In the colloquial Phnom Penh dialect of Khmer (Cambodian), lexical use of F0is emerging together with an intermediate VOT category and breathy phonation following the loss of /r/ in onsets (e.g. /kruː/ ‘teacher’ > [khṳ̀ː]). I show how this
incipient tonogenesis might arise in a series of computational simulations tracing the evolution of multivariate phonetic category distributions in a population of ideal observers. Acoustic production data from a fieldwork study conducted in Phnom Penh was used as the starting point for the simulations. After establishing that the basic framework predicted relative stability over time, two possible responses to a phonetic production bias were considered: one in which agents correctly identified the source of (and thereby compensated for) the effects of the bias, and one in which agents misattributed the acoustic effects of the bias as a property of the onset. Good qualitative fits to the empirical production data were found for the latter group of learners, while the outcome for compensating learners resembled production data from a related dialect. These results are consistent with the sudden and discontinuous nature of many sound changes, and suggest that what appear to be enhancement effects may also emerge under different assumptions about the number of cue dimensions accessible to or deemed relevant by the learner.