Welcome to Meerkat Academy. Admission is free, and lunch is provided, though the only thing on the menu is scorpions. While scorpions are tasty and nutritious, they are extremely dangerous. Just one mistake with an untrained eye or an overeager paw could mean death for an unlucky meerkat. So young meerkats have to attend eating classes.
Teaching – or, as psychologists call it, pedagogy – is defined as a kind of communication between two or more individuals that results in the transfer of knowledge or skills, according to Hungarian developmental psychologists Giorgy Gergely and Gergely Csibra. To qualify as teaching, the teacher must also modify his or her behaviour by tailoring lessons based on the performance of the student. And the knowledge transferred must be information that can be applied to new people, objects, locations, or events – what is known as generalisable information. To mutilate the oft-quoted idiom, showing a man where to find a fish is not teaching, but teaching a man how to find fish is.
Back in meerkat academy, experienced adults provide their students with dead scorpions that have already had their stingers removed. This way, the young can learn how to remove the edible parts. Once they've mastered that lesson, the adults provide dead scorpions with stingers still intact. It is much easier for the juveniles to learn to remove stingers from dead scorpions than ones that are alive and squirming. Finally, the adults provide the juveniles with living, lethal scorpions. In this way, the inexperienced pups learn to effectively interact with scorpions progressing from completely safe specimens to increasingly dangerous ones, according to their age and skills.
So, the adult meerkats adjust the curriculum – and, therefore, their own behaviour – based upon the behaviour of the juveniles. However, the adults never actually demonstrate proper scorpion-killing methods, they merely provide the materials. It would be like a culinary instructor who provided her students with pots, pans, knives, and ingredients, but no recipe. Instructors at the meerkat academy don't actually teach, at least according to the definition outlined by Gergely and Csibra.
Tandem-running ants may come closer. Like meerkats, when one ant knows the location of food, it explicitly modifies its behaviour so that the second ant can learn it as well. After leaving the nest, the demonstrator slows down or stops periodically so that the follower can memorise the route between the nest and the food source. If the process gets interrupted, the leader will wait for the learner to return before resuming the lesson. The way this works is that the knowledgeable ant takes the front position, and requires constant tapping on his rear end in order to continue demonstrating the path. The learner uses his antennae to tap the leader as if to say, "I'm paying attention, show me the way." While both meerkats and ants adjust their lessons based upon the behaviour of their students, only for ants is the interaction explicitly communicative and bidirectional.
However, this form of interaction among ants still doesn't fit the formal criteria for teaching. This is because the information that is transferred between the two ants is highly specific, and firmly situated within the here-and-now. Rather than showing each other how to find food more generally, the information provided is simply where food can be found at a specific moment in time. Many other animals instruct using this specific form of information flow. Bees display elaborate dances to indicate the location of food and monkeys use various calls to notify others of the presence of predators. A howler monkey that screams to inform others of an aerial predator can't communicate something like "aerial predators tend to hunt during the daytime," or "aerial predators come from the north." Cheetahs show their young how to stalk prey, which is general, but like meerkats, their interaction is not explicitly communicative.
In fact, every known teaching-like interaction among non-human animals involves only one specific kind of information transfer. Only human teaching fits all three criteria. And, more importantly, only humans are promiscuous teachers. Humans teach everything. Humans teach anything.