Answer:
Experimenter expectancy effect
Explanation:
The experimenter expectancy effect or observer expectancy effect postulates that when an experimenter is biased he can subconsciously influence the subjects in the experiment. Confirmation bias can now make the experimenter look for results that supports his bias.
This is evident in this instance where some students were given normal rats and told they were intelligent. The rats actually did better because the experimenters believed they were smarter than the other rats.