What is a reaction video?
“Reaction videos are videos in which people react to events. In particular, videos showing the emotional reactions of people viewing television series episodes, film trailers and music videos are numerous and popular on video hosting services such as YouTube.”
The science behind these types of videos.

TwinsthenewTrend
These guys are so energetic and genuine in their reactions to songs and videos and artists, I really enjoy their You Tube channel because it also takes me back to all the old songs that I’d forgotten about.
One of their videos in particular is unforgettable and it was their reaction to The Animals – House of the Rising Sun. I love that song. And so did the twins. I think it was the first time I’d ever seen them mesmerised and not popping out of their seats every 10 seconds. (Insert happy smiley face that they experienced this song).
This is their YouTube channel.
Here is the link to their reaction to The Animals.
And here is a little history about the song itself.