The natural mental ability all people possess that allows them to quickly and dynamically
assess the situation and environment they are in to decide whether or not it is
practical to masturbate at the exact moment in time.
My mother wasn't due to
be back home for another 10 minutes, so I thought I'd
slip in a quick wank. However, masturbatory contingency told me that it wasn't worth taking any chance of her walking in on me.