Bennett explicitly states at the beginning of this book that his discussion only details the path to intelligence that humans, specifically, took through the evolutionary process. That said, in his explanations, he references the commonalities that primates, mammals, vertebrates, and multi-celled creatures, etc shared with human development, when appropriate. “Breakthrough #1 was steering: the breakthrough of navigating by categorizing stimuli into good and bad, and turning toward good things and away from bad things. Six hundred million years ago, radially symmetric neuron-enabled coral-like animals reformed into animals with a bilateral body. These bilateral body plans simplified navigational decisions into binary turning choices….
Breakthrough #2 was reinforcing: the breakthrough of learning to repeat behaviors that historically have led to positive valence and inhibit behaviors that have led to negative valence…. Brains formed into the basic template of all modern vertebrates: the cortex to recognize patterns and build spatial maps and the basal ganglia to learn by trial and error. And both were built on top of the more ancient vestiges of valence machinery housed in the hypothalamus…. While trial and error does not explain all of animal learning, it undergirds a surprisingly large portion of it…. To solve the temporal credit assignment problem, brains must reinforce behaviors based on changes in predicted future rewards, not actual rewards. This is why animals get addicted to dopamine-releasing behaviors despite it not being pleasurable, and this is why dopamine responses quickly shift their activations to the moments when animals predict upcoming reward and away from rewards themselves…. Both disappointment and relief are emergent properties of a brain designed to learn by predicting future rewards…. In the brain, the result was the vertebrate cortex, which somehow recognizes patterns without supervision, somehow accurately discriminates overlapping patterns and generalizes patterns to new experiences, somehow continually learns patterns without suffering from catastrophic forgetting, and somehow recognizes patterns despite large variance in its input…. It is also not a coincidence that pattern recognition and reinforcement learning evolved simultaneously in evolution….
Breakthrough #3 was simulating: the breakthrough of mentally simulating stimuli and actions…. [The] neocortex enabled animals to internally render a simulation of reality. This enabled them to vicariously show the basal ganglia what to do before the animal actually did anything. This was learning by imagining. These animals developed the ability to plan. This enabled these small mammals to re-render past events (episodic memory) and consider alternative past choices (counterfactual learning)…. If you have a rich enough inner model of the external world, you can explore that world in your mind and predict the consequences of actions you have never taken…. It is when the simulation in your neocortex becomes decoupled from the real external world around you—when it imagines things that are not there—that its power becomes most evident…. Habits are automated actions triggered by stimuli directly (they are model-free). They are behaviors controlled directly by the basal ganglia. They are the way mammalian brains save time and energy, avoiding unnecessarily engaging in simulation and planning…. Humans and, indeed, all mammals (and some other animals that independently evolved simulation) sometimes pause to simulate their options (model-based, goal-driven, system 2) and sometimes act automatically (model-free, habitual, system 1)….
Breakthrough #4 was mentalizing: the breakthrough of modeling ones own mind…. This in effect, meant that these primates could simulate not only actions and stimuli (like early mammals), but also their own mental states with differing intent and knowledge…. The bigger the neocortex of a primate, the bigger its social group…. Animals who fell into the strategy of group living evolved tools to resolve disputes while minimizing the energetic cost of such disputes. This led to the development of mechanisms to signal strength and submission without having to actually engage in a physical altercation…. Understanding the minds of others requires understanding not only their intentions but also their knowledge…. The best evidence for social projection theory is the fact that tasks that require understanding yourself and tasks that require understanding others both activate and require the same uniquely primate neural structures…. When a primate watches another primate do an action. its premotor cortex often mirrors the actions it is observing…. Teaching requires understanding what another mind does not know and what demonstrations would help manipulate another mind’s knowledge in the correct way…. Understanding the intentions of movements is essential for observational learning to work; it enables us to filter out extraneous movements and extract the essence of a skill…. Both theory of mind and anticipating future needs are present, even in a primitive form, in primates, but not in many other mammals….
Breakthrough #5 was speaking: the breakthrough of naming and grammar, of tethering our inner simulations together to enable the accumulation of thoughts across generations…. First, humans evolved bigger brains…. Second, humans became more specialized within their groups…. Third, population sizes expanded…. And fourth, most recent and most important, we invented writing. Writing allows humans to have a collective memory of ideas that can be downloaded at will and that contain effectively an infinite corpus of knowledge…. We synchronize our inner simulations, turning human cultures into a kind of meta-life-form whose consciousness is instantiated within the persistent ideas and thoughts flowing through millions of human brains over generations…. The emergence from language was as monumental an event as the emergence of the first self-replicating DNA molecules. Language transformed the human brain from an ephemeral organ to an eternal medium of accumulating inventions.”
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