Does accent and phonation type affect the locus equations of British English accents?

The theory of locus equations argues that the brain stores ‘target values’ representing CV structures for the purposes of both articulation and perception. Locus equations are linear regression lines that represent the second formant frequency (F2) at the start of consonant-vowel (henceforth CV) transitions to the F2 at the middle of the vowel, measured in hertz. Not only does this allow for loci values to become consonantal phonetic descriptors, their degree of slope becomes a measure for the CV structure’s resistance to coarticulation. For this reason, their empirical precision is vital for their use in developing speech synthesis software, and for a deeper understanding of linguistic sound systems utilised in linguistic fieldwork. Thus, an exploration of locus equations in an intra-language domain is essential in discovering whether phonemes possess the accent and phonation characteristics, or whether accent and phonation is derived from connected speech influenced by coarticulation. Prior to the present study, locus equations have only be examined cross-linguistically, brought to prominence by Sussman et al in 1991. However, they have yet to be examined in an intra-language domain with manipulated independent variables. This means there is no basis to determine whether the data supports locus equations, or its theoretical opposite, exemplar theory, which hypotheses tokens are stored in the brain as activation ‘clouds’ as examples of a given phoneme. The current study is divided into two experiments with a view to determining whether differences in accent and phonation type conform to locus theory. The first is a seminal pilot study which asked twenty participants to organise six squares by their colours, with the premise being that they will either organise them into examples of a particular colour, such as crimson to red, or they will sort crimson and red into two entirely separate groups. Provisionally, the hypothesis predicts that the subjects will be strict in their categorisation and produce groups containing only one variety. For Experiment II, six different participants, with an even gender divide and possessing either a Yorkshire, Devon or Essex accent, were asked to produce 180 CV structures each. These were embedded in carrier phrases, using vowels from each corner of the quadrilateral and the schwa, and six plosives in modal voice and whispering for each token, in order to gauge the affect of phonation, as well as accent, on the locus. The provisional hypothesis for this experiment is that there will be little variance among accent - thus meaning the invariance in the speech signal may come from elsewhere - and in terms of phonation, that due to lack of alternative high and low velocity air pressure that opens and closes the glottis, the Bernoulli effect will be mitigated, and therefore the loci values will be lower due to the lower-pressure burst of plosive articulation.