To understand more about the neural underpinnings for leading and following is the driving force behind this thesis. To do so, there is a need to study leading and following on a basic level. For study I, an fMRI study of neuronal reactivity during leading and following, a minimal model was developed to study leader and follower behavior in a standardized way. This model uses finger tapping of rhythms representing the core of the interactions during leading and following. Participants are invited to both lead and follow, and no expertise is expected. The status difference between the leader and follower is not a part of the model. Data collection is made in Japan, and most of the analyses are carried out in Sweden. In study II the Swedish Universities Scales of Personality is translated from Swedish to Japanese. Personality can be described as a crucial feature in a person’s social and emotional functioning; they are relatively stable over the course of a lifetime. Three dimensions representing personality facets probably relevant for leading and following are emotional stability, extraversion, and agreeableness. Study II resulted in SSPJ-11 with eleven reliable personality scales representing theses three facets relevant for leading and following. Study I presented an effective model to investigate leading and following during fMRI scanning. This model can be used with other designs for further brain imaging and behavior studies. From Study I, it became clear that the neuronal reactivation for leading and following largely overlap, with some specific differences in insular, temporal, and cerebellar reactivity. These results could be a first step towards a revealing the crucial components of neuro reactivations for leading and following.