Chambers (2002) cites an example of the application of the apparent-time hypothesis. The study, carried out in central Canada, examined the sociolinguistic variable (wh), where the unvoiced labiovelar glide /hw/ loses phonemic status and merges with the corresponding voiced glide /w/. In this study, the oldest subjects seem to indicate a stable period for this variable, both the 70-79 year olds and those over 80 used the voiced variant where the unvoiced was "expected" 38.3 and 37.7% of the time, respectively. Each subsequent younger age cohort (10 years) shows a greater percentage of /w/ usage, with those 20-29 using /w/ 87.6% of the time and the teenagers using it 90.6% of the time. Notice that the deltas between the oldest two groups and between the youngest two groups are relatively small, 0.6% and 3.0%. Between these two extremes the rate of change between the groups is quite high, approximately 10% per age cohort. This pattern can be described as an initial stable period, followed by a period of rapid change, and a tailing off as the change nears completion. This S-curve pattern has been identified as characteristic for many types of linguistic changes.
Not all age-related variation is indicative of change in progress. It may be an age-graded variation. The applicability of the apparent-time hypothesis should be confirmed by real-time evidence, which actually samples the population over an extended period of time. This is the only true indicator of change in progress. Real-time evidence may come from a longitudinal study of a population or by replicating a study conducted at some relatively distant time and comparing the observations to those previously published.
The Apparent Water Vapor Sinks and Heat Sources Associated with the Intraseasonal Oscillation of the Indian Summer Monsoon
Aug 15, 2011; ABSTRACT The possibility of using remote sensing retrievals to estimate apparent water vapor sinks and heat sources is...