I err, therefore I am: Neural signature of error-monitoring predicts self-awareness in infants

Self-reflection is central to human cognition and arguably a defining feature of human consciousness, yet the mechanisms enabling our mind to reflect upon itself and to construct a sense of self are unclear. Specifically, whether metacognition implies self-awareness, is independent of it, or emerges because of it, remains a subject of debate, fuelled by reports of metacognitive-like behaviour in preverbal infants and non-human animals. Building on evidence that 12-month-old infants show neural signatures of internal error-monitoring, we follow infants longitudinally from 12 to 18 months, when infants first start exhibiting evidence of a conceptual self-representation. Using a gaze-contingent match-to-sample paradigm with concurrent eye-tracking and EEG, we confirm that infants exhibit a neural signature of internal error-monitoring (error-related negativity, ERN) after making an incorrect decision (saccadic eye-movement) and before receiving visual feedback. Critically, we find that ERN at 12 months developmentally predicts which of the infants will evidence self-representation (mirror self-recognition) six months later. Infants' self-recognition was predicted specifically by internal error-monitoring, and not by external feedback-monitoring (FRN), nor by infants' age or general development. Moreover, we show that only infants who later self-recognised adjusted their behaviour post-error, by slowing their decisions and increasing visual exploration. Thus, internal error-detection, if available, can be utilised for online adjustments in information-seeking and decision-making as early as 12 months of age. These converging neural and behavioural findings support the idea that, rather than presupposing a self, early metacognition may be functionally involved in building conceptual self-awareness in humans.