Answer: It may have been influenced by the fact he said he was making improvements and specifically stated he wasn't serving double-fault.
Explanation: There's a theory in psychology named 'self-fulfilling-prophecy'; it states that when someome is trying to avoid something at all cost, it then happens just because all the things that the person wasn't supponse to do, they did unconsciously.
In this case, Hebb was trying so hard to avoid double-faulting that he unconsciously prepared the scenario to fail.
