David Banks wrote at 18:27 on October 30 2014 to sysfling:
The simple (but brutal, and with all due respect to all the other contributors) is that there are no distinguishing criteria because behavourial process does not exist. What is usually discussed under this heading is a rag-bag of unrelated phenomena that do not form a coherent category. The phenomena in question are better dealt with at a more delicate level than that of process types. My article on this question is forthcoming in a book edited by Donna Miller and Paul Bayley.
 Halliday & Matthiessen (1999: 135-6) provide some grammatical reactances which distinguish behavioural from other process types and which thus identify what they have in common:
- 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).
Criteria for distinguishing process types are listed in Table 5(45) in Halliday & Matthiessen (2004: 301).
 The existence, or not, of metalinguistic distinctions depends on whether or not they are projected into semiotic existence as ideas and locutions by linguists. This depends, in the short-term, on whether or not they prove useful, and in the long term, on whether they are consistent with the other distinctions on which they depend.
- '‘behavioural’ process clauses are not so much a distinct type of process, but rather a cluster of small subtypes blending the material and the mental into a continuum' (2004: 255), and
- 'these can be interpreted as a subtype of material processes or as a borderline category between material and mental' (1999: 136).