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  1. 1. Bruce The importance of external and internal features in facial recognition Theories of interviewing witnesses
  2. 2. Background: • The facial composite technique involves witnesses putting together several components of a face by selecting the right eyes, eyebrows and nose etc from a selection of these features. • The IDENTIKIT was developed in the 1940’s in America. This was then developed into PHOTOFIT in England. • Internal features include the eyes, nose and mouth. • External features include the head shape, ears and hair.
  3. 3. Aim: • To investigate the relative recognisability of internal and external features in facial recognition.
  4. 4. Methodology: Experiment one: • 30 staff and students from Stirling university, paid £2 to sort the composites. 15 males and 15 females with a mean age of 29.2 • Independent measures design with 3 conditions.
  5. 5. Procedure: Experiment one: • All participants were given pictures of 10 celebrities and asked to match the correct composite image to the celebrity from the 40 composites given. • Composite images were made by E-FOT, PRO-fit, Skethc and EvoFit- all used b the police. • Group 1: Given complete composites. • Group 2: Given composites containing only internal features • Group 3: Given composites containing only external features. • Each face was clean shaven and avoided glasses.
  6. 6. Results: Experiment one: • 42% of whole composites and external features were sorted correctly. • Only 19.5% of internal composites were sorted correctly.
  7. 7. Procedure: Experiment two: • 48 undergraduates at Stirling university. 21 males and 27 females, all volunteers. • This experiment used a photo array, or photo line up. • The task was to identify the celebrity composites from the array. • The task was either made easy by having them very different to the target face, or made hard by having the composites all very similar to the target face. • The composites were either composed of internal or external features.
  8. 8. Results: Experiment two: • External features were identified 42% of the time, compared to just 24% of internal features.
  9. 9. Conclusions: • Participants performed equally as well for both whole composited and external features, but just over chance for internal features. • This shows that external features are more important for facial recognition and that faces are processed holistically.
  10. 10. Issues: • Reliability – Used already well established methods of making composites • Generalisability – All from one university – All volunteers- one type of personality- helping – An unbiased sample in terms of gender bias • Independent measures – Less demand characteristics – Participant variables present – Subjective
  11. 11. Debates: • Ethnocentric – All from one university • Usefulness – Can be applied to other environments
  12. 12. Loftus Weapon focus Theories of interviewing witnesses
  13. 13. Background: • Weapon focus refers to the concentration of a witnesses attention on a weapon which leads to them having difficulty recalling other details about the crime and identifying the offender. • Previous research has shown that people fixate their gaze for longer, faster and more often on unusual or informative objects.
  14. 14. Aim: • To provide support for the weapons focus effect when witnessing a crime.
  15. 15. Participants: • 36 students from the university of Washington. • Aged 18-31. • Half were recruited through advertisements and paid $3.50. • The other half were psychology students who participated for extra credit.
  16. 16. Procedure: • All participants were shown a series of 18 slides of events in a Taco Time restaurant. • For both groups, the slides were same except for one slide- the independent variable. • Control group: The second person in the queue hands the cashier a cheque. • Experimental group: The same person pulls a gun on the cashier. • The dependent variable was the recognition of that individual, measured by a 20 item, multiple choice questionnaire. • Participants were shown 12 pictures at random and asked to rate how confident they were of their identification on a scale of 1-6.
  17. 17. Results: • Answers to the questionnaire about the slideshow showed no significant difference between the control and the experimental groups. • In the control condition, 38.9% made a correct identification. • In the experimental condition, only 11.1% made a correct identification. • Eye fixation data showed an average fixation time of 3.72 seconds on the gun and 2.44 seconds on the cheque.
  18. 18. Conclusions: • The participants spent linger looking at the weapon and therefore found it harder to identify the offender from the line-up.
  19. 19. Issues: • Ecological validity – Not viewing a real event so little emotional attachment from the participants • Generalisability – All volunteers or students who are participating for something- money or extra credit. – Wanting to please the experimenter • Usefulness – How weapons can affect recognition • Control group present – Results not due to chance
  20. 20. Debates: • Individual vs Situational – What is present during an event can affect the ability to identify offenders • Ethnocentrism
  21. 21. Fisher and Geiselman The cognitive interview
  22. 22. Background: • The Cognitive interview is designed to take into account well known cognitive functions to avoid leading the witness. • The interviewer gives the witness a series of instructions to reinstate the context of the original event and to search through their memory using a variety of retrieval methods.
  23. 23. Background: • There are 4 main principles to the cognitive interview: – Interview similarity; memory of an event is enhanced when the psychological environment of the interview is similar to that of the original event- external- weather- emotional and cognitive features. – Focused retrieval; The interviewer is to generated focused concentration. There should be no interruption of the train of thought. – Extensive retrieval; Encouraged to make as many retrieval attempts as possible and encouraged to try a variety of angles. – Witness-compatible questioning; Successful retrieval reflects how compatible the questioning is with the witnesses unique mental representation.
  24. 24. Aim: • To test the cognitive interview in the field.
  25. 25. Participants: • 16 detectives from the Robbery Division of Dade County, Florida. • All experienced in the first phase of the experiment.
  26. 26. Procedure: • Detectives asked to record a selection of their next interviews using the standard techniques that they usually used. • This took 4 months and 88 interviews were recorded, mostly related to snatches or robberies. • Detectives then divided into two groups and one group was trained in the cognitive techniques- this was a group of 7 detectives, training was over four 60 minute sessions. • Interviews by both groups were then recorded over the next 7 months. • Interview recordings were analysed by a team at the University of California who were blind to the conditions.
  27. 27. Results: • Cognitive Interview detectives elicited 47% more information than before and 63% more information than the untrained detectives. • The time taken to interview witnesses was not significantly different, by Cognitive Interviews do take longer.
  28. 28. Conclusions: • Cognitive interview techniques work by helping detectives to gain more information.
  29. 29. Issues: • Generalisability – Only used 16 detectives from one area • Ecological validity – In their normal, working environment • Usefulness – Can help to train police to get more information from their witnesses. • Reliability – Data was analysed by another university – Single blind study • Ethics – Witnesses had to relive the events of the crime
  30. 30. Debates: • Ethnocentric – All detectives from Florida • Individual vs Situational – The amount of information witnesses give depends on the interview they have