悲观反应偏见（pessimistic response bias）的概念没查到，但根据文章的意思，当人或动物因环境影响而变得悲观的时候，会对某些事件产生不好的偏见。
bumped-out: 郁闷的，消极的
am'biguous: 不确定的
smirk: 假笑，傻笑
pellet: 小球
lever: 杠杆
novel: 新（奇）的
音频下载及链接：
3种语速的音频文件已上传百度云：链接| 密码: ez6k（在百度云点击MP3文件名可直接在线听）（原始语速来自A Moment of Science官网，1.5倍及2.0倍语速版本为我个人后期调整的）
本期文章原始音频、配图及文本均来自A Moment of Science官网：链接
文本：（参照源网页的文字、根据实际录音内容修改而成）：
Y: Hey, Don, you look all bumped-out.
D: Yaya, I'm having a worst day. I over-slept, and then had a flat tyre. And now Mike, the engineer, is smirking at me.
Y: No, he is not.
D: He is.
Y: Don, you're demonstrating what is known as pessimistic response bias. Because you’re anxious about other things, you assume that ambiguous events like Mike smile... (D: Smirk...) smiles can be negative too. And you are not alone. A study suggests that even rats exhibit similar behavior.
D: Rats can be pessimist?
Y: Apparently they can assume novel events are going to be positive or negative. You see, scientists trained rats to respond to two different tones. If they pressed a lever in response to one tone, they got a food pellet.
D: So that was the positive.
Y: And when they heard the other tone and pressed the lever, they heard an unpleasant noise—so here they learned not to press the lever to avoid a negative event.
D: Okay...
Y: Then scientists moved half the rats into housing conditions that changed unpredictably. For example, the cages were unfamiliar, or lights went on at unusual times. Then they tested the rats to see how they responded to a novel tone that fell between the positive and the negative tones. And guess what?
D: The rats from unstable environments were less likely to press the lever?
Y: Right. When the rats heard the novel tone they were less likely than the rats from the stable housing to associate the novel tone with food and press the lever. The next step, of course, is to study the brain processes involved here more thoroughly.
D: Wow, I feel better already. Now, where is my lever?
