LSD or Lysergic Acid Diethylamide is also known as acid.
This is a super psychedelic drug and it has a mind-bending psychological effects such as overly-saturated colors, swirling walls and intense emotions.
This dude is in a heavy acid trip. He may walk, talk and do other business but his mind is playing an intense game with him. We can never know how he is feeling at that moment but we can only see his movement.
Scientists say you can not predict effects of LSD. The first effect starts within 3o-90 minutes after taking it and then followed by various range of emotions , delusions and extreme visual hallucinations.