The question is about this video.
Summary of the Video: (can skip if you watched it)
The only audio is "elevator music." There is a man who communicates only with written orange signs. He asks the viewers to quickly perform some easy arithmetic calculations, and he shows the answer to each one after a few seconds:
$5+3 \ \ = 8$
$9+2 \ \ =11$
$10-6=4$
Then, he asks the viewer to quickly pick a number between $5$ and $12$. At this point, I suddenly felt a sense of urgency, and rapidly picked $7$; it was the only number I could think of in that second. Of course at the end of the video, the man guessed that the subject picked $7$.
Question:
How does this video influence the viewer to pick $7$? More generally, what techniques do these types of videos employ to try to manipulate the subject into chosing a certain outcome?
I tried to look for certain patterns in the calculations and I found a diagonal symmetry, but I'm not sure if it's relevant:
$\color {red}{\text{odd}} \ \ + \color {red}{\text{odd}}$
$\color {red}{\text{odd}} \ \ + \color {blue}{\text{even}}$
$\color {blue}{\text{even}} \ + \color {blue}{\text{even}}$
I've also noticed that the average of the $3$ results is $\dfrac {8+11+4}{3} = 7. \overline {6}$