Mann, Vrij & Bull

1. investigate the lying & truth telling behaviours of suspects in high stake situations (generates real lies & truths)

1. Type of Sampling
   1. opportunity sampling
2. 16 police suspects
3. 13 Males, 3 Females (4 Juveniles. {one 15 yr old, three 13 yr olds]
4. 15 Caucasian, 1 Asian

1. IV(s)
   1. 8 Coded Behaviours

      Annotations:

      • >  Gaze Aversion (number of times suspect looks away from interviewer) >  Eye Blinks (frequency of blinks) >  Head Movements (frequency of head movements, up & down, side to side) >  Illustrators (frequency of arm/hand gestures while talking) >  Self-Manipulators (frequency of scratching neck/wrist) >  Hand/Finger Movements (frequency of moving the hand and fingers without moving the arm) >  Speech Disturbances (Frequency of saying things like "ahh", "umm", unfinished sentences, repetition of words/sentences, stuttering, sentence changes. >  Pauses (duration of noticeable pauses)
2. DV(s)
   1. Lying/Truth telling behaviours

1. Natural Experiment (Quasi)

Annotations:

• > Increase in Gaze Aversion > Decrease in Hand/Arm Movements > Increase in 

1. indicators of lying are an increase in pauses and a decrease in blinking.

1. Strengths
   1. If participants are unaware that they are being observed, they are more likely to behave naturally which makes the findings valid.

      Annotations:

      • The suspects were unaware that the recordings would be analysed for lying/truth telling behaviours. They were more likely to be showing natural behaviour. This makes the findings more valid.
   2. High Ecological Validity
2. Weaknesses
   1. If participants are unaware that they are being observed, the study goes again ethical guidelines, including informed consent & deception

      Annotations:

      • Suspects were unaware that the recordings would be analysed and they were not asked for informed consent to be used in the study. They were deceived. Therefore the study goes against ethical guidelines.
   2. Situational variables are difficult to replicate, therefore it is difficult to know whether it is IV directly affecting DV or an uncontrolled situational variable.
   3. Less Control
   4. Not Generalisable

1. Informed Consent
2. Deception
3. Debriefing