[season 01 episode 17]

Leonard: She does not want to talk.
Sheldon: Not surprising. Penny’s emotional response is originated in the primitive portion of the brain, known as the amygdala. While speech is centered in the much more recently developed new-cortex.
Sheldon: The former can easily overpower the latter, Giving scientific credence to the notion of being “rendered speechless”.
Leonard: …
[Leonard is rendered speechless]
Sheldon: Or maybe she just doesn’t want to talk.

Leonard: 她不想说话。
Sheldon: 这不奇怪。Penny的情感反应源自于大脑最原始的部分，即所谓的杏仁体。而言语能力则处于后进演化的新脑皮层的中心地带。
Sheldon: 前者可以轻易地统治后者。这也正是通常所说的“哑口无言”这一表达的的科学证据。
Leonard: 。。。
[Leonard 哑口无言]
Sheldon: 也可能只是她不想说话罢了。