Student or Learner
Does this "on three occasions " have to be "on the third occasion"? If not, what does it mean?
ex)A researcher study on captive Diana Monkeys suggests a capacity for empathy, long thought to be unique to humans. In the research, individual monkeys were trained to insert a token into a slot to obtain food. The oldest female in the group failed to learn how to do this. Her mate watched her unsuccessful attempts, and on three occasions he approached her, picked up the tokens, inserted them into the machine, and then allowed her to have the food.
Please be aware that I'm neither a native English speaker nor a teacher.