Complex sentence: Leavens and Hopkins note that pointing behavior has been observed in captivity for a range of apes and monkeys, that much of this is spontaneous and occurs without explicit training to do so, and may be accompanied by visual monitoring of the person being interacted with.
Split into simpler sentences: Leavens and Hopkins note that pointing behavior has been observed in captivity for a range of species. It may be accompanied by visual monitoring of the person being interacted with.