As in "flat affect." I think that this fits the context as the term is used in psychology.

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Note added at 8 mins (2009-06-12 20:11:48 GMT)
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Affective flattening is a general category which includes diminishment of, or absence of, emotional expressiveness. It is sometimes inappropriately equated with blunted or restricted affect. "Blunted" is affect that is present but only with minimal degrees of emotions evident. "Restriction" is a holding back as in alexithymia. "Restricted" is not as severe as in flattened or blunted affect.

http://en.wikipedia.org/wiki/Flat_affect

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Note added at 9 mins (2009-06-12 20:12:40 GMT)
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Flat affect: A severe reduction in emotional expressiveness. People with depression and schizophrenia often show flat affect. A person with schizophrenia may not show the signs of normal emotion, perhaps may speak in a monotonous voice, have diminished facial expressions, and appear extremely apathetic. Also known as blunted affect.

http://www.medterms.com/script/main/art.asp?articlekey=26293

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Note added at 10 mins (2009-06-12 20:13:36 GMT)
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Flat affect: absence of or diminution in the amount of emotional tone or outward emotional reaction typically shown by oneself or others under similar circumstances; a milder form is termed blunted affect.

http://www.wrongdiagnosis.com/medical/flat_affect.htm

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Note added at 13 mins (2009-06-12 20:16:02 GMT)
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Schizophrenia patients with flat affect can be distinguished from those without flat affect in several measures, Dr. Raquel E. Gur said at an international congress sponsored by the World Federation of Societies of Biological Psychiatry.

The application of functional MRI can contribute to understanding the neural basis of clinical features of schizophrenia, such as flat affect. "Patients with flat affect showed greater abnormalities in amygdala activation and performed more poorly. There was a paradoxical relationship. Increased activation was maladaptive, leading perhaps to a freeze," said Dr. Gur, vice chair for research development in the department ...

http://www.highbeam.com/doc/1G1-169596572.html