Meta - Just Noticeable Distance is a measure for metacognitive sensitivity in tasks with psychometric functions.
It is similar in idea to the commonly used meta d' by Brian Maniscalco and Hakwan Lau (paper here: https://doi.org/10.1016/j.concog.2011.09.021; code here: http://www.columbia.edu/~bsm2105/type2sdt/). MetaJND can be seen as an extension of the meta-d' for tasks that use psychometric functions.
For a rationale and theoretical base of the metaJND measure please have a look at chapter 5 of my PhD thesis (freely available here: https://etheses.bham.ac.uk/id/eprint/9295/), where I used metaJND to show that 'multisensory integration boosts confidence and does not increase metacognitive noise'.
For questions and comments please write me on MeijerDavid1@gmail.com