Effects of extending the one-more-than technique with the support of a mobile purchasing assistance system.

Hsu et al. (2014) asked three high-school students with intellectual disability to buy snacks priced higher than they could count. The team loaded a free app on each teen's own phone. The app showed a picture of the item plus one extra dot. Students learned to hand the cashier "one more" dollar than the dots shown.

The researchers used a multiple-baseline design. They started the app training in a school store, then moved to two real community shops. They tracked if the teens could still buy items eight weeks later without the phone.

All three students could buy items that cost more than they could count. They kept the skill for eight weeks. They also used the trick in new stores they had never visited.

No adult prompts were needed after the first three shopping trips. The teens simply looked at the phone, counted the dots, and handed over "one more" bill.

Dong et al. (2025) took the same phone idea but swapped the task. Their teens with autism used a picture schedule to run the self-checkout instead of paying a cashier. Both studies show that a personal phone can replace bulky cards or binders in real stores.

Charlop et al. (1990) did the job with paper. Adults with mild ID mastered checkbooks through a self-paced booklet. Guo-Liang moves that self-paced idea onto a screen teens already carry.

Lancioni et al. (2000) used a clunky portable computer to give picture prompts. The 2014 study trims the hardware down to a phone and adds the clever "one-more" rule so students don't need to count exact prices.

If a client can count to five but wants to buy a four-dollar smoothie, you no longer need to pre-teach every price. Load the free one-more-than app, snap one photo of the item, and send them into line. The skill lasts two months and works in any store. That single tool can open grocery, pharmacy, and food-court aisles that were previously off-limits because of tricky price tags.