The interrogation process is one that, over the years, has evolved from a simple question/ answer process, into a prosecutorial weapon geared around police persuasion and heavy handed tactics. In fact, modern police interrogations are so powerful that they have been known to elicit false confessions from innocent people. Justifying their aggressive approach , these law enforcement professionals claim to be able to determine a person’s guilt or innocence solely on a pre-interrogation interview in which they observe the suspect’s verbal and nonverbal behavior.

Research, however, has failed to support the claim that individuals are capable of attaining high levels of performance in detecting truth or deception. In fact, it has shown that individuals perform at no better than chance level in detecting deception, that training programs produce only inconsistent improvements in ability, and that police investigators and others with relevant training perform only slightly better, if at all. Thus, there is no hard evidence to support the claim that the use of verbal and nonverbal behavior can accurately predict deception. In fact, reliance on the use of verbal and nonverbal behavior may result in unjustified accusations, as well as forced confessions.

Although it is possible that training or experience may increase an individual’s ability to discriminate between truthful and deceptive target persons, it may alternatively bias decisions toward truth or deceit on the basis of a variety of factors. The signal detection theory (SDT) provides a framework for separating performance into two different parameters, namely discrimination accuracy- the ability of an individual to correctly detect a signal (deception) versus correctly reject its absence (truth), and response bias- the degree of evidence necessary for an individual to respond that a signal (deception) has been presented. With regards to training or experience, it seems that certain manipulations would only influence discrimination accuracy by enhancing one’s ability to correctly differentiate truth from deceit. It may also be assumed that training and experience would bare no influence on the response bias parameter (the tendency to overly respond “truth” versus “deceit”).

Analysis of Previous Research:

Meissner and Kassin began by a brief reanalysis of previous research. They focused on research that examined the influence of either experience or training in the detection of deception. They focused only on research that (a) reported accuracy for both truthful and deceitful targets and (b) included a no training/experience control group. Overall, they found six studies that could fit their criteria. An SDT analysis was conducted on the performance means that were either recorded in the paper or reported by the authors. Estimates of hits and false alarms were used to compute SDT estimates of both discrimination accuracy and response bias. Finally, the difference in performance between the experimental and control groups were compared.

They found that across studies, both training and prior experience engendered a more liberal response criterion (a tendency to respond “deceitful”) when compared to participants in the no-training/ experience control conditions. Contrary to expectations, however, training and experience had no effect on participants’ ability to accurately discriminate truth from deceit.

Meissner and Kassin’s effect size analysis of previous research led to the finding of a investigator bias effect, meaning that training or prior experience may lead towards a bias of “deceit” judgments. This is of concern because if investigators are truly biased toward deception, then pre-interrogation interviews might prompt more pressure-filled interrogation, further resulting in false confessions.

To further explore the investigator bias effect, Meissner and Kassin set out to extend on the previous research of Kassin and Fong. Kassin and Fong (1999) experimentally trained some student participants, but not others, in the detection of truth and deceit, before obtaining judgments of mock suspects. Their results indicated that although training did not increase overall detection accuracy, it did increase the confidence that trained students had in their judgments, as well as the number of reasons they cited for their judgments. Meissner and Kassin added a group of law enforcement investigators in order to compare them with Kassin and Fong’s trained and naïve students and to examine the correlations between experience, training and various indices of performance.

Methods:

The process was the same as used in Kassin and Fong’s but with an additional 44 law enforcement investigators. Eight guilty suspects committed one of four mock crimes, and eight innocent suspects were instructed to appear at the scenes of these crimes. All suspects were interrogated by the same detective, who was intimidating in his demeanor. Each investigator would watch one of two tapes, both with eight male suspects, four of which were innocent and four of which were guilty. Each was asked to determine guilt or innocence, rate their confidence, and site their reasons.

Results:

As in previous studies, overall accuracy for the investigators and students did not significantly differ. Planned comparisons also showed that both naïve and trained students were significantly less confident than police investigators. Interestingly the was no correlation between judgment accuracy and confidence across investigators. It also showed that both naïve and trained students produced more reasons than did police investigators.

Signal Detection Analysis showed that trained students produced fewer hits relative to police investigators, Naïve students, however, produced fewer false alarms than investigators. And when students were combined, results indicated that investigators generated significantly more hits and more false alarms. These results were found to be consistent with their study wise analysis revealing no significant difference in discrimination accuracy, but there was an observable effect of response bias.

A correlational analysis showed that prior experience in law enforcement was not related to judgment accuracy, decision confidence, or number or reasons cited for judgments. Prior training did, however, increase the number of false alarms, and a bias to see deceit.

Discussion:

The goal of this research was to better understand the influence of training and experience on deception-detection judgments. By applying the Signal Detection Theory, they were able to distinguish between two different parameters of detection: discrimination accuracy and response bias. Their original hypothesis was that training and experience would enhance one’s discrimination accuracy, and bare no effect on response bias. Contrary to expectations, however, training and experienced seemed to loosen response criterion allowing for greater response bias. And across studies, training produced no reliable effects on the ability to discriminate between truth and deceit. All in all, the investigators failed to outperform the subjects of Kassin and Fong’s original study. In fact they displaced a liberal response bias and claimed greater confidence.