32Please draw as many of the pictures as you can Please write ‘1st group’ or ‘2nd group’ on your paper
33Experiment Please hand your drawing to a member of the other group Check to see whether the drawing looks like one of a pair of objects
34Curtains in a window or Diamond in a rectangle Bottle or stirrup Crescent moon or letter “C”Beehive or hatEye-glass or DumbbellsSeven or FourShip’s wheel or SunHour glass or TableKidney bean or CanoePine tree or TrowelGun or BroomTwo or Eight
35Reconstruction of Automobile destruction Elizabeth F. Loftus and John C. Palmer (1974)
36TheoryPeople are not good at reporting numerical details, such as time, speed and distance (Bird 1927).Marshall (1969) found that participants gave speed estimates ranging between 10 and 50 mph for a car travelling at 12mph!
37Theory(Block 1974) Because people are poor at estimating they can be easily influenced by questioning, for example. In courts of law leading questions can not be asked.Fillmore (1971) found that the words `hit' and `smashed' could affect the estimated speed.
38Experiment 1 Method 45 students in groups of various sizes Would the results generalise?Are they just trying to please their teacher?
397 films from the local safety council and police second film clips, of car accidents.Not really like a real accident, therefore lacks ecological validityAfter a written account of each accident was given by each student, a series of questions was asked.The critical question was one about the estimated speed of the vehicles.
40Experiment 1 - Method What was the purpose of the written account? Did this affect the results?Loftus & Palmer fail to report any details of what was writtenWhat data could have been obtained from these accounts?
41Experiment 1 - Method 5 groups of 9 students. Group sizes rather small Between 15 and 20 in each group is usually sufficientEach group had a different version of the critical question.
42Experimental Conditions 1. About how fast were the cars going when they hit each other?2. About how fast were the cars going when they smashed each other?3. About how fast were the cars going when they collided with each other?4. About how fast were the cars going when they bumped into each other?5. About how fast were the cars going when they contacted with each other?
43Independent VariableDifferent wording of the questions
47Experiment 1 - ResultsThese differences are significant at p is less thanThis means that less than five in every thousand times this experiment is run could the results possibly be owing to chance factorsAs chance results are unlikely we reject our null hypothesis
48Experiment 1 - Hypothesis It is predicted that there will be a significant difference between speed estimates depending upon the verb used in the question about speed.This is known as a two-tailed experimental hypothesis because we are just predicting a difference without saying which verb has the greatest effect on speed estimation.
49Experiment 1 - Did the actual speed of the cars affect the estimate
50Experiment 1 - Discussion 1. The participant is not sure of the speed so the verb provides the answer.2. The verb changes the memory representation.
51The results of experiment 1 suggest a research question for experiment 2. If the memory representation is changed then we might expect the participant to ‘see’ other things that were not actually there.
52Experiment 2 - Method150 students were shown a film of a multiple car crashThe film lasted one minute, but the action was just 4 seconds long.Three groups of 50 students were used.All students were asked to give a written description of the car accidentA series of questions was asked
53Experiment 2 - Critical questions · One group was asked: `About how fast were the cars going when they smashed into each other?'· The second group was asked `About how fast were the cars going when they hit each other?'· The third group were not asked about the speed.
54One week later The participants returned They did not see the film againThey were again asked a series of ten questions about the filmThe critical question was “Did you see any broken glass?”The participants checked a box labelled ‘yes’ or a box labelled ‘no’.
55Experiment 2 - MethodThe critical question appeared randomly in different positionsThere was no broken glass in the film
58Probability of saying that there was broken glass The verb ‘smashed’ affects speed estimate in a way that lies beyond saying that because ‘smashed’ suggests the cars were going fast when they crashed there must have been glass.
59Experiment 2 - Discussion Over time, perhaps, we are unable to tell the difference between information processed during perception and information received later.
60ImplicationsIf eye witnesses are so inaccurate then we must not allow a person to be convicted just on the basis of an eye witness report.Leading questions in court should also be avoided.
61CriticismsLacks ecological validity - not a real crash, paying attentionParticipants - students, young and intelligent, eager to please their lecturersDemand characteristics - they knew they were being studiedMay not be memory but just guess work based on information supplied