A researcher wanted to investigate whether a citrus scent affects concentration during a reading comprehension task.

The researcher conducted a study using 12 student volunteers from a university. The researcher used a repeated measures design. Half of the participants completed the task first in Condition A (citrus scent present) and the other half in Condition B (no scent present).

All participants were asked to read a 1000-word academic text and answer a 10-item comprehension test as quickly as possible inside a soundproof cubicle in the university's psychology department. Standardised instructions were read to all participants, and the room temperature was kept constant at 21°C. The researcher recorded their comprehension scores. The participants returned to the laboratory three days later to complete the alternate condition with an equivalent reading text.

Identify the type of experiment used in this study.