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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 [email protected]
• 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