  Understanding the mechanisms underlying the emergence of leadership in
multi-agent systems is still under investigation in many areas of research
where group coordination is involved. While leadership has been mostly
investigated in the case of animal groups, only a few works address the problem
of leadership emergence in human ensembles, e.g. pedestrian walking, group
dance. In this paper we study the emergence of leadership in the specific
scenario of a small walking group. Our aim is to unveil the main mechanisms
emerging in a human group when leader or follower roles are not designated a
priori. Two groups of participants were asked to walk together and turn or
change speed at self-selected times. Data were analysed using time-dependent
cross correlation to infer leader-follower interactions between each pair of
group members. The results indicate that leadership emergence is due both to
contextual factors, such as an individual's position in the group, and to
personal factors, such as an individual's characteristic locomotor behaviour.
Our approach can easily be extended to larger groups and other scenarios such
as team sports and emergency evacuations.
