Memory 10:�Eyewitness Testimony

Homework:

Make notes from textbook on eyewitness testimony, particularly Loftus (1975)

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Read this website: http://www.rpi.edu/~verwyc/oh13.htm

and make notes on anything you think is relevant.

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Awareness Test

http://www.youtube.com/watch?v=Ahg6qcgoay4

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Eyewitness Testimony

Brown stated that whilst judges believe EWT to be the least trustworthy evidence, jurors find it more persuasive than any other evidence

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Why do you think this is?

Something to think about…

• The Devlin Report found that there were 850 cases where EWT was the only evidence.
• In 74% of these cases, the accused was found guilty by the jury
• The Devlin Committee considered the reliability of such testimony and advised that no jury should convict on EWT alone
• In the USA many prisoners who were convicted by EWT have been released since DNA testing has been used, and they were discovered innocent of the crime

In real life…

Eyewitness testimony is often vitally important in deciding whether someone is found guilty of a crime.

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But how reliable is it?

Eyewitness Testimony

The evidence provided in court by a person who witnessed a crime, with a view to identifying the perpetrator. The accuracy of eyewitness recall may be affected during initial encoding, subsequent storage and eventual retrieval.

What factors can influence EWT?

• Encoding: Information added after event but recalled as part of the event
• Storage: Assumptions recalled as facts
• Retrieval: Information added at retrieval to make sense of event, wording of questions at retrieval

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Leading questions

• Loftus & Zanni (1975) – broken glass

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Leading questions:

• Group A: Did you see any broken glass?
• Group B: Did you see the broken glass?

Key Study

Eyewitness testimony

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Loftus and Palmer (1974)

Aims

• Investigate the accuracy of memory after witnessing a car accident,
• In particular to see if leading questions distort the accuracy of an eyewitnesses’ immediate recall.

Procedures

• 45 students
• Shown films of traffic accidents.
• Random questions afterwards, including the question:

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Can you estimate the speed of the car when it hit / smashed / collided / bumped / contacted with... {different words gave different experimental conditions}

Findings

Findings

• The group with ‘smashed’ estimated the highest speed (about 41 m.p.h.).
• The group given the word ‘contacted’ estimated the lowest (about 30 m.p.h.).

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Conclusions

Leading questions (post-event information) can have a significant effect on memory

Criticisms

• (1) Not true to life; recall more accurate in real life (Foster et al., 1994).
• (2) Demand characteristic – very hard to estimate speed so use any available clue.

Demand Characteristics

Anything that encourages the participant to act in a certain way – typically cues

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• Social desirability effects
• ‘Screw you’ effect

Leading questions – giving false information

Loftus et al (1978)

• Participants shown a short video
• Half of the participants saw a red Datsun approaching a STOP sign; the other half saw it approach a YIELD sign

Experimental conditions

Group 1. Participants who saw Stop sign

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Half the participants were asked a question referring to the stop sign (consistent condition)

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Half were asked a question referring to the yield sign (inconsistent condition)

Group 2. Participants who saw Yield sign

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Half the participants were asked a question referring to the stop sign (inconsistent condition)

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Half were asked a question referring to the yield sign (consistent condition)

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Both groups were later asked what sort of a sign the car was stopped next to.

The participants in the consistent condition were 75% correct in identifying the type of sign the car had been stopped by.

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Participants in the inconsistent condition were 41% correct in identifying the type of sign. (And lots of the ones who were wrong were convinced they were correct!)

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What can we conclude from this?

Pre-learned information (schemas)

• Frameworks for organising info
• Learned, may depend on culture and specific experiences.
• They can affect what info we store, and later recall

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Can you think of any examples?

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A little memory test for you:

Half of you close your eyes for a moment…

I’m going to show you some sentences that relate to flying a kite.

Here are your sentences

Write down as much of that as you can remember!

Bransford and Johnson

• Findings Participants who were given the title (‘Making and flying a kite’) did better at recall of text than those without the title.
• Conclusions: Having a way of categorising the information (a schema) improves organisation of information and aids recall.

Schemas

• A schema is an organised package of information containing our knowledge of the world, e.g. what to do when you go to a restaurant
• IF we encounter stimuli which conflict with our schemas, we reconstruct the memory to fit in with our schema – known as reconstructive memory
• Allport and Postman demonstrated this with an experiment …

Allport and Postman (1947)

• Allport and Postman showed participants a picture of a scruffy white man threatening a smart black man with a razor.
• Later they were asked to recall the picture
• Many recalled that a smart white man had been threatened with a razor by a scruffy black man.
• This fitted in with the American stereotypes of the time

Quick discussion break

Think about some of the things we have talked about already. How important do you think this research is in terms of memory in everyday life?

Another quick memory test…

I’m going to show you two lists of words – try and remember as many as you can.

List 1

Sour Nice

Candy Honey

Pie Sugar

Pop Bitter

Chocolate Good

Toffee Taste

Cake Tooth

Tart Sickly

List 2

Mad Wrath

Fear Happy

Hate Fight

Rage Hatred

Temper Mean

Fury Calm

Emotion Enrage

Annoy

Write down as many words as you can remember…

Just for fun…

http://www.psychexchange.co.uk/videos/view/20789/

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Schema theory - summary

• Bartlett suggested that the process of remembering is an active reconstruction of the bits that are stored
• Schema theory indicates that prior expectations will influence our perceptions
• Therefore our stereotypes will lead to changes in how we subsequently remember information

Tuckey & Brewer (2003)

Tuckey & Brewer (2003)

• AIMS: to see if schemas affect recall
• PROCEDURE: Collected people’s schemas for a bank robbery. Then asked eyewitnesses to recall events of a simulated crime they observed
• FINDINGS: Eyewitnesses to a bank robbery used their schema to assist in their recall of the robbery, especially when information was ambiguous.
• CONCLUSIONS: ambiguous detail is altered to fit in with a person’s robbery schema

Tuckey & Brewer (2003)

+ Demonstrates that memory is distorted by schemas

• It was not a real crime, so witnesses did not experience the same level of anxiety as in real life
• We do not know what an individual’s schemas are, so we cannot predict how people will interpret information

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Evaluation – schema theory

• Schemas influence the way data is stored and can explain how data is retrieved
• However, some psychologists believe that schema theory exaggerates inaccuracy of memories.
• We are capable of remembering things word for word, e.g. actors and actresses. Schema theory does not account for this
• Schema theory cannot predict what and how people remember information, because we cannot know which schemas are being used

Arousal

Loftus (1979) – Weapon focus effect

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• 49% accuracy in condition 1
• 33% accuracy in condition 2

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http://whs.moodledo.co.uk/mod/forum/discuss.php?d=6959&MoodleSession=6vjqk58gbogsgcfejpdipj54i3

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1.

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2.

Loftus et al (1987)

Partipants were asked to watch either:

• A person pointing a gun at cashier and receiving cash, OR
• A person passing a cheque to a cashier and receiving cash.

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In condition 1, fewer details were remembered because participants focused on the gun.

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Why is there a weapon effect?

• Not only does it pose a threat, but it is also unusual and unexpected

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• The weapons effect may be exaggerated. Evidence from 300 line ups did not find that presence of a weapon had any effect on correct identification

Consequences

• Participants shown video of bank robbery (Foster, 1994) and subsequently asked to identify robber
• One group believed it to be real event and that responses would influence trial
• Second group assumed it was simulation
• ID more accurate in group 1
• Conclusion?

Individual differences

Think about for next lesson…

How might individual differences between participants affect the reliability of eyewitness testimony?

Homework

Read and make notes from the textbook from everything covered today, plus the web link at the start of the powerpoint.