In recent years, increasing attention has been focused on the high rate of delinquency, which is a serious social problem in some countries 1. To address this problem, it is important to clarify the psychological mechanisms underlying conduct problems in youths. Some clinical observations and questionnaire surveys have revealed deficits in emotional communication among children and adolescents with conduct problems (e.g., 2).

One crucial component of emotional communication is the recognition of emotional facial expressions of other individuals. Facial expressions indicate moment-to-moment changes in inner emotional states 3 and/or communicative intentions 4. People often use the information communicated by emotional facial expressions as cues for modulating social behaviors 5. In particular, the recognition of others' facial expressions has been shown to modulate aggressive behaviors 6. This finding suggests that there may be a relationship between facial expression recognition and conduct problems involving aggression.

Consistent with this notion, some previous studies have revealed that delinquents are impaired in their recognition of facial expressions of emotion 789. However, the types of emotion they have difficulty recognizing have not been clearly identified. For example, McCown et al. 9 investigated the recognition of facial expressions of six basic emotions (anger, disgust, fear, happiness, sadness, and surprise; cf. 3) among incarcerated juvenile delinquents. They found that, compared with control youths, juvenile delinquents were less accurate in the recognition of facial expressions of disgust, sadness, and surprise. On the other hand, Cadesky et al. 7 investigated the recognition of facial and vocal expressions of anger, fear, happiness, and sadness in children with conduct problems. They reported that these children were impaired in the recognition of fear, happiness, and sadness. In summary, although the previous studies have consistently indicated the impairment of facial expression recognition in delinquents, it remains unclear whether there is a specific pattern of impairment.

Cadesky et al. 7, in their subsequent analysis, examined the error patterns that suggested poor emotion recognition among delinquent participants. By conducting visual inspections of their data, they found that participants with conduct problems tended to mislabel other emotions as anger. Because they did not conduct statistical analyses, their conclusion should be regarded as tentative. This finding, however, seems to provide an important clue regarding how delinquents misperceive others' emotional expressions. Several researchers have reported a similar tendency among children with conduct problems to misperceive benign social situations as hostile 101112.

In the present study, we investigated facial expression recognition in adolescent/young adult delinquents in greater detail than have previous studies, comparing delinquents with age- and gender-matched controls. We examined participants' recognition of facial expressions conveying the six basic emotions previously examined by McCown et al. 9 and conducted error analyses for each emotion. We predicted that delinquents would recognize facial expressions of some emotions less accurately than would control participants, with a bias toward the misinterpretation of emotions as anger. Given that some previous studies have reported cultural differences in expression recognition (e.g., 13), we used facial-expression stimuli from two different cultures.

Our results revealed that adolescent/young adult delinquent participants were less accurate in recognizing facial expressions of disgust than were control participants. The problems in the facial expression recognition among delinquents are consistent with findings of previous studies 789. More specifically, the present results are consistent with a previous study in identifying impairment in the recognition of disgust 9. Despite methodological differences among studies, such as differences in the cultural background of participants, the present study is compatible with previous studies in suggesting that delinquents have impaired ability to recognize emotional facial expressions.

Our results on errors revealed that delinquents had a tendency to misrecognize facial expressions of disgust as anger. Although this type of error was also prominent in control participants, which is plausible because angry and disgusted facial expressions are similar with respect to featural changes and both express negative emotional states 3, delinquents showed a much greater tendency than did control participants to exhibit this misrecognition. Although the difference in error rates between groups was not large (17.2%), such errors can provide valuable information regarding impairments in expression recognition (e.g., 19). This error pattern is consistent with the suggestion by Cadesky et al. 7 that children with conduct problems tend to perceive other emotions as anger. The present results also agree with previous reports that participants with conduct problems misperceived social situations as hostile 101112, although those studies did not focus on the recognition of facial expressions. Extending these previous findings, the present study provides the first clear evidence that delinquents have a bias toward the misrecognition of others' disgusted expressions as anger.

Delinquents' misperception of facial expressions of disgust as anger is important when we consider the social functions of these emotions. Although both angry and disgusted facial expressions induce negative emotional states in perceivers, angry expressions induce higher arousal than do disgusted expressions 22. Furthermore, disgusted facial expressions suggest withdrawal motivation on the part of the sender, whereas angry expressions indicate approach motivation 23. Specifically, angry facial expressions imply the occurrence of subsequent hostile behaviors 24. These data suggest that the misrecognition of disgusted facial expressions as angry expressions might induce relatively more intense emotionally aroused states in the receiver, and might result in anticipation of relatively more dangerous behavior on the part of the sender than would accurate recognition. These misperceptions of facial expressions might therefore contribute to aggressive behaviors in delinquents.

The bias toward misrecognizing other emotions as anger is particularly significant because anger appears to play an important role in delinquency. It has been pointed out that children with conduct problems are quicker to become angry and their anger tends to be more intense 25. Plattner et al. 26 confirmed that delinquents experienced higher state and trait negative emotions, including anger, than did control participants. A previous self-report study also found that anger was the reason most often given for interpersonal delinquency 27. In addition, some previous studies reported that the perceivers' own emotional states influenced the recognition of others' emotional facial expressions (e.g., 28). Taken together, the data suggest that delinquents might be projecting their own heightened angry emotions onto others when they misperceive others' negative, but not hostile, emotional states as anger.

Promising directions for further investigation include efforts to understand the developmental mechanisms for the impaired recognition of facial expressions in delinquents. One possible mechanism suggested by some studies involves a link between child maltreatment and subsequent delinquency 2930. Interestingly, consistent with our finding, Pollak et al. 31 found that maltreated children demonstrated impaired recognition of facial expressions of disgust, along with a misrecognition bias toward anger. Also, in keeping with previous findings for delinquents 101112, studies have shown that maltreated children exhibited a bias toward attributing hostile intent to others 3233. The parallel between findings from these earlier studies and results of the present study suggest that impaired facial expression recognition in delinquents may be, at least in part, attributable to experiences of abuse during childhood.

Our results revealed differences in recognition accuracy in response to Caucasian and Japanese faces selected from standard stimulus sets 1718. This result suggests the possibility that cultural differences underpinned the finding that facial expressions depicting disgust were accurately recognized more frequently in response to Caucasian rather than Japanese models among both Japanese delinquent and control participants. However, we must note that the stimuli differed not only with regard to cultural dimensions but also with regard to some other properties. For example, whereas Caucasian stimuli included both young and middle-aged models, Japanese stimuli consisted solely of young models. Future studies might be necessary to confirm the cultural differences in expression recognition among delinquents.

Some potential limitations in the present study must be acknowledged. First, the mean IQ of the delinquents in this study was near the bottom of the normal range, raising the possibility that these delinquents showed impaired expression recognition partly because the task was too difficult for them. However, the MANCOVA revealed no significant influence of IQ on group differences. Furthermore, there was no significant group difference with respect to the recognition of fear, which is generally the most difficult to correctly recognize among emotions (cf., 34). Consistent with this finding, previous studies investigating expression recognition in individuals with subnormal intelligence did not find specific impairment in the recognition of facial expressions of disgust or a misrecognition bias toward angry expressions 35. These findings indicate that the impaired expression recognition in delinquents found in this study was attributable to a bias that was independent of intelligence level.

Second, the reaction times of responses were not recorded and analyzed in the present study. It is possible that different recognition performances derived from different cognitive processes, which could have been reflected in reaction times. Studies investigating reaction times will provide clues regarding the cognitive processes underlying expression recognition in delinquents.

Finally, confounding factors might have contributed to differences in expression recognition. For example, previous studies have shown that psychiatric disorders (e.g., schizophrenia 36) and socio-economic status (e.g., economic disadvantages 37) can influence expression recognition. In this study we were not able to access information on these issues due to the policies of the ministry that administrates the facilities. Furthermore, other studies have shown that the emotional states (e.g., state anxiety 28) and personality traits (e.g., empathy 38) of participants can affect expression recognition. These factors might have also influenced expression recognition in delinquents. Future research incorporating these factors should provide additional insights regarding expression recognition in delinquents.

In summary, we found that the adolescent/young adult delinquents were impaired in their recognition of facial expressions of disgust. Their error patterns showed that they had a tendency to misrecognize facial expressions depicting disgust as anger. These results suggest that one factor underlying delinquency might be impairment in understanding emotions communicated by disgusted facial expressions, especially a tendency toward hostile interpretations.

The authors declare that they have no competing interests.

WS, NM, and MT designed this research. WS, SU, and NM collected the data. WS and SU analyzed data. WS, SU, and MT wrote the manuscript. All authors read and approved the final manuscript.