# Decrease in d' with concurrent increase of criterion

I was reading about an experimental condition where subjects d' (sensitivity) decreases, while at the same time their criterion is increasing (a shift to the right). The authors were arguing with a decrease in the hit rates.

I was wondering how this is possible: An increase of criterion should decrease hit rates as well as false alarm rates (the subject becomes more conservative). As these are both proportionally decreased, sensitivity, defined as

$$𝑑′=𝑍_𝐷−𝑍_𝐹$$

should remain constant, or not?