motivation

For Tyson, perhaps the lure of the limelight was too much to stay away from, and the several millions also provided added motivation.

Animals previously exposed to THC in utero display a dramatically increased motivation to press a lever that would deliver a dose of opioid drugs compared to those that were not previously exposed to THC.

Facing his old team could provide a sliver of extra motivation for a player who already seems like a man on a mission.

With Paul reported to be earning about £31m and Tyson's purse half that, there are question marks around the motivations behind this match-up.

"We must know the motivation behind the attacks, and to re-establish peace and safety as fast as possible."