Patterns of the use of AUX-OP in Deaf NGT signers and NGT-Dutch interpreters.

There is an auxiliary verb in NGT glossed as AUX-OP which is used to mark agreement
relations in (non)agreeing verbs.
It has been noted by the Dutch Sign Centre that the usage of AUX-OP in NGT has been increased, most notably within the group of sign language interpreters.
Thus the aim of this experimental study was to investigate whether this claim is justified. Analysis of the usage of AUX-OP shows that the average usage of AUX-OP within the interpreter group is almost the same as within the Deaf group.

Interestingly, the study finds that variation within age-groups shows similar patterns for both the Deaf and the interpreter group in that older signers in both groups do not use AUX-OP as much as younger signers.
Moreover, this study also finds that the increase in the usage of AUX-OP within the youngest group of Deaf signers is to be attributed to an increased
use of double agreement constructions, in which AUX-OP is combined with another
agreement strategy.

In addition, based on the results of this study I propose that AUX-OP is not the sole agreement marker available in NGT. Rather, the findings of this study show that there are four different agreement markers available: AUX-OP, role-shifting, AUX and INDEX. Furthermore, I also propose that AUX-OP has two functions; namely as an agreement marker and as an emphatic marker.

The results of this study by Richard Cokart can be found in his MA thesis (2013).