The mirror-neuron system fires if the animate being perceives another being similar to itself either acting or suffering in specific ways that this system is tuned to. The effect is that, within these limits, the animate being feels prompted to act like its companion and feels affected by what affects its companion. Up to now, mirror-neuron subsystems have been found in primates including humans, less so in other mammals, and in birds.

The activity of the mirror-neuron system may underlie some kinds of emotional and cognitive abilities. Quite in general, the system facilitates understanding and learning. It is probably involved in the heightened degree of empathy observed in humans.

The mirror-neuron system is also active in the perception of meaningful gestures. Thus, the brain representation of the motor command triggering such gestures is stimulated when one sees them being executed (Arbib 2005). Consequently, the mirror-neuron system may have a function in speech perception as hypothesized by the motor theory of speech perception.

On the other hand, there is an internal feedback loop in speech production: the speaker utters his message, he has proprioception of his articulation and he hears his own product, comparing it with what he intended to say.

In 2024, there is consensus that the neural system does show such mirroring behavior (Bonini et al. 2022). In human beings, this replicating behavior may develop at an infant age. At the same time, it is not clear that there are special cells in some brain area responsible for motor control which are dedicated to the mirroring behavior and therefore could be identified as mirror neurons. Instead, the mirroring phenomenon may be due to spreading activation across different brain areas.