Some Investigators Claim They Have Taught Monkeys to Understand Spoken

Multiple Choice

Some investigators claim they have taught monkeys to understand spoken English, but another scientist argues that the results might be due to a Clever Hans effect. What does this mean?

A) The procedure works only if training begins during infancy.
B) The procedure works only with a few carefully selected and especially bright individuals.
C) The monkeys might be responding to subtle visual cues accidentally given by the investigators.
D) The results are not replicable.