Mann Flashcards
Mann Procedure
Field experiment.
Officers questionnaire about experience of detecting liars.
54 video clips of 14 suspects. Easy to spot expressions and movements. There was separate evidence established about whether they were telling the truth or not.
DV Mann
- Was the suspect lying or not
- Confidence on decision
- Cues that made them reach this decision
Mann Findings
1: Officers spotted lies 66% of the time, identified truthful statements 64% of the time.
- HIGHER THAN CHANCE.
- Positive correlation between two scores, hence people who were better at spotting lies were also better at identifying truthful statements.
2: Positive correlation between how many years of experience the 99 Kent police officers had at interviewing suspects and their score for detecting lies. (However no control therefore cannot prove this is the reason.) (Experience data gathered from self report - questionnaire about their experience detecting liars.)
3: Most frequently cited cue = gaze and eye contact. (However, this is not supported by research as a valid cue).
Second = body movement and gestures. Also pointed out inconsistency in stories and fidgeting, however the best lie detectors cited story cues eg. faulty details and inconsistencies.
Mann
High Eco V - field experiment using 99 real Kent police officers at footage of real suspects.
Valid - other supporting evidence establishing whether they were telling the truth.
Ethical - confidentiality of suspects interview maintained.
Not representative eg. for large inner city police forces.
No control, therefore no comparison to members of the public capabilities to detect lies.
Mann Conclusions
1: Gaze no vaid cue
2: Relying on police manuals, and hence suggest cues may not be relevant.
3: Good lie detection may depend more on story cues.
4: Lie detection occurred at a level better than chance.
Intro
Purpose of interview is to identify guilt or innocence.
Police believe they are able to detect liars through minor body language cues eg. avoiding eye contact, fidgeting, touching face. Also through inconsistencies in story with repeated questioning.
Ethical issue of videotapes of suspects being interviewed being too sensitive for general public. Hence they are unable to watch this. This is due to the suspect being innocent until proven guilty and the suspects right to privacy until the case in taken to court.
Mann also noticed the police officers had many faulty ideas of deception cues, these may have been picked up from police manuals, traditional practices and even TV shows.
