Emotional decoding abilities in alcohol-dependence: A categorical perception study

Emotional and interpersonal difficulties have been widely described in alcohol-dependence [1] and are thought to play a crucial role in the development and maintenance of this disease [2]. In particular, impairments in the decoding of emotional facial expression (EFE) have been repeatedly reported and may have serious deleterious effects for the everyday life of alcohol-dependent individuals (ADI), notably by affecting their interpersonal relationships [3]. However, the large majority of earlier studies that assessed emotional decoding abilities among ADI were interested in the processing of prototypical full-blown EFE while in everyday social life, EFE are usually not entirely straightforward but are rather composed of a mix of different emotions [4]. The aim of this study was therefore to determine whether ADI exhibit the categorical perception effect, which is a critical process observed in healthy populations to efficiently decode ambiguous EFE. Nineteen recently detoxified ADI and 19 healthy controls (HC), matched for age and gender, were presented with facial stimuli depicting [4] EFE (happy, angry, sad, and neutral), morphed along continua between each possible pair of emotions. Participants had to indicate the predominant emotion within the randomly presented facial stimuli. For each EFE, a sigmoid function that estimated the percentage of identifications according to the morph steps was adjusted for each participant's data. While there was no significant group difference regarding the response slope (indicating how abruptly the shift in responses happens), the identification threshold (i.e. the function midpoint) was significantly increased in ADI compared to HC, independently of the EFE category. The categorical perception of EFE per se appeared thus preserved in alcohol-dependence, but ADI exhibited a bias in EFE decoding characterized by a global under-identification. To conclude, this study is the first to evidence an EFE processing deficit in ADI by using this kind of emotional continuum paradigm measuring the categorical perception effect.