Psychosis is one of the mental disorders with the largest impact due to high personal and family costs. Building research at the very beginning of the psychotic process is crucial to give access to core pathophysiological features of the disease before all the pathological processes are fixed and before medication has side effects on brain function. Recent consensus work points to the need for further basic and therapeutic research in psychosis by applying a staging strategy that would differentiate the earliest stages such as Clinical High Risk for Psychosis (CHR-P) and the full blown First Episode of Psychosis (FEP) from later stages such as Schizophrenia. The direct application of this pathophysiological perspective is to identify the best markers predicting the progression of psychosis. However, while the pathophysiological aspects have been widely explored in schizophrenia, a major research effort is still needed to understand the underlying neural mechanisms and better predict the risk of psychosis progression in the earliest stages. Perceptual disturbances are key elements in the understanding of psychosis. In addition to clinically observed hallucinations and sensory distortions, there is now a large body of evidence for auditory and visual neurocognitive impairment in chronic psychosis. Concerning the early stages of psychosis, while sensory distortions are of high clinical value in assessing the risk of transition, there is still limited data on the underlying auditory or visual neurocognition. The aim of this project is to explore perceptual input and integrated processing in CHR-P patients, in comparison to first-episode psychosis patients and healthy volunteers. We hypothesize neurocognitive disturbances in the early stages, in relation to sensory distortions. We will explore visual processing, with tests measuring the processing of information as it enters the visual system, but also its transformation into a coherent whole, as in a face, as well as the way it is interpreted according to our expectations. We will also study auditory perception, with tests measuring the auditory perception of the input signal as well as the way certain sounds are interpreted in an emotional context. Finally, we will study the way time is perceived. A one-year follow-up in patients with CHR-P will measure whether specific sensory markers predict the risk of transition to psychosis. This project is based on the recruitment of a cohort of patients in four early intervention centres, all supported by research teams known for their works on perception. We will use proven markers of sensory functioning, which have been previously shown to be impaired in chronic psychosis. The research consortium is connected with the RHU Psycare network and will use its recruitment standards.