Amind-altering substance that changes the brain's neurochmistry by activating neurotransmitter receptors is called a :
a. psychoendorphin
b. pssychoactive drug
c. nuromoulator
d. neurotoxin

What makes the yardstick test a direct measurement of reaction time? a. the further the yardstick falls, the slower the reaction time. b. yardsticks have numerical markings for length. c. yardsticks are designed to measure reaction time. d. all of the above select the best answer from the choices provided.