What contributes to biases

Cognitive biases can be caused by a number of different things, but it is these mental shortcuts, known as heuristics, that often play a major contributing role. ... Other factors that can also contribute to these biases: Emotions. Individual motivations. Limits on the mind's ability to process information.

Explanation:

faithful servants eumaeus and philaetius:

his ragged vest then drawn aside disclosed the sign conspicuous, and the scar exposed: eager they view'd, with joy they stood amazed with tearful eyes o'er all their master gazed:

these servants know ulysses by the scar he got when he was a child - so when he showed them the mark, they immediately knew this is truly their master and they hugged him, finally starting to believe his words.

the eye wink at the hand; yet let that be / which the eye fears, when it is done, to see.