How did Neha Mahajan and her research team measure whether rhesus monkeys distinguished between ingroup and outgroup rhesus monkeys?

1. How did Neha Mahajan and her research team measure whether rhesus monkeys distinguished between ingroup and outgroup rhesus monkeys?

With regard to this question, what did they find?

What explanation did they give for these results? In other words, what did these results suggest?

What was a potential alternative explanation for their results?

What did they do to figure out which of these two potential explanations was correct? By two explanations I am referring to your answers to questions b and c.

With regard to this last question, what did they find?

2. Mahajan and her team also tried to figure out whether monkeys had negative feelings toward outgroup monkeys.