 1bExperiment 1b

• Experiment 2Experiment 2

• Experiment 3Experiment 3

PART III - CONCLUSIONSPART III - CONCLUSIONS

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - TABLE OF CONTENTS

PART I - INTRODUCTIONPART I - INTRODUCTION

MAIN STATEMENT OF THE ARTICLEMAIN STATEMENT OF THE ARTICLE

• former tests seemed to reveal functional dissociations between former tests seemed to reveal functional dissociations between explicit and implicit memory:explicit and implicit memory:

• older subjects (amnesic / distracted) perform worse than younger older subjects (amnesic / distracted) perform worse than younger (“normal” / undistracted) subjects in explicit memory tests, but (“normal” / undistracted) subjects in explicit memory tests, but nearly equal in implicit memory testsnearly equal in implicit memory tests

• but: same results possible if the reliability of the explicit memory tests but: same results possible if the reliability of the explicit memory tests were better than that of the implicit ones!were better than that of the implicit ones!

do our “found” dissociations only occur due todo our “found” dissociations only occur due tomethodological reasons?methodological reasons?

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - INTRODUCTION

WHAT IS THIS RELIABILITY THING, ANYWAY?WHAT IS THIS RELIABILITY THING, ANYWAY?

• in classical test theory we have:in classical test theory we have:

• a true score of some feature we want to measurea true score of some feature we want to measure

• an observed score of that featurean observed score of that feature

• aa measurement errormeasurement error

• the higher the error variance, the worse is the correlation between the the higher the error variance, the worse is the correlation between the true score and the observed scoretrue score and the observed score

• a test with a lower error variance is thus more reliablea test with a lower error variance is thus more reliable

reliability is the strength of the relation between reliability is the strength of the relation between observed and true scoreobserved and true score

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - INTRODUCTION

THE ROLE OF RELIABILITY OF MEMORY TESTSTHE ROLE OF RELIABILITY OF MEMORY TESTS

• testing groups that vary in their memory abilities, we should expect:testing groups that vary in their memory abilities, we should expect:

• to find larger differences in observed scores when using highly to find larger differences in observed scores when using highly reliable testsreliable tests

• to find lower differences in observed scores when using badly to find lower differences in observed scores when using badly reliable testsreliable tests

• assuming we use equally reliable tests for explicit and implicit assuming we use equally reliable tests for explicit and implicit memory, the same results (large difference for one, low difference for memory, the same results (large difference for one, low difference for the other “system”) would have been to be interpreted as a functional the other “system”) would have been to be interpreted as a functional dissociation between these two systemsdissociation between these two systems

• however, assuming our tests for explicit memory are more reliable however, assuming our tests for explicit memory are more reliable than those for implicit memory, we have to consider the possibility that than those for implicit memory, we have to consider the possibility that there is no functional, but a methodological reason for these resultsthere is no functional, but a methodological reason for these results

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - INTRODUCTION

REASONS FOR RELIABILTY DIFFERENCES IN MEMORY REASONS FOR RELIABILTY DIFFERENCES IN MEMORY MEASURESMEASURES

• reliability differences in memory tests due to:reliability differences in memory tests due to:

• differences in instructionsdifferences in instructions

• rigidity of goalsrigidity of goals

• possible strategies to achieve solutionpossible strategies to achieve solution

• usual implicit memory tests:usual implicit memory tests:• many possible solution many possible solution strategiesstrategies

• loosely defined goalsloosely defined goals

• usual explicit memory tests:usual explicit memory tests:

• few possible solution few possible solution strategiesstrategies

• clearly defined goalsclearly defined goals

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - INTRODUCTION

PART II - THE EXPERIMENTSPART II - THE EXPERIMENTS

1. experiment that typically leads to the dissociation 1. experiment that typically leads to the dissociation assumptionassumption

learning phase:learning phase:

• two groups of participants (n=42 each) two groups of participants (n=42 each)

• list of 92 nounslist of 92 nouns • each noun appeared for four seconds on screeneach noun appeared for four seconds on screen

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

one hour break... one hour break...

test phase:test phase:

• explicit memory group: word recognition (yes/no)explicit memory group: word recognition (yes/no)

“ “decide whether the noun appeared in the list.”decide whether the noun appeared in the list.”

• implicit memory group: word-stem completion (priming implicit memory group: word-stem completion (priming score) score)

“ “form any regular word from the following wordform any regular word from the following word -stems.” -stems.”

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

results:results: hit-rate split-half correlation hit-rate split-half correlation ( reliability) ( reliability)

word recognitionword recognition 77%77% 88 88

word-stem completionword-stem completion 12% 3512% 35

0

0,2

0,4

0,6

0,8

1

reliability

recognition word-stem

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

2. experiment confirms assumption about reliability2. experiment confirms assumption about reliability

learning phase:learning phase:

• one group of participants (n=42 each) one group of participants (n=42 each)

• list of 92 nounslist of 92 nouns • each noun appeared for four seconds on screeneach noun appeared for four seconds on screen

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

one hour break... one hour break...

test phase:test phase:

• explicit memory group: word-stem cued recallexplicit memory group: word-stem cued recall (priming score) (priming score)

“ “form words that appeared in the list from theform words that appeared in the list from the following word-stems.” following word-stems.”

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

results:results: hit-rate split-half correlation hit-rate split-half correlation ( reliability) ( reliability)

word recognitionword recognition 77%77% .88 .88

word-stem completionword-stem completion 12% .3512% .35

word-stem cued recall 62% .75word-stem cued recall 62% .75

0

0,2

0,4

0,6

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1

reliability

recognition word-stem cued recall

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

discussion:discussion:

explicit memory measures seem to have generally higher explicit memory measures seem to have generally higher reliability than implicit memory measures.reliability than implicit memory measures.

assumption:assumption: degree of reliability depends on the sum of degree of reliability depends on the sum of

- the number of possible strategies leading to solution:- the number of possible strategies leading to solution:• implicit memory strategies are numerous like completing word-stems implicit memory strategies are numerous like completing word-stems by reference to their graphemic-, phonological-, etc. properties. by reference to their graphemic-, phonological-, etc. properties.

• explicit memory strategies are less numerous due to more precised explicit memory strategies are less numerous due to more precised instructions.instructions.

- the number of possible solutions:- the number of possible solutions:• implicit memory tasks like free association normally do have many implicit memory tasks like free association normally do have many possible solutions.possible solutions.

• explicit memory tasks like word recognition do have a minor number explicit memory tasks like word recognition do have a minor number of possible solutions (eg. yes / no). of possible solutions (eg. yes / no).

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

there is light at the end of the tunnel...there is light at the end of the tunnel...

let’s try to equalize the reliabilities of the two let’s try to equalize the reliabilities of the two (implicit/explicit) memory tests(implicit/explicit) memory tests

use more restrictive instructions!use more restrictive instructions!

eg.: provide search strategy (eg. eg.: provide search strategy (eg. “try to find the solution “try to find the solution quicklyquickly.”.”), thus decreasing the number of strategies.), thus decreasing the number of strategies.

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

3. experiment equals reliabilities 3. experiment equals reliabilities

learning phase:learning phase:

• two groups of participants (n=32 each) two groups of participants (n=32 each)

• list of 50 pictureslist of 50 pictures • “ “name each picture appearing on screen as quickly as name each picture appearing on screen as quickly as a a possible.”possible.”

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

test phase:test phase:

• explicit memory group: picture recognition (yes/no)explicit memory group: picture recognition (yes/no)

“ “decide whether the picture appeared in the list.”decide whether the picture appeared in the list.”

• implicit memory group: fragmented pictureimplicit memory group: fragmented picture identification (priming score) identification (priming score)

“ “identify picture as quickly as possible and withidentify picture as quickly as possible and with a minimal number of steps in the defragmentation a minimal number of steps in the defragmentation procedure.” procedure.”

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

results:results: hit-rate split-half correlation hit-rate split-half correlation ( reliability) ( reliability)

word recognitionword recognition 77%77% .88 .88

word-stem completionword-stem completion 12% .3512% .35

picture recognition 90% .41picture recognition 90% .41

picture identification 115% .44picture identification 115% .44

0

0,2

0,4

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0,8

1

reliability

recognition word-stem recognition identification

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

conclusion:conclusion:

these results are compatible with the hypothesis that the these results are compatible with the hypothesis that the reliability of the measures derived from implicit memory reliability of the measures derived from implicit memory tests need not necessarily be smaller than that of the tests need not necessarily be smaller than that of the measures derived from explicit memory tests. rather, measures derived from explicit memory tests. rather, implicit memory measures may be at least as reliable as implicit memory measures may be at least as reliable as explicit memory measures, provided that the testsituation explicit memory measures, provided that the testsituation implied by the implicit memory tests is restrictive enough.implied by the implicit memory tests is restrictive enough.

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS

general discussion:general discussion:

should one neglect the dissociation theory because of this should one neglect the dissociation theory because of this

results?results?

no, but the problem we face here seems serious.no, but the problem we face here seems serious.

so, the problem can only be reduced to the degree to which so, the problem can only be reduced to the degree to which highly reliable implicit memory measures are used in highly reliable implicit memory measures are used in conjunction with sufficiently large sample sizes.conjunction with sufficiently large sample sizes.

ON THE RELIABILITY OF EXPLICIT AND IMPLICIT MEMORY MEASURES - THE EXPERIMENTS