Final answer:
The common aspect of all natural reinforcers is the release of dopamine within the nucleus accumbens, a key part of the brain's reward system that motivates repetition of behaviors leading to this positive reinforcement.
Step-by-step explanation:
The common aspect of all natural reinforcers relates to the release of dopamine within the nucleus accumbens. The nucleus accumbens is a central area in the brain's reward system, heavily influenced by dopaminergic signals from the ventral tegmental area (VTA). When a natural reinforcer is experienced, such as food, social interactions, or sexual activity, dopamine is released in the nucleus accumbens, which contributes to the feeling of pleasure and drives the motivation to repeat the behavior that led to this positive reinforcement.
Moreover, dopaminergic pathways, including the mesolimbic pathway, play crucial roles in not only the pleasure and reward but also in the regulation of movement and mediation of addiction. This is because dopamine release and the subsequent activation of dopamine receptors in the brain's reward circuitry are fundamental for reinforcing behaviors necessary for survival, hence the classification as natural reinforcers.