Are you sure that the bias went unnoticed? The article says "most participants in their experiments only started to notice bias when the AI showed biased perfor

Are you sure that the bias went unnoticed? The article says "most participants in their experiments only started to notice bias when the AI showed biased performance", which I understand to mean they noticed the bias in the experiment you're talking about. Have I got that wrong? Is it written wrong? Do we even have the means to check?