Human Uniqueness. Human Uniqueness. Why are we so different? 12/6/2017. Four Candidates

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1 Our Hominid Ancestors In humans, brain tissue has more than doubled over the past 2 million years. Break from chimps 3-5 million Our Hominid Ancestors Our Hominid Ancestors Relative Brain Size in Our Ancestors Compared to Modern Apes Australopithecus afarensis million years ago Homo habilis million years ago Homo erectus million years ago Homo neanderthalensis 600K-350K years ago Homo sapiens 200K years ago Estimate of Brain Size Body Size Why are we so different? 1) (tools and physical reasoning) 2) (social) 3) (communication) 4) (abstract reasoning) 1

2 12/6/2017 Thoughts don t fossilize There is a little bit of direct evidence Chauvet cave, France 35,000 years ago, symbolic & religious art Untouched footprints of humans and extinct animals. The next best thing What can modern animals tell us about an extinct human? 12 million Clues about what humans were like at our last common ancestor with modern primate. Look at our closest living ancestors (modern primates) 3-5 million 35 million 1) (tools and innovations) 2) 3) 4) 2

3 12/6/2017 We can infer that our common ancestor with chimpanzees had the ability to use simple tools. 2.5 million years ago Homo habilis Humans obviously went well beyond simple tools. A little meat A lot of meat Bipedalism (4 million) Freed hands to carry and throw things Chimpanzees Homo Habilis 2.3 million Allowed us to travel long distances on less energy Homo habilis 2.3 million Homo erectus 1.8 million Tool Use Physical cognition for making and using tools Quality diet (processing foods, hunting) Cooperation: to hunt in groups Sharing: to distribute food : to cooperate Teaching: to learn faster Homo neanderthalensis 600,000 3

4 1) (tools and innovations) 2) 3) 4) Shared intentionality: When two people look at the same thing (a reference point) and they know they are looking at the same thing. In humans, when people are looking at the same thing, they usually talk about it or act on it (they have a goal). Human infants can share a visual reference with adults by following gaze, pointing, and looking back and forth. Other animals aren t known to communicate in this way. Shared intentionality means sharing a reference point and a goal. Each dot is a different Order of mammals. Social Demands Whales, dolphins Primates Proportion of Stable Groups Horses, rhinos, tapirs Camels, pigs, deer, hippos, cows, sheep Cats, canids, bears, raccoons, seals Shrews, moles, hedgehogs Primates interact in triads, not just dyads. Brain Size Primates form large stable groups. The size of the cortex is correlated with average group size across species. Human social networks are exceptionally large: about 100 people Chimp Human 4

5 Chimpanzees have gaze following. Apes do not point and they don t understand pointing. Other animals (eg., dogs) can understand our pointing but they never use pointing or gesturing to show something to us (or to each other). But humans have: theory of mind, pointing, cooperation, helping, and teaching on top of that. Humans Chimpanzees can cooperate if necessary but don t share. Bonobos can cooperate and share the food (prosocial). Choose One: Cooperate Option Solo Option Chimps Mind reading or, thinking about the thoughts of others. BUT, given a choice between cooperating and going solo, apesprefer to go solo whereas human childrenprefer to cooperate. What s the difference between a human child and a chimpanzee? 100 chimpanzees vs year-old children Same physical and social cognition tests for both groups Physical tests: Spatial Memory Object Permanence Quantities Tool Use Social tests: Social learning Following pointing Gesturing Gaze following Goal inferring These are all the physical and social cognition tests. 5

6 Physical Social Human children only differed from apes in social tests. Performance on the physical tests was high and equal. Shared reference point Shared goals Cooperation Teaching 1) (tools and innovations) 2) 3) 4) When animals engage in human-like behaviors, they are usually applied only to one type of thing: Episodic memory in scrub jays (food caching) Gaze tracking in chimpanzees (stealing food) Teaching in meerkats (prey handling) Imitation in parrots (songs, sounds) Humans on the other hand use episodic memory, gaze tracking, imitation, and teaching for many types of information: Episodic memory (meals, social exchanges, object use, etc, etc, etc) Gaze tracking (helping, communicating, stealing, playing, etc, etc) Teaching & Imitation (food, object use, language, social etc, etc) allows humans to bring many types of information together for thought and communication. 6

7 Thoughts Episodic Memory Gaze Following Teaching Imitation Navigation effects thought Recursion The wolf ate the dog. The wolf ate the dog who ate the dog. The wolf ate the dog who ate the dog who ate the dog. is generative Food Objects and Tools Paul saw the wolf who ate the dog who ate the dog who ate the dog. On his way back from the store, Paul saw the wolf who ate the dog who ate the dog who ate the dog. On his way back from the store, Paul saw the wolf who ate the dog who ate the dog who ate the dog but I don t want to talk about that right now. Social behaviors Human language connects many types of information. So, our thoughts operate on many types of information. On his way back from the store, Paul saw the wolf who ate the dog who ate the dog who ate the dog but I don t want to talk about that right now because I m really sad..can go on infinitely (open-ended) and can keep adding clauses to clauses (recursive) to get new meanings. is generative Colorless green ideas sleep furiously. Even though this sentence is bizarre and probably never heard before, people can still get some kind of meaning out of it. In ape language studies, apes had difficulty producing long utterances and they often reproduced old statements not new ideas. Animal communication isn t like that. The open structure of human language facilitates new ideas. allows many types of information to be brought together. has generative grammar which allows new ideas to be created. 1) (tools and innovations) 2) 3) 4) Non-human animals reason about the things they can see (or sense) directly. Humans go beyond Example: Which two go together? Not Directly Observable Directly Observable Humans say that the birds go together. Chimpanzees would choose the perceptually similar animals. 7

8 Relational reasoning is understanding an abstract relationship between entities. Analogical Reasoning Logical Rules Causal Relations Theory of Mind Animals show some success on these relational tasks. Humans use these abilities routinely. Causal Apes & monkeys fail to infer the causal relation between pushing the object and the trap over 100 trials. 3-year-old human children solve this within a few trials. Analogical Primates do not easily reason about patterns. Only 1 non-human subject ever shown to solve analogical relations after training. 3-year-old human children solve these tasks. Humans Patterns and abstract relations cannot be directly observed. Theory of Mind Relation between what a person sees and what they think. Chimps You have to arrive at a pattern or relation through abstract reasoning in your mind. Non-human primates primarily think about things they can directly observe. Humans think about abstract patterns and relations. Abstract set the stage for: Causal Reasoning (Tool Use) Theory of Mind (Social Cognition) 1) Tools, hunting, bipedalism, meat 2) shared references & goals, theory of mind, cooperation, teaching 3) Bridging types of information, communicating novel ideas 4) Patterns, abstract rules, relations 8

9 12/6/2017 Final Exam EXAM is Monday, normal time & place It is not cumulative. 9