Methods

EEG 

The human brain comprises billions of neurons, small nerve cells that communicate with each other through weak electromagnetic signals. These signals vary depending on what we see, hear, or do, as different brain regions interact to process information. An electroencephalogram (EEG) is a non-invasive technique that detects these electrical signals using small electrodes placed on the scalp. By recording changes in the signals over time, the EEG helps identify when and where brain activity occurs. The data collected is then analysed with computer software and linked to observed behaviours or sensory stimuli.
The EEG is the ideal tool for our investigations. It provides excellent temporal resolution and is sensitive to subtle changes in neural activity, even those that may not be overtly reflected in behaviour. Indeed, unlike behavioural studies that are based on the observation of overt responses reflecting the outcome of complex neural processes, the EEG provides fine-grained information on the timing and neural basis of cognitive processes. In our studies, we measure the event-related potentials (ERPs) measured via EEG.

FACS

The Facial Action Coding System (FACS) is a standardised method for describing and analysing facial movements. Developed by Paul Ekman and Wallace Friesen, FACS identifies and categorises facial expressions based on the activation of specific facial muscles, referred to as Action Units (AUs). Each Action Unit corresponds to a distinct muscle or group of muscles, enabling to decode complex facial expressions into their basic components.
In our studies, we employ FACS to identify a specific facial configuration corresponding to the Duchenne smile (or enjoyment smile).