Antisocial behavior is described as individual behavior lacking consideration for others, no matter whether intentional or through negligence 
. Clinical manifestations of antisocial behavior are subsumed under the concept of antisocial personality disorder of the DSM-IV classification 
, and the corresponding diagnosis of dissocial personality disorder of the ICD-10 
. Both diagnostic manuals agree on disorder characteristics such as lack of respect for social norms, irresponsibility, reckless and irritable aggressive behavior, and lack of remorse or guilt 
. In favor of a dimensional theoretical account of personality, non-clinical manifestations of antisocial personality disorder characteristics can also be observed in healthy and non-criminal community samples 
. Recent theoretical accounts of antisocial behavior stress biological, developmental, and social risk factors 
for developing antisocial personality disorder.
These behavioral peculiarities of antisocials in social situations give rise to the question whether basic processing of social cues is impaired in these individuals. In every-day life, human faces and facial expressions are regarded as valuable social cues 
, because they embody crucial information useful in social exchange situations. Efficient face analysis can be linked to evolutionary aspects of perception, interaction, and communication in social life 
. In line with this assumption, Marsh and Blair 
summarized that antisocial populations repeatedly show deficits in recognizing emotional displays in faces, in particular fearful expressions, assessed in behavioral or neuroimaging settings.
Consequently, the question arises whether impaired recognition of facial expressions in antisocials may be due to deficits in basic sensory functions such as visual processing or deficits in cognitive functions such as attention. However, no study has addressed this particular research question in healthy individuals with antisocial tendencies so far. Although attention deficits have been reported in individuals suffering from antisocial personality disorder 
, one has to keep in mind that these individuals might have also suffered from psychopathy. Psychopathy can be regarded as personality construct sharing some conceptual overlap with antisocial personality disorder 
. A comorbidity of around 30% has been reported for psychopathy and antisocial personality disorder 
. However, psychopathy focuses on antisocial personality traits mainly reflected in affective-interpersonal deficits whereas antisocial personality disorder emphasizes observable antisocial behavioral tendencies. Thus, the comparability between these two concepts is somewhat limited. Antisocial personality disorder is most likely associated with impulsive-aggressive tendencies of secondary psychopathy. Secondary psychopathy refers to the facet of psychopathy characterized by increased impulsivity and a socially deviant life style 
. Nevertheless, antisocial traits are also associated with deficits in emotional reactivity and as such reflected in overall diminished skin conductance variability 
or in recognition deficits of fearful facial expressions 
. Furthermore, inadequate sensitivity to emotional stimuli and stress reactivity has been observed in antisocial-impulsive aspects of psychopathy 
. Recently, Verona, Sprague, and Sadeh 
conducted a direct comparison between psychopathic individuals and individuals suffering from antisocial personality disorder. The authors found psychopathy to be associated with reduced neural processing of negative emotional stimuli, whereas antisocial individuals were associated with prioritized processing of these negative stimuli under inhibitory control requirements.
To determine possible impaired stimulus processing stages, empirical evidence of the precise temporal occurrence of these deficits is necessary. Electrophysiological measures are a useful tool to investigate the time course of face processing. The present study focused on two event-related potentials (ERPs) that have been linked to face processing; the P1 and the N170, respectively. Furthermore, the P300 component was of interest because of its assumed role in attentional processes 
The P1 is a positive-going ERP which can be found at parieto-occipital and occipital electrode sites with onset latencies between 60 and 80 ms and peak latencies between 100 and 130 ms after visual presentation 
. The P1 indexes an early stage of visual processing. Physical stimulus characteristics such as luminance or contrast (i.e., low-level visual features) are reflected in the P1 amplitudes 
. Indeed, neuronal generators of the P1 component were found within lateral extrastriate areas 
. However, apart from low-level visual processing, P1 amplitude is also modulated by top-town attentional processes. Its amplitude is reported to be enhanced for attended compared to unattended stimuli, which holds true in particular in paradigms investigating spatial attention 
. Moreover, P1 has also been linked to face categorization processes 
. For example, negative emotional faces have been observed to evoke larger P1 components than positive emotional faces 
The P1 is usually followed by the N170, an ERP component that has also been linked to early face processing stages 
. The N170 is a negative-going deflection of the ERP peaking about 130 to 190 ms after stimulus presentation at occipito-temporal electrode sites. Neuronal generators of the N170 are assumed to lie within ventral visual areas (i.e., fusiform gyrus) 
or within lateral temporal regions 
. The N170 is reported to be enhanced after facial compared to non-facial stimuli 
. Eimer 
related the N170 to structural encoding of facial features, thus responding to faces on a categorical rather than on an individual level 
. To be more specific, the N170 is sensitive to the presentation of faces in general, but it does not incorporate information about whether a particular face is familiar or not. It remains a question of debate whether the N170 is also sensitive to emotional facial expressions. For example, Batty and Taylor 
reported enhanced N170 amplitudes after fearful compared to neutral faces as well as shorter N170 peak latencies for positive compared to negative emotional expressions. In contrast, Eimer and Holmes 
concluded that the N170 amplitude was not at all sensitive to different facial emotional expressions.
The P300 (also P3 or classical P3b) is an ERP deflection at posterior electrode locations, peaking around 300–600 ms after stimulus presentation 
. P300 amplitude variation depends on factors such as categorical stimulus probability 
, stimulus quality, attention 
, as well as task complexity, resource allocation 
and arousal states 
. Findings concerning P300 amplitude variation in antisocials and psychopaths are inconsistent; both amplitude enhancement 
as well as decrease 
have been reported.
The present study aimed to investigate early processing stages of facial stimuli in individuals high and low on antisocial traits from a sub-clinical sample in a gambling task context. We chose to administer a gambling task instead of a classical passive viewing task to enhance the salience of the presented faces which served as feedback stimuli. Initially, this task was administered to investigate expected and unexpected feedback outcomes 
. Behavioral task measures such as reaction times and button choice behavior were assumed to reflect task engagement. The presented feedback faces always incorporated information regarding correctness of a prior response. Furthermore, we chose happy and angry faces representing feedback since the distance between two facial emotional expressions is reported to be maximal from anger to happiness 
. Notably, no emotion recognition deficits have been reported in antisocial populations concerning anger and happiness displays 
. Thus, we assumed that participants could easily differentiate between positive and negative feedback.
In accordance with possible attention deficits in antisocial personality disorder 
, we explored whether any deficits in early sensory analysis were observable in healthy individuals scoring high on an antisocial trait measure. If so, we expected the high-trait group to display diminished P1 and N170 components compared to the low-trait group. Regarding stimulus valence, i.e., facial expression, we expected larger P1 amplitudes after negative than positive feedback faces 
, but no modulation of N170 amplitudes 
. Since Marsh and Blair 
reported no emotion recognition deficits for anger and happiness in antisocial populations, we did not expect any interaction effects between feedback valence and antisocial traits. Additionally, we explored behavioral task outcomes such as reaction times and button choice behavior.