Case studies

Revision card case studies for AS Psychology

Peterson and Peterson- Duration of STM

Aim- To find out the duration of STM when rehersal is prevented

Procedure- They took participants and asked them to remember three letter congruent trigrams. They were then asked to count back in threes from a certain number after breaks of between 3 and 18 seconds. This was to prevent rehersal from taking place.

Findings- They found that after 3 seconds 80% of the trigrams could be  correctly remebered however, after 18 seconds less than 10% of the trigrams could be correctly recalled.

Conclusions- They concluded that the duration of STM must be between 15-18 seconds. Also if information is not rehersed then it vanishes from STM.

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Elizabeth Loftus- Smashed headlight

Aim- To see how the accuracy of eye witness testimony changed by leading questions

Procedure- 45 students were shown a video of a car crash. They were then split into 5 or 6 different groups and asked questions about how fast the car was going. Instead of the word fast some of the groups had other adjectives such as smashed, bumped collided, contacted.

Findings- Those who got the word contacted estimated a speed of about 31mph whereas those who got a speed of smashed estimated 41mph 10 more than others even though they had seen the same video.

Conclusions- This showed that ewt was generally inaccurate and unreliable. However, this study has helped to improve techniques now about leading questions.

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Karpel et al - Eye witness testimony in elderly

Aim- To see how reliable eye witness testimony is in older people.

Procedure- Young adults and older adults were shown a video of a robbery. They were asked what they had seen and the information was compared.

Findings- Young adults gave more accurate information and were less vulnerable to leading questions.

Conclusions- Young adults will make more reliable eye witnesses.

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Martin et al- Eye witness testimony in children

Aim- Test age difference between children and young adults.

Procedure- Primary school, secondary school and college aged students saw a 15 second scene of a distressed man. They were tested on the information straight after and two weeks later.

Findings- Recall of both correct and incorrect information increased with age and no difference in accuracy and influence of leading questions.

Conclusions- Although younger children recalled less information key information was unaffected.

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Elizabeth Loftus- Weapon study

Aim- Whether and eye witness would remember the centeral details if a weapon was involved.

Procedure- They took participants and used two different conditions. In one condition the man was carrying a pen covered in grease and in the other a man had a paper knife covered in blood. Participants were then asked to identify the man from a line up of 50 photos.

Findings- Participants asked in condition one 49% correctly identified the man however, in condition two only 33% correctly identified the man.

Conclusions- This study suggested that the weapon may have distracted from the face of the person carrying it which is very important. This could explain why sometimes eye witnesses have poor recall especially in violent crimes.

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