(Mostly) from Halliday & Matthiessen (1999: 135-6).
- Like material clauses (but unlike mental clauses) the unmarked present tense in behavioural clauses is present-in-present (he is watching) rather than the simple present (he watches).
- Behavioural clauses include conscious processing construed as active behaviour (watching listening, pondering, meditating) rather than just passive sensing (seeing, hearing, believing).
- Like the Senser in a mental clause, the ‘Behaver’ in a behavioural one is endowed with consciousness; whereas in other respects behavioural clauses are more like material ones.
- Like material clauses (but unlike mental ones), behavioural clauses can be probed with do: What are you doing? — I’m meditating but not I’m believing.
- Behavioural clauses normally do not project, or project only in highly restricted ways (contrast mental: cognitive David believed —> the moon was a balloon with behavioural: David was meditating —> the moon was a balloon;
- Behavioural clauses can not accept a ‘fact’ serving as Phenomenon (mental: David saw that the others had already left but not behavioural: David watched that the others had already left).