Can we say that in German all reflexive verbs use either haben or sein as an auxiliary verb in perfect tense?
For example can we say all reflexive verbs use haben only, and never sein?
Can we say that in German all reflexive verbs use either haben or sein as an auxiliary verb in perfect tense?
For example can we say all reflexive verbs use haben only, and never sein?
A preliminary issue we cannot really get around is defining "reflexive", which is, unfortunately, used rather inconsistently. There are those who would consider sich ausweichen (which someone mentioned in the comments) a type of reflexive (reflexively used) verb. If you do that, it gets harder to formulate rules based on reflexivity. I, and probably a majority of linguists today, would call verbs of the type sich ausweichen "reciprocally used". Rather than giving you a formal definition, I will just point out that with reflexive(ly used) verbs as understood by the majority, you can basically explain the meaning by mentally "clarifying" the pronoun as sich selbst (as in sich freuen), while with reciprocally used verbs, you would explain the meaning by mentally clarifying it as sich gegenseitig/wechselseitig or einander. A (hopefully) instructive example: Anna und Bernd betrachteten sich im Spiegel. This can be interpreted both reflexively (Anna looked at her picture and Bernd looked at his picture in the mirror), or reciprocally (Anna looked at Bernd's picture and Bernd looked at Anna's picture in the mirror). It should be clear from this that sich ausweichen falls in the latter category, and sich freuen in the former.
Having made the above distinction, we are left with the following rules (see also, Helbig/Buscha, Deutsche Grammatik, 2001, § 1.7.2.1; IDS/Grammis, Der Formenbestand des deutschen Tempussystems: haben oder sein?):
(1) The perfect auxiliary verb of a reflexive(ly used) verb is haben. (Anna hat sich gefreut. Bernd hat sich erkältet.)
(2a) The perfect auxiliary verb of a reciprocally used verb taking accusative case is haben. (Frau Müller und Herr Müller haben sich verklagt. Die Kinder haben sich angefreundet.)
(2b) The perfect auxiliary verb of a reciprocally used verb taking dative case is sein or haben, and is the same as the perfect auxiliary verb of its non-reciprocally used version. (Anna und Bernd sind sich ausgewichen. Anna und Bernd haben sich geähnelt.)
(A word of caution for the advanced learner: In German, reflexive verbs can, in some cases, appear as non-converse verb forms where they behave similar to adjectives. These can look very similar to a perfect form with sein. Compare: sich beschäftigen. Present perfect: Er hat sich mit dem Projekt beschäftigt. But there is also: Er ist mit dem Projekt beschäftigt. These forms are always correlated to an (active) statement with a reflexive, in this case: Er beschäftigt sich mit dem Projekt. Such forms also exist where there is an alternative werden passive, in which case we have a type of sein passive, e.g. sich duschen - Er ist geduscht. As you can see, however, in all of these forms there is no longer a reflexive pronoun, which is how you can easily distinguish them from an ordinary perfect form.)