Exam 3: Section 1: Lie Detection

Correct Answer:

Verified

Main points:
• fMRI is expensive and not portable;
• it requires the subject to lie motionless inside a machine and keep silent (push buttons for answers);
• fMRI only takes brain pictures every 2 seconds, which is too slow compared with the speed at which the brain works;
• there is wide variation among people in terms of the areas of the brain that are activated by lies, which makes it difficult to determine precisely whether a particular person is lying or telling the truth.

Correct Answer:

Verified

Main points:
• The RIT and CQT are based on comparing physiological responses with crime-related questions and responses (a) to other (irrelevant) questions in case of RIT and (b) to uncomfortable but not crime-related questions in case of CQT.
• The GKT takes a different approach and compares reactions of the suspect with information that only the person who committed the crime would know. This approach takes much less skill on the part of the polygrapher than does RIT and CQT but more skill on the part of the investigator in formulating the questions.
• GKT also makes it less likely to produce false positives though it is still just as susceptible to interference from countermeasures.

Correct Answer:

Verified

Main points:
• Most studies assessing the validity of the polygraph in terms of its lie-detection ability are controlled (lab) studies using mock crimes.
• The stakes are much lower in lab studies, the lies are much simpler, and the "suspects" have little exposure to training in countermeasures that real suspects might be motivated to obtain.
• This makes it very difficult to generalize the results reasonably to actual criminal cases and makes it likely that the accuracy of polygraph as assessed in lab studies is somewhat inflated. Even then, the rates of accuracy do not even approach 80%.