Identifying Confirmation Bias in Research

In the field of psychology, cognitive biases are systematic patterns of deviation from norm or rationality in judgment, whereby inferences about other people and situations may be drawn in an illogical fashion. One well-known cognitive bias is the confirmation bias, which can alter the way individuals perceive information and obtain evidence. Consider the following scenario:

A researcher is conducting an experiment to assess the effectiveness of a new medication for anxiety. They initially believe the drug is effective and, as a result, pay more attention to any positive outcomes reported by participants while ignoring or downplaying any negative or inconclusive results. This selective gathering of evidence conforms to their initial belief.

Based on this scenario, which cognitive bias is most prominently displayed by the researcher?