Final answer:
Psychophysicists measure the absolute threshold when asking participants to indicate the detection of a stimulus with a "yes" or "no" response.
Step-by-step explanation:
When psychophysicists ask participants to answer "yes" or "no" regarding whether a stimulus was detected, they are measuring the absolute threshold. This measurement is concerned with the smallest level of stimulus intensity that a participant can detect 50% of the time. The just noticeable difference (jnd), also known as the difference threshold, is the minimal change in a stimulus that can still be reliably noticed by participants, but it does not relate to the detection of the stimulus presence itself. Finally, scaling of stimulus perception generally refers to methods like Stevens' Power Law, which involve rating the perceived intensity of stimulus rather than simply detecting its existence.