3.1. Economy Principles.

In van Gelderen's model, the two internal motivating forces of grammaticalization are the HPP and the LMP. These principles have dual status. On the one hand, these “are principles of Economy that work in grammars of speakers.” On the other hand, these principles “lead children to build their grammars in a particular way” (p. 12).⁶

Further, although economy played a major role in early Minimalist theorizing, economy no longer plays a key role in current work. For example, the assumption that it is less economical to merge early and then move than to wait as long as possible before merging (that is, Merge over Move, van Gelderen's LMP) no longer holds true. Instead, now Merge comes in two flavors: Internal Merge and External Merge, replacing Move and Merge, respectively (Chomsky 2004)

On the second view, economy principles are biases on the language acquisition process. This view of economy has played a key role in generative work on morphosyntactic change (Lightfoot 1979, Clark and Roberts 1993, Roberts 1993, Kiparsky 1996, Roberts and Roussou 2003, Haeberli 2004). For example, Roberts and Roussou (2003) define the markedness of parameter values in terms of a simplicity metric, where, for example Merge is less marked than Move. In the absence of cues for marked parameter values such as inflectional morphology, the less marked option is taken in acquisition.⁷

Do the two views on economy described above have different empirical consequences? The idea that (something akin to) economy principles are part of the processing mechanisms that employ linguistic competence has been explored in recent work, particularly in the area of word order variation and change. For example, Hawkins (1994, 2004) argues that parsing principles influence generation, and that more easily parsable variants will be used more frequently than less easily parsable variants. In contrast, Kirby (1999) equates parsability with learnability, as in the second view of economy described above. Briscoe (1998) discusses computer simulation work that suggests that either Hawkins' model or Kirby's model, or a combination thereof, accounts for language change in favor of more parsable variants.

Further, economy principles may also influence comprehension. Recent psycholinguistic work has explored the different empirical consequences of production/speaker-based versus comprehension/hearer-based accounts of linguistic variation (see especially Wasow 2002; also Jaeger 2005 and Jaeger and Wasow 2005 on that-omission in complement and relative clauses). It would be interesting to explore the diachronic consequences of competing production and comprehension interpretations of the HPP and the LMP.

3.2. Internal and External Principles.

Lightfoot (1979) and Roberts (1993) rely solely upon internal economy principles to capture directionality in language change. For example, Roberts (1993) (also Clark and Roberts 1993:335) proposes a principle of language acquisition, the Least Effort Strategy. The Least Effort Strategy claims that language acquirers will prefer grammars that assign the most compact or simplest representations to the input string. As Lightfoot (1999:219) points out, if economy principles determine language change, why should there ever be systems that violate these principles? Van Gelderen's answer is that internal factors interact with external ones.

As van Gelderen notes (pp. 12, 262), the notion that language change involves an interaction between internal and external forces has been around for a long time (Jespersen 1922: Chapter 14,§6). Keller (1994:100), Kiparsky (1996), and Wu (2004) also propose accounts of language change that involve the interaction between internal and external forces. However, it is possible to critique competing forces accounts on methodological grounds, since there is typically an ad hoc search for external forces to match the phenomena that need explanation. One way to avoid this problem is to use computational models of language change, use, and acquisition (Briscoe 2002, Cangelosi and Parisi 2002). Computer simulations enable us to model different explanations for language change and explore the consequences of varying side conditions. For example, Briscoe (1998) utilizes computer simulations to show that an adequate model of language change must include at least internal learnability factors and counteracting external pressures, such as expressivity.

In van Gelderen's model, internal forces such as the HPP and the LMP interact with external forces such as prescriptive prohibitions, borrowing, and expressivity. For example, as noted above, van Gelderen argues that to undergoes a category change from P to I, and from I to C. Attested examples of to in I and C are given in 7 and 8, respectively (p. 247).

Van Gelderen (pp. 242–244) provides several arguments that to appears in C in examples such as 7. However, her arguments are somewhat problematic.

First, she claims that to not does not occur with the complementizer for (versus, for example, she prefers for me not to stay on the phone for very long). Note, however, that sequences of the form X prefers for Y to not, as in The WWE prefers for wrestlers to not have a personal webpage may be easily found.

Second, van Gelderen provides evidence from the British National Corpus that in raising constructions seem does not occur with to not (where to in to not is claimed to be in C). This is taken by van Gelderen to favor her analysis because it is widely assumed that in raising constructions seem takes an IP complement, and never a CP complement. However, it is also easy to find naturally occurring instances of the sequence seems to not, as in Javascript seems to not be working.

Third, according to van Gelderen, to must immediately precede the ellipsis site in VP ellipsis, as in They suggested I call the police but I decide not to __ / *to not __ (see Huddleston and Pullum 2002:1526). As indicated above (see note 4), this provides support for van Gelderen's position that to is not an auxiliary verb, but does not necessarily provide support for her position that to is in the head of CP.

Fourth, van Gelderen argues that the existence of to not to sequences as in This is to try to not to overturn the … supports the claim that to can appear in either I or C. Sequences of this sort with to not to are indeed frequent. However, just like the previous arguments, it does not provide powerful evidence in support of analyzing to as a clausal subordinator in C.

In sum, (i) as noted in footnote 4, there are clear differences between clausal subordinators such as that and for) on the one hand, and to on the other hand, and (ii) there is compelling evidence that to is not an auxiliary verb, but a VP subordinator (Huddleston and Pullum 2002:1185–1186).

Putting the question of infinitival to's categorial status aside, the problem that 7 and 8 pose for the LMP is why to is not always in C, as in 7. One possible explanation van Gelderen suggests (p. 248) is the prescriptive rule against splitting infinitives in English (Quirk and Greenbaum 1973:312). This is an interesting claim, but much more has to be said in order to establish its plausibility.

First, it is interesting to note that the rule against the split infinitive did not arise until the second half of the nineteenth century (Huddleston and Pullum 2002:581). Split infinitives had been in use for several hundred years (since the 14th century), becoming popular in English writing during the nineteenth century. A way to provide support for van Gelderen's hypothesis would be to track the frequency distribution of the split and non-split infinitive variants and see if a change in the distribution of these variants is correlated with the emergence of the prescriptive rule.

Second, the split infinitive is obligatory in certain cases, for instance with prepositional modifiers, as in We expect it to more than double versus *We expect it more than to double (Zwicky 2004). Third, promiscuous application of the rule against split infinitives can create ambiguity, as seen in 9 and 10 (Huddleston and Pullum 2002:581–582). In 9, which violates the rule against split infinitives, immediately unambiguously modifies approve. In contrast, 10 is ambiguous.

Fourth, it is not clear that “the rule against splitting infinitives is still very strong in standard English” (p. 248). As Huddleston and Pullum (2002:582) point out, “modern usage manuals […] present the rule only with the qualification that a ‘split infinitive’ is acceptable if it improves clarity or avoids awkwardness.”

Summing up, the idea that prescriptive pressures compete with economy principles is an intriguing one, but there is a tremendous amount of empirical and theoretical work that needs to be done in order to demonstrate this interaction in particular cases.

3.3. Formal versus Functional Explanations of Grammaticalization.

Grammaticalization as Economy is a part of a recent trend in the historical linguistics literature to give formal accounts of grammaticalization within the Principles and Parameters framework (van Kemenade 2000, Roberts and Roussou 1999, 2003, Batllori, Hernanz, Picallo, and Roca 2005), thus attempting to bridge the gap between formal and functional accounts of language change. Under these approaches, a complete theory of grammaticalization involves only two components: (i) an account of how trigger experiences become ambiguous, and (ii) a theory of language acquisition (and/or generation, see section 3.1) that employs economy principles (that is, biases for certain derivations over others). For van Gelderen, as well as the other proponents of formal accounts of grammaticalization cited above, it is sufficient to have a model of how the cognitive process of language acquisition maps the trigger experience to knowledge of language.

However, this approach falls short of a complete account of language grammaticalization.⁸

The formal accounts of grammaticalization cited above typically focus entirely on the cognitive processes involved in language acquisition and/or generation. In contrast, Traugott (2003:21) argues that language change is “the result of strategic interaction, specifically of choice-making on the part of speakers/writers in interactional negotiation with addressees/readers. This includes, but is not limited to, conveying of information.” An account of grammaticalization like Traugott's does not exclude internal factors such as the ones identified by van Gelderen and others. Rather, such a view implies that a satisfactory model of grammaticalization cannot rely entirely on an explanation of how trigger experiences change and a theory of language acquisition, but must also include a model of the cultural process that mediates between the context of language use and the cognitive structures that encode linguistic competence.