Yes i read that study, can't find it now though. It was from 2020 or 2021. There was a study with two groups, one group had the normal lidcombe programmet and the other had everything in lidcombe except the direct treatment. Both groups had the same success rate. Edit: They talked about the study on the stuttertalk podcast that was recommended, great podcast btw! There wasnt enough difference between the two groups to say that verbal contingencies made a difference.