flat affect n., <flat af-fekt> {psychology}

Flat affect is a possible negative symptom of schizophrenia. It involves a lack of emotion or expression of emotion. For instance, the person could be describing an encounter during which he or she was robbed, but without any hint that it was scary, shocking or otherwise out of the norm. The person simply does not express emotions that would "usually" be present in a given situation.

{Thanks to deep thought for the heads up}