A method of determining at least one behavioral parameter of a wearer for designing an ophthalmic eyeglass lens includes: a) acquiring a first data set from a first representation of the head of the wearer in three dimensions b) determining the relative position in space of at least three particular points of the head based on the data set c) acquiring a second data set from a second representation of the head in a natural posture, including at least one image of each of the three particular points d) identifying the image of each of the particular points from step b) on the representation of step c) e) deducing information relating to the position and/or to the orientation of the head of the wearer during the determination of the second representation from this identification and f) determining the behavioural parameter of the wearer based on the information from step e).
