In situations where a debt has both a higher interest rate and higher balance than another debt, the debt-snowball method will prioritize the smaller debt even though paying the larger debt would be more cost-effective. Several writers and researchers have considered this contradiction between the method and a strictly mathematical approach. Writing in Forbes, Rob Berger noted that "humans aren’t really rational creatures" and stresses that research tends to support the debt snowball method in real-world scenarios. The primary benefit of the smallest-balance plan is the psychological benefit of seeing results sooner, in that the debtor sees reductions in both the number of creditors owed (and, thus, the number of bills received) and the amounts owed to each creditor. In a 2012 study by Northwestern’s Kellogg School of Management, researchers found that "consumers who tackle small balances first are likelier to eliminate their overall debt" than trying to pay off high interest rate balances first. A 2016 study in Harvard Business Review came to a similar conclusion:
We tested a variety of hypotheses and ultimately determined that it is not the size of the repayment or how little is left on a card after a payment that has the biggest impact on people’s perception of progress; rather it’s what portion of the balance they succeed in paying off. Thus focusing on paying down the account with the smallest balance tends to have the most powerful effect on people’s sense of progress – and therefore their motivation to continue paying down their debts.
Author and radio host Dave Ramsey, a proponent of the debt-snowball method, concedes that an analysis of math and interest leans toward paying the highest interest debt first. However, based on his experience, Ramsey states that personal finance is "20 percent head knowledge and 80 percent behavior" and he argues that people trying to reduce debt need "quick wins" (i.e., paying off the smallest debt) in order to remain motivated toward debt reduction.
Research by Moty Amar and colleagues (2011) agreed that debtors are inclined to pay small debts first, which they attributed to "debt account aversion," the desire to reduce the number of outstanding debts regardless of balance or interest expense. However, they also found that when debtors are restricted from fully paying debts and are shown the interest that will accrue as a result of their choice, they make the mathematically optimal decision.