Since the 19th century, perception has been regarded as an inferential process in which sensory input is compared with prior knowledge, namely the internalised representation of the visual environment. This notion is central to the understanding of everyday perception and cognition in general, and is attracting much attention in various areas of psychology and cognitive neuroscience. However, it is unclear whether and how the primary visual refinement that is thought to underlie the convergence of bottom-up inputs with top-down prior knowledge applies to the processing of meaningful stimuli in our everyday lives. The investigators have shown that human face processing mechanisms are shaped by prior knowledge that the horizontal range of face information conveys the richest and most reliable cues. Furthermore, investigators' previous data suggest that the primary visual cortex is recruited during the progressive refinement of face representation. Using very high field neuroimaging, the present project proposes to follow the neural mechanisms underlying the cortical refinement of horizontal information in human face processing, and to study their contribution to behaviour.

Inclusion Criteria:

Participants will be screened (see annex 2) to ascertain they fit with all these inclusion criteria:

• Be between 18 and 50 years old,
• have normal eyesight or eyesight corrected with contact lenses,
• Have no neurological disorder,
• Not have had a skull fracture or head surgery,
• Have no chronic progressive illness or mental deficiency,
• Have no metal parts in their body (dental braces or pins, metal plates, pacemakers, implanted prostheses, etc.),
• Have no tattoos containing metallic particles or implanted jewellery (e.g. piercings) that cannot be removed,
• Not to have worked with metals,
• Do not take any medicines or substances that may affect brain function (e.g. drugs, energy drinks, alcohol),
• Not to be pregnant or breastfeeding.
• Do not be claustrophobic.

Exclusion Criteria:

Participants presenting a counter-indication (responding yes to one of the questions of the screening questionnaire, see annex 2) to participate will be excluded from participation.

Participants will be screened to ascertain they do not present any of these counter-indications to the participation to the MRI measurement. We will exclude people with these characteristics:

• Be younger than 18 or older than 50 years old,
• have poor eyesight,
• Have neurological disorder,
• have had a skull fracture or head surgery,
• Have a chronic progressive illness or mental deficiency,
• Have metal parts in their body (dental braces or pins, metal plates, pacemakers, implanted prostheses, etc.),
• Have tattoos containing metallic particles or implanted jewellery (e.g. piercings) that cannot be removed,
• have worked with metals,
• take medicines or substances that may affect brain function (e.g. drugs, energy drinks, alcohol),
• pregnant or breastfeeding.
• claustrophobic.