LAMSAS in the Netherlands

Fieldworker effect

Fitting

This page describes an attempt to compensate for the fieldworker effect.

data:      raw phonetic strings, no lexical variants
subset:    fieldworkers: Lowman, McDavid
           worksheets: Middle Atlantic, South Atlantic
           1030 informants
grouping:  fieldworker + worksheet + community: 461 locations
               (two locations merged because of identical coordinates)
method:    Levenshtein
maps:      stochastic clustering, group average + weighted average,
               followed by classical MDS on cophenetic differences

The plot below shows the average phonetic difference as a function of geographic distance. There are three sets of differences: differences within data collected by Lowman, differences within data collected by McDavid, and differences between data from Lowman and data from McDavid.

The phonetic differences between Lowman data and McDavid data is consistently higher than differences within each set of data. This strongly suggest that Lowman and McDavid transcribed identical sound in a different manner.

The plot below shows the standard deviation of the phonetic differences as a function of geographic distance. Again, there is a striking differentiation.

We use polynomial fitting to model both mean and standard deviation of dialect differences as a function of geographic distance. We do this for all dialect differences, as well as for each of the three subsets. Then we use these models to correct each subset towards the overall mean and standard deviation. (See graphs of fitting, PostScript.) The plots below show the corrected data.

Below are dialect maps of uncorrected and corrected dialect differences. Grey areas are for data from fieldworkers other than Lowman and McDavid, and/or from worksheets other than Middle Atlantic and South Atlantic.


uncorrected


corrected


uncorrected	corrected

Fitting seems to work quite well in the north, but doesn't have any visible effect in the south. Note that Pennsylvania doesn't gain new dialect borders. They just don't show on the big map of uncorrected differences, because it shows only the most distinctive clusters.


uncorrected	corrected


uncorrected	corrected

Guy Lowman
Traditional maps
Fieldworker effect
	Fitting
Worksheet effect
	Fitting
To do