HCI - Lecture 18: Application: Facial Composite Technology Part 1 Facial Composites Help the police identify criminals based on a witness' description Unfamiliar -> wait (3-4hours) -> enhanced cognitive interview -> police officer (researcher) -> face composite -> Familiar 'Enhanced' Cognitive Interview Set of techniques to help a person recall the face as completely and accurately ad possible; used with co-operative eyewitnesses (Geiselman & Fisher, 1987) · Rapport building · Context reinstatement · Free recall · Using their own words; own time · Report everything; no guessing · Interviewer doesn't interrupt · Repeated free recall · Cued recall What Might be Going Wrong? . Investigating the different areas of the face Example I: participants named 30 famous faces, half external and half internal features; control group named complete faces Example II: unfamiliar faces; internal facial features are valuable for familiar face perception, but internal and external features are equally important when the face is unfamiliar Witnesses can have difficulty in constructing the part of a face that is important for recognition by another person How Could Naming of Composites be Improved? · Make use of information from different observers . Multiple witnesses to a crime Morphing: · Combines memories from different people into a single 'morphed' image . The police can publish a morphed image in the newspapers and on TV; rather than individual composites · Laboratory research suggests that morphed composites are effective for naming of the relevant target However, approx. 70% of witnesses cannot recall the face in detail and so a traditional composite tends not to be constructed in the first place
Better Ways to Build a Face What's wrong with the normal way to build a face? We are: · Not very good at describing faces · Not very good at selecting eyes, brows, noses, mouths, etc. . Worse at doing these the longer we wait . Only good at recognising a face when seen more than once or familiar Example: 'How useful is EvoFIT?' - Asked people to make composites of snooker players - Looked at a picture, waited 2 days, described the face, made a composite - EvoFIT and PRO-fit (control) - Snooker fans attempted to name the composites EvoFITs Constructed in Police Investigations Methodology: . Police were trained to use EvoFIT · Used system for a set period of time · DV was number of times a person was arrested/convicted after an EvoFIT was made · Formal trials by five police forces: o Lancashire o Derbyshire o Devon & Cornwall o Romania o Humberside# Part 2 Why is EvoFIT superior to other composite systems? · Feature-based systems, e.g. E-FIT, ProFIT, FACES · Holistic system fi EvoFIT Problems with Facial Descriptions · Verbal descriptions are usually feature based, creating a "verbal overshadowing effect" · Holistic/configural information is more important in face recognition Techniques for creating more recognisable composites · Constructing internal features first . Adding the external features (e.g. hair, clothing) at the end · Post-production techniques o Perceptual stretch o Feature occlusion o