According to the working memory model, which accounts for the organisation of working memory, the processing of non-meaningful gestures is not clear. Some authors suggest that working memory for non-meaningful gestures has the same characteristics as the phonological loop, made up of a phonological store and of a revival process (articulatory rehearsal). These characteristics are evidenced in memory span tasks, memory span which is itself determined by the duration of the memory trace and the time required to refresh the trace by subvocal rehearsal.

The investigators therefore aim to set up a gestural working memory task, which is specific, simple and reproducible, in the manner of verbal and visuospatial span tasks. It will first be an exploratory and descriptive study with healthy subjects.

In the first instance, each subject performs the gestural working memory test. The test is based on the model of verbal or visuospatial working memory tests. Video clips that display the movement of two, then three, then four different fingers are shown to the subject, who must then reproduce them. There are nine different sub-tests: forward span and backward span for both hands then for each hand, i.e. six sub-tests, in addition to three sub-tests with concomitant interference tasks (verbal, gestural or both). Each sub-test comes to an end when the subject fails both attempts of the same item. The entire test takes approximately 30 minutes.

A questionnaire is then handed to the subject: the subject provides their full name, date of birth, profession, education level (number of years of study post compulsory education), laterality, as well as potential professional or leisure activities that might involve fine finger movement. They also complete the Edinburgh Handedness Inventory assessment.

In order to correlate this new test with other validated tasks, each subject is then required to perform a verbal and visuospatial working memory task: the digit span test and then the spatial memory test, which last approximately 10 minutes.

The entire protocol lasts approximately 45 minutes per subject. The data is then anonymized and processed confidentially.

Inclusion Criteria:

• healthy adult volunteers
• 18/50 years old
• they must speak fluent French and give their informed consent

Exclusion Criteria:

• neurological or psychiatric disorder
• uncorrected visual or hearing loss