Passage Summary: A psychologist claims that being an older or younger sibling doesn't change your actual personality, it just changes how your family sees you, because family reports show differences that professional tests don't find.

Conclusion: Birth order does not actually influence personality; it only influences how family members perceive a person's behavior.

Reasoning: Standard personality tests show no birth-order effects in adults, whereas reports from parents and siblings do show such effects.

Analysis: The psychologist is dismissing family reports as biased perceptions while treating standard personality tests as the objective truth. The 'Gap' in this argument is the assumption that these standard tests are actually capable of measuring birth-order effects if they existed. If the tests were simply not sensitive enough to detect these specific personality traits, the lack of results wouldn't prove that the effects don't exist. Look for an answer that validates the effectiveness of these standard personality tests in detecting birth-order influences.