Loki's eyes flew open at the jerk of the arm, so he got a solid view of Thor punching himself in the head and falling over. "...I wish that had been intentional."

Despite the words, he joined Thor on the floor, fingertips glowing green again, gestures encompassing both the new possible-concussion as well as the cut. He knew how hard Thor could punch. It wasn't outside the realm of possibility that this experimentation had actually hurt him non-trivially.

'Persuasion' hadn't worked, force hadn't worked. He might as well try Thor's way and just... do something. It wasn't really a choice, it was almost instinct.