Which statement reflects a limitation of MRI/fMRI regarding causality?

• A. They cannot say anything about cause-effect relationships
• B. They can establish causality
• C. They measure neurotransmitter levels
• D. They reveal mental states

Answer: (A)

The main idea is that MRI and fMRI are correlational tools. They measure brain activity indirectly by tracking blood flow, producing a BOLD signal that shows which areas are active during a task. Because this activity is an association rather than a manipulation, you can see that a region is involved in a task but you cannot prove that activating that region causes the behavior. There could be other parts of the brain driving both the observed activity and the outcome, or the relationship could reflect the result of the behavior rather than its cause. The temporal resolution is relatively slow, and there’s a risk of reverse inference—inferring a mental process from a brain activation pattern—which further limits claims about causality. To establish causality, researchers would need direct manipulation or intervention (like brain stimulation or studying individuals with targeted brain lesions) to show that changing activity in a region changes the behavior. So the statement that captures this limitation is that MRI/fMRI cannot speak to cause-effect relationships. The other options overstate what these methods can do, since they do not measure neurotransmitter levels directly and do not reveal mental states in themselves.