[lscharen]

This is similar the the (old) trick of adding a Uniform distribution component to a Mixture of Gaussians model. It doesn't really change the math wrt parameter optimization and probability evaluation, but provides a place to capture "background" or "unimportant" data points and improve the model robustness to outliers.

The motivation follows from the same problem the author points out in the original softmax formulation that it always "forces a choice" when it may be more useful to put a "Not Applicable" option into the model itself.

https://link.springer.com/article/10.1007/s10260-021-00578-2