The impressive connections between mental processes such as perception, learning, memory, and reading and specific brain processes are evidence for the identification of mind and brain only if brain changes cause mental changes. But perhaps there is only correlation here rather than causation. The fact that ice cream consumption and drowning frequency are correlated does not show that one causes the other, as they have a common cause in high temperatures. A dualist could argue that all the empirical studies described above merely show that brain processes correlate with mental ones without brain's being the exclusive cause of mind. In scientific reasoning, the best way to show causation rather than mere correlation is to introduce an intervention, showing that manipulating one factor leads to a change in another factor. In psychology and neuroscience, there are both technical and ethical reasons why it is often hard to show that manipulating the brain can produce mental changes.