Final answer:
Participants' recognition thresholds are lower for frequently seen words due to priming.
Step-by-step explanation:
The participants' recognition thresholds are lower for frequently seen words because of priming. Priming is a type of implicit memory where exposure to a stimulus affects the response to a later stimulus. In the case of frequently seen words, the participants are likely to have been exposed to them before, which makes it easier for them to recognize and remember the words.