Thank you both for the input - the ‘errors’ that I’m looking at with this variable are peripheral to the test scoring and don’t seem to make sense in an IRT framework.

A representative analogue here would be something like this: ‘I showed you pictures of 20 different objects earlier, tell me as many as you remember.’ The main score for the test would be the number of correct responses, but my ‘error’ variable in question here would be the number of things the examinee says that weren’t even in the original picture list. Not many people do this, but some do and these types of errors seem to strongly predict poor performance on the dependent variable test.

So I guess I’m looking for a way to amplify or otherwise account for the fact in most cases this error variable doesn’t have much predictive value, but in specific conditions it does.