If you look closely at the data, the effect was stronger in lanes 1 and 8, and weakest in lanes 4 and 5, which implies that the current was circular. This means

If you look closely at the data, the effect was stronger in lanes 1 and 8, and weakest in lanes 4 and 5, which implies that the current was circular. This means that those in the outside lanes would get a bigger boost than those in the inside lanes.