looking at a hypothesis favorited by much of the ..
Types of Errors in Hypothesis Testing | UniversalClass
Moving to the other side of the dissociation, since it is hard to sayexactly what about language is disrupted in cases of SLI, it isdifficult to determine whether this disruption is specific tolanguage, let alone grammar. While researchers like Van der Lely andChristian 2000, and van der Lely and Ullman 2001 argue that there isa purely grammatical form of the deficit, which does support thehypothesis of a grammar module, this is controversial, as we have seenabove. Certainly consideration of the KE's does not support such ahypothesis. Their root deficit appears to concern orofacial praxis,rather than language specifically; and in addition, their‘general intelligence,’ as measured by tests of non-verbalintelligence, while “normal,” nonetheless appears to havebeen affected by their neurological and/or linguistic abnormalities— witness their scores 18-19 points lower than those of theirrelatives. It is, in other words, unclear that there is anydissociation of language and general intelligence in this case atall. One can conclude that as things stand now, SLI seems to be soheterogeneous a disorder as to defy neat characterization, and thatconsideration of this disorder does not support the view that there isa language or grammar module that functions independently of othercognitive processes.
How to Plan and Write a Testable Hypothesis - wikiHow
On the other hand, however, there is evidence that FOXP2 isparticularly implicated in vocal learning and expression. First, it ishighly expressed in songbirds that modify their innate vocalrepertoires: in canaries it is expressed seasonally, when adult birdsmodify their songs (Teramitsu et al. 2004) and in zebrafinches, it is expressed more at the time when young birds learn theirsongs (Haessler et al. 2004). In addition, there is evidencethat the variant of the FOXP2 gene that is present in humans hasundergone strong positive selection in the hominid line (Enard etal 2002; Zhang et al. 2002). The protein produced byhuman FOXP2 differs in just three out of its 715 constituent aminoacids from that of the mouse, and a recent analysis (Zhang etal. 2003) indicates that two of these differences are unique tothe hominid lineage. According to Enard et al 2002, the factthat these two differences are fixed in the human genome, whereas nofixed substitutions occurred in the lineage of our closest relatives,the chimpanzees, suggests that those changes were strongly selectedfor in our lineage; Enard et al. put the date of fixation ofthese changes in the human population at around 200,000 yearsago. This date accords well with at least some estimates of theemergence of modern human language, suggesting that the vocalcapacities underwritten by FOXP2 — and impaired in those lackingthe gene — are after all critical to language competence.