This paper examines how children acquire Spanish variable clitic placement (VCP), a lexically conditioned phenomenon whereby clitics may precede or follow complex verb phrases. Research on how children acquire truly syntactic variable phenomena suggests that they either generalize one variant initially or they match the variation in the input from the beginning. Here I examine how children acquire the lexical conditioning of Spanish VCP. A corpus study of naturalistic conversations between parents and young children suggests that from the earliest ages examined (2;0-3;0) children display lexically-specific patterns that seem to be fine-tuned by the early school years. Experimental results using two different elicitation techniques with children ages 4;0-7;0 provide further support for early acquisition of the lexical conditioning of VCP and some evidence for fine-tuning during this age window. Thus, methodological triangulation enables detection of variable use where children would otherwise show categorical use of variants with infrequent syntactic phenomena, such as Spanish VCP.

Romance clitics are currently accounted for as DP arguments moved to functional head positions or as functional heads (AccVoice, etc.) licensing pro-DPs in argument position. I take the view that clitics are first merged as heads, projecting independently motivated categories on the functional spine of the sentence (φP, ApplP). I argue that they can satisfy theta relations without need for a pro associate. From an empirical point of view, a pure head syntax for clitics is favoured in explaining the asymmetries between clitics and phrases, found in several syntactically relevant domains (order, agreement, case). I show how the hypothesis that clitics are functional heads derives the internal order of the clitic string, which does not necessarily match (or mirror) that of phrasal constituents. I also consider agreement asymmetries (perfect participle agreement) and case asymmetries (in relation to Differential Object Marking).

It has been argued that the development of the Swedish possessive -s constitutes an example of degrammaticalisation because it has changed from being an affix to being a clitic (Norde 1997; 2001a, b). I argue that a simple distinction between affix and clitic cannot capture the development of this element, instead a distinction in two dimensions need to be made; PLACEMENT needs to be distinguished from DEGREE OF ATTACHMENT. Furthermore, I claim that the distinction between agreement and once only marking represents yet another dimension. With respect to the Swedish possessive, as Norde (1997) shows, there has been a clear change from agreement to once only marking; however, I argue that this change does not tell us anything about the element's morphological status. With respect to placement, -s is still subject to competing constraints and with respect to attachment, there is some evidence of morphological interaction between the -s and the word to which it attaches. It is then inappropriate to call the Swedish possessive -s a clitic and to refer to the change which it has undergone as degrammaticalisation.