A new kind of interaction: interaction with a shadow of other people.

"In 1973 Krueger coined the term ‘artificial reality’ to describe the responsive environments he created as part of his doctoral research on human-computer interface design. [...] Although the term was not widely adopted, the idea was and Video Place is arguably the first work of art to employ what came to be known as virtual reality."[1]

[1] Edward A.Shanken, Art and Electronic Media,p.166