WEEK 2 - witnessing a crime

What is the role of the innocence project?

goes through cases and fundraises to look into it to see if the offender was actually guilty

what did the innocence project find was the biggest contributing causes to a wrongful conviction?

eyewitness errors

eyewitness evidence is what?

powerful and persuasive to juries and investigators

in the US how many people become defendants each year on the basis of eyewitness testimony?

77,000

what is the definition of exoneration?

convicted of a crime and DNA was not tested, so wrongfully convicted

perception leads to what?

memory

what 3 things is memory made up of?

retrieval, encoding and storage

what is perception?

the way we perceive a crime and interpret it

what is the 2468 task?

given three numbers and have to follow a rule - unaware what the rule is

what does your brain seek?

to confirm what it wants to believe

our perception of stimuli and our reaction to them depends on what?

• past experiences

• stereotypes

• expectations

• beliefs

• knowledge

what are schemas?

beliefs and expectations concernign the nature, characteristics, behaviours or functions of objects, people and events

how are schemas activated?

by others, statement from others, (e.g stop theiff) stimuli

give an example in a case where there was potential error with the scehma

david bain

thought he said “i shot the prick”

people hear what they want to hear

Fraser (2011) conducted a study on potential for error, what did his study consist of?

• randomly assigned to one of two groups

• a - primed to belive david shot hsi whole family

• b - primed to believe that davids father shot the whole family

• opinion on what was said in the audio was sought at 7 different time points

what did frasers study find?

both groups were the same up until stage 4

stage 4 = when they heard i shot the prick or he shot them all

participants perception of the tapes contents were significantly influenced by the info they had been given

only four people in group b - heard i shot the prick - two were police officers and one was a forensic psych student

what are the two cases that highlight the potential for error and that people payed the consequences?

trayvan vs george

oscar vs reeva

payne (2011) also conducted a study ont he potential for error what did their study consist of?

participants were primed with either a black or white face and then asked to classify objects as tools or weapons

what did paynes study conclude?

those primed with black faces were wuicker to categories weapons

when forced to respond quickly - those primed with black faces were more likely to mistakenly identify tools as weapons

the reverse was true for those primed with a white face

correl, park and wittenbank (2002) conducted a study on potential for erros and looked at computer simulation what did the study consist of? what did they find?

participants were aked to shoot only targets holding weapons

participants more likely to shoot at unarmed black people than unarmed white people

even police officers showed bias

what are the implications for eyewitnesses?

• environmental/health conditions e.g short sighted, dark

• expectations/experiences e.g what we perceive, how we interpret it

a lack of recall is not neccessary what?

a retrieval problem

what factors can influence encoding?

• attention

• salience

• stress/arousal

• presence of a weapon

leippe,wells and ostrom conducted a study on the effect of salience, what did the study consist of? what did they find?

staged a theft in front of a group of students

Thieved item was either expensive or trivial

found:

• eyewitness made more accurate identifications when the crime was perceived as more serious

what did they manipulate in this study to test that the results were due to increased encoding? what did they find after this manipulation?

manipulated whether or not the value of the expensive item was known at the time of the robbery.

when value knowledge was gained after the robbery, the effect was not observed

yerkes dodson suggest that _____% of eyewitnesses experts believe that stress has a negative effect on memory accuracy

64%

yerkes dodsons law shows what trend?

an inverse U

asleep-panic

however this evidence is controversial

loftus and burns looked at a study of the effect of stress/arousal and showed participants a short movie of a bank robbery with either a violent or non violent ending, what was found?

violent version = poorer memories for the detail see immediately before the violence

wessel and merkelbach conducted a study where they exposed peopel with or without a spider phobia to a live spider in a jar, what was found?

memory for central events - did not differ between the two groups

memory for peripheral details - spider phobic participants scored lower

who looked at the cue utilisation theory? what does it suggest?

james easterbrook

people can only attend to a limited number of cues at any oen time. As stress increases, their attention narrows to the stress-generating features

its easy to study the effect of stress?

no false it is hard

what would the perfect study of stress/arousal look like?

• situation is ecologically valid

• experince is controllable

• degree of stress can be manipulated

• stress response is measured

• can evaluate accuracy

How can stress response be measured?

HR, cortisol, skin conductance

Morgan et al conducted a study on elite soldier trainees, what did the study consist of and what did they find?

captured and taken to mock POW camp

high vs low stress interrogations

identification test 24 hrs later

mistaken identifications were made by 51-68% of those under high stress and 12-38% under low stress

what is the weapon focus effect?

visual attention that eyewitnesses give to the perpetrators weapon during the course of crime

loftus conducted a study on the weapon focus effect - participants saw slides of a customer pullling out a gun or a chequebook. What was found?

participants made more correct identifications in the no weapon condition

participants made more and longer eye contact on the gun thana chequebook

even in a harmless situation, witnesses eyes are drawn to a weapon? true or false?

true

pickel conducted a study on the weapon focus effect and gave participants slides of a target dressed either as a policeman or a priest, carring either a gun or cell phone. What was found?

witnesses were less accurate about the priest when he carried a gun

memory accuracy for the policeman did not differ according to the prop he carried

what things can chnage what gets in and how it varys strength?

• amount of exposure

• salience

• age

• knowledge

what are the implications for eyewtinesses (encoding)?

• soemtimes cant remeber things simply because they were never encoded in the first place

• numerous factors influence whether or not perceived infromation is encoded and how strongly information is encoded