several years ago, fidget spinners experienced a brief window of popularity. The fad did not last but, at the time, some suggested that fidget spinners could improve retention by giving learners something concrete to do with their hands. Soares and Storm (2020) tested the efficacy of fidget spinners for improving retention.¹They had college students watch two educational videos; after each video, students' memory for the videos was measured. For one video, participants used a fidget spinner; for the other, they did not. Soares and Storm counterbalanced the use of the fidget spinner, such that half of the participants used the fidget spinner for the first video but not thesecond video, and the other half of the participants used the fidget spinner for the second video but not the first video. Results showed that, contrary to popular belief, fidget spinners actually harmed memory, with participants remembering significantly more of the video for which they did not use the fidget spinner.

a. Did Soares and Storm (2020) use an experimental or quasi-experimental design? Explain your answer.