A three-dimensional magnetic resonance image of a macaque monkey head. Inset: A schematic of the combination of cortical field maps of tactile stimulation obtained using fMRI (red and green squares) and electrophysiological recording techniques (cross-hatched regions).

Functional magnetic resonance imaging (fMRI) experiments are, no doubt, incredibly intriguing: Researchers put volunteers inside a huge, harmless magnet that takes detailed pictures of the brain, expose those people to some sort of sensory stimulus, see what regions of the brain light up, and try to draw some conclusions about brain activity. Such experiments have become increasingly popular in neuroscience and psychology since their advent in the early 1990s. They are more commonplace for basic research studies than costly, time-consuming experiments done with positron emission tomography (PET). Magnetic resonance machines have been used in everything from psychiatry studies investigating how the brain reacts as food is digested to social psychology studies asking how the...