Answer:
These words add humor to the text because they highlight the contrast between the demeanors of Twain and Bixby at this moment.
Step-by-step explanation:
The words contribute to Humor to the text as they highlight the contrast that exists between Twains and Bixby at present. The primary idea of the passage is that even if you are smart and practiced the same for an extended period when you are under pressure, you are likely to commit a mistake. Therefore it such scenarios in your level of experience will not matter. It happens viertally; you fail to see what you have seen before under similar situations. Therefore, it is a pressure blindness phenomenon.