2.4.1 Odor familiarity survey
The familiarity of 121 odors was investigated in 100 volunteers (aged
18–65 years). Based on Niklassen et al.’s study22, we
developed an odor familiarity questionnaire co-ntaining 121 kinds of
odors. The questionnaire included basic information of the volunte-ers:
name, gender, age, contact details, and occupation (strict measures were
taken to ens-ure that the privacy and personally identifiable
information of volunteers were not expos-ed during the research process,
and the names of volunteers were hidden and replaced by numbers only).
According to the familiarity with the 121 common odors provided in the
questionnaire, we used a Likert-type scale for the volunteers to score
using an online or paper questionnaire (the content of the online and
paper questionnaires were similar). T-he scale ranged from 1 to 5, for
which 1 is not familiar, and 5 is highly familiar. If the v-olunteers
scored 4 or 5 on an odor, they were considered ”familiar” with the odor.
The n-umber of ”familiar” volunteers with an odor among 100 volunteers
was the final familia-rity score of the odor.