The present set of experiments examined whether customs officers, police officers, and university students could detect children’s deception. When children received a direct interview, the correct identification rates of the customs officers, police officers, and students were near chance levels (Experiment 1). However, when children had engaged in moral discussions (Experiment 2) or been asked to promise to tell the truth (Experiment 3), all groups could accurately identify the lie-tellers and truth-tellers above chance levels. Experiment 4 replicated the major findings of Experiments 1–3 and ruled out the possibility that the adults’ accuracy in Experiments 2 and 3 was due to additional exposure to the children.
Signal detection theory analyses further confirmed that the three groups could discriminate between child lie-tellers and truth-tellers. Throughout most of the four experiments, adult participants did not display a response bias. When significant response biases were observed, they tended to be very small. Also, the biases observed in one experiment were not replicated in another experiment. With regard to discrimination ability (d′), discussing the moral implications of lying (Experiment 2) facilitated discrimination the most, followed by having children promise to tell the truth (Experiment 3). Increasing participants’ exposure to the children did not improve discrimination (Experiment 4).
The significant condition effects are worth noting. Deception was consistently most detectable when, prior to lying, children had considered the moral implications of deceit. During story-telling sessions, the majority of children indicated that the characters were lying, which was “very bad”. This moral discussion might have alerted children to the possibility that their own deceptive actions were equally negative. Whereas emphasizing the impropriety of lying may have affected children in the moral discussion interviews, emphasizing the importance of truth-telling (in the form of making a promise) may have had the same effect in the promise condition. We posited that each approach would increase children’s arousal during deception, accounting for why their lies were easier to detect.
Yet, recent analyses failed to support our hypotheses about the effects of arousal. Lie-tellers were no more aroused than truth-tellers. More surprisingly, the only effect of interview type revealed that children who had promised to tell the truth were believed to be less aroused than children who had engaged in a direct interview. There are several explanations for our failure to find the expected arousal effects. First, it is possible that it is difficult to accurately assess arousal through observation alone. Second, the arousal related to deception may be as subtle as that resulting from cognitive dissonance. In that case, arousal did occur, but it was not readily detectable by physiological measures (i.e., it was only revealed through attributions) (e.g., Zanna & Cooper, 1974
). Third, the interview manipulations may have increased arousal. However, children may simply have been actively suppressing it to a greater extent in the moral discussion and promise clips. In turn, this increase in cognitive effort may have led to the expression, or leakage, of the deception elsewhere. Finally, it is possible that our hypotheses are simply incorrect and that changes in arousal are not responsible for corresponding increases in lie detection. Of course, all of these alternatives are merely speculation and should be thoroughly tested in future studies.
It should be noted that, although participants’ accuracy was above chance in some conditions, their overall ability to detect children’s lies was poor. In the best displays of lie-detection accuracy (i.e., when rating moral discussion clips), adults classified less than 70% of the children correctly; over 30% of the children were labeled incorrectly. In fact, the average accurate identification rate across conditions and groups was just slightly above the 50% chance level. These findings are similar to those reported in other studies of adults’ deception (e.g., Ekman et al., 1999
). This level of accuracy, although significantly different from chance, is not clinically or naturalistically meaningful. Most members of the justice system would surely be uncomfortable with such a low level of predictive success. Although there were not enough children who correctly (and incorrectly) admitted to having committed the transgression to perform full lie-detection analyses, consideration of the issue revealed that participants believed approximately 90% of confessors. Any firm conclusions about participants’ willingness to believe truthful versus false confessions are beyond the scope of this paper, but the lack of perfect accuracy suggests that this issue should be explored further. Overall, the findings related to the study of adult deception may be generalizable to examinations of child lie-tellers.
As in previous studies with adult deceivers (e.g., Kraut & Poe, 1980
; Porter, Woodworth, & Birt, 2000
), there were few differences between the performance of our experienced and untrained groups. Overall, students performed as well as customs officers and, in one case, both of these groups were more accurate than police officers. Thus, experience and training did not appear to affect the successful identification of deception. However, it may be unrealistic to expect law enforcement officials to perform better than untrained adults. Officers rarely receive feedback about their accuracy (DePaulo & Pfeifer, 1986
). Arrests and convictions are not necessarily indicative of guilt. Moreover, officials can never truly establish a base rate because they rarely know whether people they have not interviewed (or whom they have spoken to and let free) were lying. As a result, it is difficult for them to learn from encounters and adjust the criteria they use to detect deceit. Given this uncertainty, officers may acquire experience with lie detection without improving their skills. Furthermore, because lie detection is seen as an important skill in law enforcement, pressure to improve in the absence of feedback may encourage superstitious behavior (e.g., illusory correlations between behavior and perceived truthfulness). Such cues could distract officers from useful information that may permit improved performance. Thus, it is not surprising that officials do not perform better than laypersons. It is interesting to note that experience with children also does not improve adults’ detection of children’s lies. About half of the officers had children of their own. However, their lie-detection accuracy did not differ from those officers who did not have children. This result is consistent with Talwar and Lee’s (2002)
finding that parents could not detect children’s lies.
Previous research has shown that law enforcement officials tend to be more confident than untrained observers even though confidence and accuracy are often unrelated (e.g., DePaulo & Pfeifer, 1986
; DePaulo et al., 1997
). The present findings are highly consistent with this conclusion. Daily work experience may be one reason for the group differences in certainty ratings. The customs officers were trained to detect deception with minimal information, which might have made them more comfortable with the present task. As a result, they were more certain about their decisions. On the other hand, the police officers were more accustomed to lengthy investigations and extensive information gathering. Similar to students, who had no training or experience, they may have been unfamiliar with the task demands (e.g., rapid decision-making with limited information) and more uncertain about their decisions.
To the best of our knowledge, the present study is the first in the literature that has systematically examined law enforcement officials’ ability to detect children’s lies. However, there are several limitations of the studies and further empirical research is urgently needed. The first issue is the generalizability of the results. In the present experiments, participants were asked to detect children’s lies about peeking at a toy. There are certain benefits and disadvantages of this approach. Unlike previous studies, the present procedure allows children to lie out of their own volition and provides realistic samples of deception. One weakness is the less-than-serious nature of the lie produced. Law enforcement officers are rarely asked to judge such minor transgressions. The majority of children who enter the justice system are interviewed about serious matters (e.g., child abuse). Thus, procedures (e.g., having children promise to tell the truth) must be examined in more legally relevant contexts in which children face as severe consequences as they would encounter in real life situations. Of course, ethical issues must be taken into account when designing such studies.
The second issue concerns the amount of information provided to the adult participants in the present experiments. In real life situations, law enforcement officials usually conduct their own interviews. Not only can they view reactions first-hand (rather than on videotape), but they can ask their own questions and follow-up on any inconsistencies. Direct encounters with children may enhance law enforcement officials’ accuracy at detecting children lies. One reviewer suggested that the groups under investigation likely experienced different rates of lying and truth-telling in the real world (e.g., police officers might be exposed to more lie-tellers than university students). In turn, base rate expectancies provided in the instructions (e.g., that approximately half of the children presented would be lying), which were meant to reassure participants that they were not being tricked, might have artificially altered the groups’ performance. Although there is no proof that the inclusion of base rates in the instructions actually impacted accuracy, other evidence suggests that it had little effect. First, providing base rates is typical of other studies of lie detection (e.g., Frank & Ekman, 1997
). Second, due to the base rate fallacy, there was no real reason to expect that participants would actively use, or be sensitive to, the base rates. Perhaps if the purpose of the experiments were to determine the base rate expectancies of each group (and the resulting effect on accuracy), the instructions would have been flawed. Instead, the base rate information was needed to allow for a fair comparison, in terms of performance, across groups. There is no reason to think that base rate distortions are limited to groups (i.e., members within groups may hold dramatically divergent beliefs about the rate of lie-telling and truth-telling in the world). If participants were left to use their personal base rate expectancies, performance could have been distorted due to different expectations. This possibility remains to be examined in future studies. Finally, signal detection analysis is specifically designed to provide a measure of detection accuracy that is independent of response bias (base rate expectations). The d′
values reported reflect the ability to discriminate between truthful and untruthful responses, independent of the individuals’ beliefs about the overall likelihood of lying.
The third limitation is that it is not clear whether children revealed any markers of deception and whether adults consistently use these cues when making their decisions. Future studies are needed to examine children’s nonverbal behavior during deception. For example, the child lie-tellers and truth-tellers in the present experiments could be compared in terms of their facial expressions and body movements. It is possible that participants’ chance performance was partially influenced by outliers (i.e., children who were very easy and difficult to classify). Although no child was accurately identified (as a lie- or truth-teller) 100% of the time, further analyses could examine the variability, in terms of lie-telling ability, across children. Also, the adult participants could be asked about the cues they relied upon when making their decisions. Another set of studies arising from this issue could investigate whether lie-detection ability is stable. It may not be surprising that participants performed at chance if they were actually guessing. Measuring accuracy over time (both within and across sessions) could indicate whether performance is due to random fluctuations (e.g., luck) or enduring ability. Thus, analyses of the children’s nonverbal behavior and adults’ test–retest reliability at detecting children’s deception would clarify whether adults’ performance in the present set of experiments was due to their inability to detect deception at all or the ability of some children to lie effectively.
Despite the limitations of the present experiments, the findings have important implications for the legal system. Law enforcement officials’ poor performance in the present experiments may debunk a common belief that children are unable to effectively deceive adults. Frontline workers should be made aware of these findings so that children’s lie-telling skills are not underestimated. Our results indicate that interviewers must exercise caution when dealing with young witnesses, gathering concrete evidence rather than relying on instincts. Our findings speak to the danger of becoming overly confident about one’s ability to detect children’s lies simply because one has extensive experience with children or one’s job calls for the determination of truth.
The condition effect is instructive for legal professionals who seek to construct interview procedures that more effectively elicit truthful testimony from children. When children testify in most North American courts, they must undergo a “competence examination.” In this examination, children are asked to discuss the moral implications of lying and tend to be asked to take an oath or to promise to tell the truth. Talwar et al. (2002)
have recommended that interviewers only ask children to promise to tell the truth. They proposed that “correctly” answering questions about lying and truth-telling should not be a precondition of children testifying. These suggestions were based on their findings that only having children promise to tell the truth decreased the incidence of lying; moral discussion did not change the rate of deception. However, the present research suggests that, although moral discussion does not increase the likelihood of truth-telling, the inclusion of moral reasoning tasks consistently facilitates the detection of children’s lies. Given the relatively short amount of time needed for moral discussion, the possible benefits in terms of increased lie-detection accuracy seem to justify its continued inclusion in forensic interviews and court. Because having children promise to tell the truth appears to decrease lie production and increase lie detection, both practices (i.e., having children promise to tell the truth and moral discussions about truth and lie-telling) should be incorporated into child witness interview procedures.