Which psychophysicist's major contribution was to demonstrate that the relationship between incoming stimuli and corresponding perceptions was not one-to-one?

The psycho-physicist we are talking about here is Fechner.

Thus,

the answer is none other than Gustav Fechner.

Gustav Theodor Fechner was indeed the founder of the experimental psychology. This experimental psychology is the one that applied the scientific method to the research of behavior and mind. And the question above is also one of the contributions of Gustav Fechner and his works.

answer; the population in brazil is very diverse there are many races and ethnic groups

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.