Fighting in broken formation. The competition between the Germanic strong ablaut classes and weak suffix inflection in an agent-based model

In present-day English, Dutch, and most of their Germanic siblings, the verbal weak inflection offers a well-established and regular strategy for forming the past tense. In contrast, the strong inflection seems to present no more than a diminishing rubble of vowel sub-rules and irregularities (Harbert 2007: 277). Still, things were once different. As an innovation specific to Proto-Germanic, the fledging weak dental suffix had to compete with a sturdy strong ablaut-system inherited from Proto-Indo-European, which is assumed to have been both clearly regular and dominant in frequency (Bailey 1997: 8). Earlier computational models of this competition have either focused exclusively on language acquisition (Rumelhart and McClelland 1986; Pinker and Prince 1988; Marcus et al. 1995; Taatgen and Anderson 2002), on the role of acquisition in language change when the weak inflection was already well-established (Hare and Elman 1995; Yang 2002), or have explicitly disregarded the regularity of the strong system (Colaiori et al. 2015; Pijpops and Beuls subm.). However, these models don’t address how a nascent weak inflection could have possibly gained enough momentum to overthrow a both regular and dominant strong system. To explain this enigma, several proposals have been put forward in the historical literature (Ball 1968: 164; Bailey 1997: 17). The first states that the dental suffix is in principle applicable to all verbs, while each separate strong vowel alternation is not. That is, the strong system presents a broken formation of several vowel alternations against a single dental suffix. The second holds that even as a whole, the strong system was not applicable to some particular verbs, which would then create a safe nest for the weak inflection to mature. The last posits that the regularity of the strong system was being undermined by sound changes, allowing the weak inflection to take advantage of the created irregularities. To investigate whether these causes can indeed be responsible for the ascent of the weak inflection, an agent-based model was created in which the focus lies on language use rather than acquisition (cf. Croft 2000; Bybee 2010). The model has been integrated into the Babel2-framework (Loetzsch et al. 2008), and the competing constructions have been implemented in the Fluid Construction Grammar formalism (Steels 2011; van Trijp et al. 2012). The model’s behavior showed that, in the long run, the first explanation alone already suffices to explain the rise of the weak inflection, even if each separate vowel alternation starts out more frequent than the weak inflection. This finding of course does not say that the second and third proposals did not help in creating more optimal conditions for the weak inflection to start its ascent. It does mean, however, that the disintegration of the strong system might be the result and subsequent catalyst rather than the original cause of the rise of the weak inflection. That is, perhaps both are related through a push chain, rather than a drag chain.status: publishe