Work History / Professional Experience Section of US Grad School Application - Listing Research Internships
List them anywhere reasonable rather than not listing them at all. Probably you can give short descriptions so that there is no misunderstanding. 

But let the reader judge the significance rather than assuming that they aren't worth listing. Err on the "say more" side rather than "say less". 

And, if you can send a Statement of Purpose, mention there how those things support the sort of thing you want to do.