What does a child understand about acceptable behavior at 18 months?

At 18 months, a child begins to grasp basic concepts of acceptable behavior through observation and imitation of adults and older children. They may understand simple rules such as "no" or "stop," especially when these are reinforced consistently. However, their understanding is still rudimentary, and they often act on impulse rather than a clear comprehension of social norms. Emotional responses, such as frustration or joy, can overshadow their understanding of acceptable behavior at this stage.