̷ ̷ˈ ̷ ̷ ̷ ̷ˌmentə(r) noun
or ex·per·i·men·tor “, (ˌ) ̷ ̷ˌ ̷ ̷ ̷ ̷ˈmen.ˌtȯ(ə)r, -ȯ(ə)
( -s )
: one that experiments or conducts an experiment ; specifically : one that conducts an experiment in introspective psychology by arranging and determining the physical conditions of the observer's experience