Question

Dr. Shill conducted a study in which she administered morphine, which mimics the action of naturally occurring endorphins, to volunteers in hopes of determining whether morphine boosts mood. In this instance, the independent variable is a(n)

a
Antagonist
b
Synapse
c
Ion
d
Agonist

Answer 1

In this study, morphine is acting as a substance that mimics the action of endorphins, which are naturally occurring neurotransmitters that promote feelings of pleasure and pain relief. In this context, morphine is functioning as an **agonist**, which means it enhances or increases the action of the naturally occurring substance.

Therefore, the correct answer is:

**d. Agonist**