Several research studies have looked at the results of Johansen IAS. These have included single case studies, large scale studies and matched group studies.
Some of the most helpful studies have been individual case studies as there is a wide variation between individual profiles of difficulty and the different skills that benefit from improved listening.
Group studies have made use of pre- and post-intervention questionnaires, standardised tests of phonological processing and literacy and changes in behavioural audiograms towards the optimum hearing curve.