L&C Lecture 2 - Primate Communication

• Last common ancestor (LCA) between chimpanzees, bonobos, and humans existed 5-7 million years ago.
• Humans did not evolve from chimpanzees and bonobos; they share a LCA.

Why Study Primate Communication?

• Language doesn't fossilize, so studying primate communication helps understand the roots of language.
• It provides a window into our primate past.
• It helps understand the principle of homology.

How Did Language Evolve?

• Language may have evolved through a vocal route.
• Language may have evolved through a gestural route.
• Language may have evolved through a combination of both vocal and gestural routes.

Communicative Flexibility: Vocal Learning

• Humans are excellent vocal learners and can learn to produce new sounds and vocally imitate.
• Vocal imitation underpins language learning.
• Whales and birds also demonstrate impressive vocal learning abilities, with elaborate vocal cultures and dialects.

Primates and Vocal Learning

• Primates have remarkably limited capacities for vocal learning.
• Gestures can be readily learned and invented.
• Chimpanzees from a zoo in the Netherlands were transferred to join the Edinburgh chimps in 2011, per the Watson et al. (2015) study conducted at the Edinburgh Zoo.
• The study tracked the two groups’ social networks and their food grunts for apples over three years.
• Over three years, the two groups became more integrated, and the Dutch chimps’ food calls became more similar to the Edinburgh ones.
• Chimps may have some control over vocalizations, though there is not much evidence to demonstrate this.

Referential Communication

• Some vocalizations provide meaning about the world, instead of communicating emotions.
• Signals that refer to objects/events in the world are considered an early form of semantic communication.

Playback Experiments

• Playback experiments play sounds to animals to observe their reactions.
• These experiments explore the information that sounds convey to receivers.

Referential Alarm Calls

• Playback studies by Robert Seyfarth & Dorothy Cheney found that Vervet monkeys in Kenya use different alarm calls for different predators.
• "Run for cover!" is used when a leopard is seen.
• "Look up!" is used when an eagle is seen.
• "Scan the grass!" is used when a snake is seen.

The Evolution of Syntax

• The order of linguistic elements influences their meaning.
• For example, the letters ARE, EAR, and ERA have different meanings based on the order.
• The order of calls changing their meaning is currently being explored.

Call Sequences: Basic Form of Syntax?

• Putty-nosed monkeys use "hacks" and "pyows" in call sequences.
• The different call sequences may refer to different predators or travel.

Bonobo Food-Call Sequences

• Bonobos have different food calls, including barks, peeps, peep-yelps, yelps, and grunts, to describe different types of food.

Bonobo Food Call Sequences with Playback Experiments

• Bonobo foraging behavior differs depending on the food call they hear.
• Bonobos respond according to whether they hear a kiwi site or an apple site call.

Audience Effects & Intentionality

• Chimpanzees inform their friends about the presence of food, which demonstrates intentionality.
• Slocombe et al. (2010) found that chimpanzees inform others about food presence and show audience effects.
• Chimpanzees inform each other about potential danger, as demonstrated by a fake snake study in Uganda.
• Crockford et al. (2012) found that chimpanzees inform ignorant group members about danger, which makes them more likely to engage in alarm calls.

Ape Gestures

• A gesture is a discrete, mechanically ineffective body movement used to communicate intentionally to change the behavior of the receiver.
• Ape gestures are more flexible than vocalizations.

More on Ape Gestures

• These gestures are produced flexibly across many contexts.
• Gestures can be learned, modified, and invented.
• Gestures show intentional control.
• Some gestures have specific meanings.
• Wild chimpanzees use 66 gestures to intentionally communicate 19 meanings (Hobaiter & Byrne 2014).
• Graham, et al. (2018) found that Bonobo and chimpanzee gestures overlap extensively in meaning.

Summary

• Aspects of language are deeply rooted in our primate past.
• Studying primates can help estimate our abilities before humans.
• Primate vocalizations can convey meaningful information, which is called referential communication.
• Primates can combine calls into meaningful sequences, which is syntax.
• Primates adjust their calling according to their audience, which is intentional communication.
• Primate vocalizations and gestures offer insights into language evolution.