One of these creatures performed the "masking task" after learning how to match Arabic numerals to objects bearing the corresponding numbers.
One of these creatures performed the "masking task" after learning how to match Arabic numerals to objects bearing the corresponding numbers. These creatures formed male-only "border patrols" to kill individuals who wandered off from the main group. Some of these creatures stacked boxes to reach food in an experiment designed by (*) Wolfgang Kohler. At Columbia University, Herbert Terrace taught American Sign Language to one of these creatures, who was given a name punning on "Noam Chomsky." Another scientist observed them using stalks of grass to dislodge termites from mounds, disproving the notion that only humans could use tools. For 10 points, name these primates studied extensively by Jane Goodall.  
One of these creatures performed the "masking task" after learning how to match Arabic numerals to objects bearing the corresponding numbers.
common chimpanzees [or Pan troglodytes; prompt on primates until mentioned; prompt on monkeys; prompt on apes; in case anyone's curious, the chimp's name was "Nim Chimpsky"]