When a person responds as if the worker has become stupid, that response is more about the organization than the worker in question
We must battle the need to believe that when a worker has some type of bad outcome, that adverse outcome happened because the worker became momentarily incompetent. Our thinking is driven by a bias toward bad things happening because someone did something bad. The bias that worker became stupid is really a strong force in how we learn from events. Thinking that the worker is stupid sends you down the wrong road for operational discovery.
If the worker was doing an excellent job on Tuesday, what changed so drastically so that this good worker now becomes a stupid worker on Wednesday?
If the employee was meeting production goals, behaving helpful to other people, and not being injured was that worker stupid before the event happened?