Inductive reasoning and implicit memory: evidence from intact and impaired memory systems

Authors: Luisa Girelli, Carlo Semenza and Margarete Delazer.

Appeared in Neuropsychologia 42 (2004)

Review by: Sonja Damnjanovic

Introduction Inductive reasoning – process of

inferring a general rule by inspection of specific instances

Inductive reasoning is essential in problem solving, development of expertise and learning

Typical examples of inductive reasoning tasks are ‘series completion’ problems

Series completion problem

Letter or number series completion are given to participants (e.g. A C E G or 2 4 8 16)

The task is to discover a general rule, which defines the relations between constituent elements. The rule has to be identified and applied to continue given series!

Purpose of the study

To investigate role of implicit memory in problem solving

Previous studies show that number series completion may be facilitated by a priming procedure

Priming effects in number series completion

Presented studies Experiment 1 – A) explores the time course of priming in number series

completion. The number of intervening trials between prime and the target varied (4 and 10)

B) explores whether the trials were explicitly remembered or not

Experiment 2 – used just the lag 4 and was designed to examine which stage in number series completion is the most sensitive to priming

Case study – amnesic patient’s performance on number series completion task

Experiment 1 Number series completion task

Experimental trials were mixed with filler trials Both experimental and filler trials varied in difficulty Primes and targets were separated by four trials (block1) or by

10 trials (block 2). Task: say aloud what number comes next

Recognition task

Similar to series completion design, but following different criteria

Experimental trials were either identical prime-target pairs or pseudo-pairs

Task: Answer whether the trial was presented

before !

Experiment 1

Results

- reliable priming effect!

- faster and more accurate answers for target series then for primes series

- Lack of significant difference between priming effects in lag4 and lag10 conditions

(they are both pretty long for priming)

-Difficulty of the trial influenced accuracy - Easy trials (floor effect): low error rate for primes and

targets- Performance on recognition task was poor-

excluding strategies of explicit recollection

Experiment 2 1. Series completion task – identical to

the Experiment1

2. Identification task – identify the algorithm without completing it

3. Extrapolation task – (e.g.,”+2” for 2 4 6 8 ; participants were to say 10).

Experiment 2 results

Discussion Experiment 2

Question: Whether priming can be attributed to different processing components?

Identification task – participants were faster and more accurate in identifying rules for targets in comparison to the rules for primes

Difficult tasks yielded larger priming effects (my comment: probably easy items were too easy) Authors comments: completion of easy and difficult

series relies on different subprocedures

Experiment 2

Extrapolation task - significant priming for difficult items only My comment: easy items, too easy to catch

the difference between primes and targets Processing differences between easy and

difficult problems

Case study

Case of amnesia:

PR, 55 years old Performance on memory tests: Average WM span, impaired autobiographical

memory, severe deficits in learning verbal and visual information

Other results in the table

- Tasks were the same as in Experiments

1 and 2

Results:

Significant priming for lag 4 series completion task (p<.0001) in both difficult and easy trials

Not significant priming for lag 10

Identification tasks Significant priming for difficult (p< .01), but not for

easy trials

Extrapolation task No significant difference

Recognition task There is no evidence that he was able to explicitly

recognize previously presented trials

General discussion Studies support the view that priming occurs

via implicit memory activation. Participants did not explicitly recognized previously presented trials.

PR shows the evidence that the priming doesn’t occur due to explicit processes

Long lasting priming (because of the lag 10) But lag of 4 is also long

Comments: Experiment 1. Lag 4 and lag 10 are

arbitrary and not too different

Experiment 2. Not sure that the stages are measuring what underlies priming.

Case study. Sample size of 1 might not reflect what is really going on.