Manipulating witnesses’ confidence in memory:

Implications for memory conformity

Fiona Gabbert, Amina Memon & Daniel B. Wright

Previous research

Archival data shows crimes often have more than one witness (Valentine et al., 2003; Wright & McDaid, 1996)

Where multiple witness are present, co-witness discussion is common (Paterson & Kemp, in press)

Challenge for researchers – to maximise ecological validity under controlled conditions

Typical finding = people’s memory reports become similar to one another’s following a discussion(Gabbert et al. 2003, 2004; Mori et al., 2003, 2004; Wright et al. 2000)

Current research

Does perceived memory quality influence susceptibility to memory conformity?

Experimental manipulation

Perceived encoding duration between dyad members is manipulated whilst actual encoding duration is held constant

Design: Between subjects design with 2 conditions (perceived encoding time; ½ vs. x2)

Participants: 88 (Mean age = 20 years) tested in dyads

Encoding material: 4 pictures of different scenes; 2 versions of each picture, each with 2 contrasting critical items - So, 8 critical items in total

Method

Procedure

DV = the amount of misinformation errantly reported at test

Coding

All co-witness discussions were transcribed

The transcriptions were coded to record which critical items were mentioned by each dyad member

The free recall scripts were coded for the number of 1) correct/errant neutral details from the pictures 2) correct/errant critical items

Results

Question 1Is there a difference in memory performance between conditions (half vs. twice perceived encoding duration) ?

Memory ability for neutral items

Pictures

Version A Version B

Perceived

encoding duration

Half the time 65.4 (20.1) 56.4 (18.3)

Twice the time 66.7 (17.8) 63.5 (17.5)

No main effects

Number of accurate neutral items recalled (SD in parentheses)

Results

Question 2Is there a relationship between perceived memory quality and memory conformity?

Effects of perceived memory quality

* p<0.05

Average number of critical items reported in each condition

00.5

11.5

22.5

3

3.54

4.55

accurate critical itemsreported

errant (co-witness)critical items reported

Perceived encodingduration HALF THETIME

Perceived encodingduration TWICE THETIME

*

*

Results

Question 3Is there a relationship between objective memory performance and memory conformity?

Actual memory ability & memory conformity

Susceptibility to co-witness influence was not related to memory for the pictures:

Influenced: 61.5 (SD = 18.1) accurate itemsNot influenced: 66.1 (SD = 19.5) accurate items

Correlation between number of accurate items of neutral information reported and number of errant co-witness details reported: r = .04, ns.

Discussion

Why does perceived memory quality mediate memory conformity?

It is possible that the feedback influences confidence in one’s memory (e.g., Wells & Bradfield, 1998)

This could affect metacognitive judgements about memory validity (e.g., Koriat & Levy-Sadot, 1999; 2000)

Email me at f.gabbert@abdn.ac.uk

• For a copy of the accompanying paper

• For a copy of the stimuli used• With any q’s or comments about

co-witness research

thanks

Source judgements attributed to errant critical items reported at test

Errant (Saw in picture)

Accurate (Co-witness

told me)

Half the time 58.9 41.1

Twice the time 47.5 47.5