In 1960's studies of rats, scientists found that crowding increases the number of attacks among the animals significantly. But in recent experiments in which rhesus monkeys were placed in crowded conditions, although there was an increase in instances of "coping" behavior-such as submissive gestures and avoidance of dominant individuals-attacks did not become any more frequent. Therefore it is not likely that, for any species of monkey, crowding increases aggression as significantly as was seen in rats.

Which of the following, if true, most strengthens the argument?

【选项】Some individual monkeys in the experiment were involved in significantly more attacks than the other monkeys were.