Answer:Confirmation bias
Explanation:
Confirmation bias occurs when we favour information that confirms what we already believe.
Confirmation biases affect how we search for information as well as how we interpret it or remember it. We tend to ignore or not pay attention to any information that seems to contradict with what we believe until we find that which confirms. Even when we recall Information it becomes easier to recall Information when we see something that confirms our own existing beliefs.
Diego couldn't notice Farrah' s good behaviour because his mind is already fixated on what he already believes about her and only when that is confirmed he then starts to notice her behaviour.