In their minds
The first attempts to read humans thoughts had been made several decades ago. Especially in the period of the cold war, were made experiments for the ability to read and record human thoughts, even for mind control, generating ethical and political issues.  
Today, scientists are trying to cartography brain, linking the activity of its regions with specific words or pictures so they understand how human mind works for various medical and non-reasons, but also to attempt creating artificial intelligence.  
This project consists of diptychs in which the first image has human presence while the second does not.
It's a photographic attempt via conceptual, or visual connotations, or even abstracted correlations, so to ''read'' their deeper conscious or unconscious thoughts of those people, at that specific moment of the click.
Of course this is my arbitrary approximation between reality and my imagination and everyone could make his own speculates.