The experience of feeling like the author of your own actions, where you cause things to happen in the world, is known as the sense of agency. This fundamental feeling allows you to perceive yourself as an active participant rather than a passive observer. For instance, when you type a sentence on a keyboard, the sensation of your fingers moving and the words appearing on the screen are seamlessly linked to your intention, creating a feeling of control.
The Core Components of Agency
The sense of agency is more than simply performing a voluntary action; it is the subjective feeling of being in control of that action. It represents the implicit, pre-reflective awareness that you are the initiator and controller of your own volitional movements and their outcomes. This feeling of authorship distinguishes self-generated actions from those caused by external forces or other individuals.
It is important to differentiate the sense of agency from the “sense of ownership.” The sense of ownership is the feeling that a body part, thought, or sensation belongs to you. For example, if a doctor lifts your arm, you still feel that the arm is yours (sense of ownership), but you do not feel that you are controlling the movement (lack of sense of agency). When you choose to lift your own arm, both the sense of ownership and the sense of agency are typically present and tightly integrated.
The Brain’s Predictive Mechanism
The brain generates this feeling of agency through a sophisticated process often described by the “forward model” theory. When you decide to perform an action, your brain sends a motor command to the muscles involved. Simultaneously, an “efference copy” of this motor command is created and sent to internal predictive models within the brain.
These internal models use the efference copy to generate a prediction of the sensory consequences of the intended action before it actually occurs. This prediction includes the expected timing, direction, and various sensory feedback such as tactile, proprioceptive, and auditory sensations. For example, when reaching for a cup, your brain predicts how your hand will feel as it moves through space and when it will make contact.
The brain then continuously compares this predicted sensory feedback with the actual sensory information received from the body and the environment as the action unfolds. If there is a close match between the prediction and the actual sensory input, a strong sense of agency is generated. This match signals that the action is proceeding as intended and is indeed self-generated.
Conversely, a mismatch between the predicted and actual sensory feedback, known as a “prediction error,” weakens or diminishes the sense of agency. This discrepancy indicates that the action’s outcome was not what was expected, suggesting a lack of full control or an external influence. Brain regions within the parietal cortex, such as the temporo-parietal junction (TPJ) and inferior parietal lobule (IPL), play a significant role in detecting these mismatches and are particularly active when a sense of non-agency is experienced. Other areas, including the cerebellum, are also involved in generating the implicit feeling of agency.
Development and External Influences
The sense of agency is not innate but develops and is refined through interaction with the environment. Infants begin to develop this sense by learning cause-and-effect relationships from their movements and the resulting sensory feedback. For example, an infant shaking a rattle learns that their movement directly produces a sound, thus recognizing their own efficacy in causing an external event.
As individuals grow, various external factors can modulate their sense of agency. Using tools, such as a hammer or a car, can extend one’s perceived agency beyond the physical body. The tool becomes an extension of the self, allowing the user to feel control over actions performed through it. This happens because the brain integrates the tool’s effects into its predictive models, associating the user’s intentions with the tool’s outcomes.
Conversely, social contexts can significantly diminish the sense of agency. When individuals act under coercion or direct orders, their subjective feeling of being the author of their actions can be reduced. This suggests that both the person receiving and, to some extent, the person giving coercive orders may experience a reduced sense of agency for the action’s effect.
Impaired Sense of Agency in Clinical Conditions
Disruptions to the sense of agency can have profound effects, leading to altered perceptions of self and reality in various clinical conditions. One prominent example is schizophrenia, where patients may experience “delusions of control” or “delusions of influence”. In these instances, individuals may feel that external forces are controlling their actions, thoughts, or emotions, even though they are performing the actions themselves.
This phenomenon is often linked to a failure in the brain’s predictive mechanism. The forward model, which normally predicts the sensory consequences of self-generated actions, may not function correctly in schizophrenia. This deficit can lead to a mismatch where the brain fails to predict the sensory feedback of its own motor commands, making self-generated movements feel as if they are passively initiated or controlled by an outside entity.
Another condition illustrating a breakdown in agency is anarchic hand syndrome. Individuals with this neurological disorder experience one of their hands performing complex, goal-directed movements without their conscious intention or control. Despite the hand acting seemingly on its own, the person still recognizes it as belonging to their body (maintaining a sense of ownership). This disorder exemplifies a clear dissociation where the sense of ownership is preserved, but the sense of agency is lost. This is believed to occur due to damage in brain areas involved in motor planning and inhibition, such as the supplementary motor area or corpus callosum, leading to actions that are executed without the brain’s internal prediction of self-authorship.