“…We anticipated that ISS-5 could be more effective for some learners based on prior research suggesting this as a plausible set size (Haegele & Burns, 2015), based on the increase in the number of learning trials per relationship, based on prior studies demonstrating advantages of smaller learning sets (Shaughnessy, 1973), and the lower cognitive load created by the smaller set (Cheng, Lu, & Yang, 2015). We anticipated that ISS-20 could be more effective for some learners based on prior research suggesting that under some conditions, higher cognitive load is more effective (Crossley et al, 2018; Phan et al, 2017), that devoting time to rehearsing known relations is less efficient (Cates et al, 2003), that CTD can be efficient in teaching a large set of responses (Mattingly & Bott, 1990), that when learning sets are too small they can result in participants learning a lower percentage of the targets (Burns et al, 2015), and based on concerns that repetitive rehearsal of a small learning set may undermine student attention and motivation. Thus, our central research questions were, would ISS be associated with differentiation in responding, and would differentiation vary across participants?…”