How The Mind Works

Chapter 5 focuses on human reasoning and starts by introducing Darwin and Wallace. These two scientists independently arrived at natural selection as how species evolve, but where Darwin saw no problems with the human brain (and mind) evolving through natural selection, Wallace found the issue to be a sticking point. He argued that foragers and those in non-industrial civilizations would not need a very large or complex brain. Therefore, once we were foragers, human intelligence should have stagnated and not reached the level it has reached in modern humans.

Like many arguments against the human brain evolving, Wallace’s contention doesn’t consider the basic tenet of natural selection: It does not have a goal. Scientific thinking is slow and methodical, which could be a problem when needing to make quick decisions. Heuristics and knowledge of the current situation are more highly valued in some environments, and that doesn’t mean that the brain required to handle that thinking is any less complex or advanced than a brain molded for scientific thinking. Each person’s brain is shaped by the environment of the brains that came before it and its own environment to maximize skills needed for survival in that environment.

One common thread in human thinking is categorizing. Theories of why we categorize information tend to fall short of a true reason because they don’t address a survival need. Just because categories could reduce the load of storing information doesn’t mean we need to make them and that there would be a survival pressure to do so. Instead, categories are useful because they let us quickly assign properties to new information without needing to learn all the properties all over again. Every time we meet a dog, we do not need to learn that it barks, is furry, has four legs, and likes chasing toys. Once we know it is a dog, we know it likely has those traits.

What is interesting about categories, as mentioned in Chapter 2, is that we can apply fuzzy logic to them. We can have creatures that span multiple categories or multiple creatures in one category that don’t seem related (for example, ostrich, penguin, and bluebird are all birds). Categories are formed because they are useful and typically follow biological, physical, or legal laws, but their utility also necessitates keeping them appropriately general to avoid ending up with as many categories as items. The categories we form are not strict criteria or somehow determinative. They are useful, but they have limits. Stereotypes that give rise to racism or sexism are good examples. Many stereotypes are based on statistical trends in differences between groups, but these trends do not mean that individuals should be judged using those statistics or that those statistics give us any idea of the reasons why those differences exist (such as discrimination, biology, traditional cultural roles, or history).

We learn these categories and laws at a young age. Elizabeth Spelke and Renee Baillargeon have shown that even three-month-old infants have expectations based on natural laws of physics. They expect two objects moving together to be connected in some way, and they expect solid objects to remain solid such that other objects can’t move through them. These early indications of our understanding of basic physical laws support the idea that we form categories early based on those observable laws, but infants do not fully understand the laws they are using to reason about the world. Even adults don’t often fully understand physics; instead, we describe what we tend to observe, which sometimes means we are not exact or even mischaracterize what might happen.

As infants, we also appear to understand the difference between animate and inert objects. We treat inert objects differently, and we do not ascribe any innate “essence” to them. If we dress up a lion or even paint it with stripes and shave its mane, small children still call it a lion. Its “lion-ness” is not in how it looks. If we change a coffeepot into a bird feeder, children and adults will say it is now a bird feeder. Its function is its essence, and as its function changes, so does its essence.

As we reason about animate and inert objects, we reason about other people’s minds. We don’t use strict scientific principles or black and white algorithms to determine why people behave a certain way or how they may choose to behave. Instead, we use observations from experience and develop models of likely behaviors and reasons to explain other people’s minds. These explanations are not perfectly accurate, but they are typically correct and help us connect with others. At an early age, we use other people’s gaze direction to help us understand what they are thinking. Infants look at their parents’ eyes when confused, and they look where their parents are looking to figure out what is interesting in the environment. Joint attention (sharing attention on the same object or event) is an ability we develop early and helps us connect with people over shared interests.

People are not typically good at using logic to solve problems unless the problem is a cost-benefit question in which someone who receives the benefit without paying the cost is a “cheater.” Finding cheaters seems to be hardwired into human reasoning, but applying that logic to other problems is not. Mathematics is a good example of a system of logic that humans appear disposed to use in ways related to basic survival, but they do not readily apply them beyond those basic functions without training. Increasing mathematical skills, or any logical skills, involves practice. Like the brain itself, these systems are built from very small pieces (understanding basic numeracy and “smaller” and “greater” than) to larger units (counting to 100 and beyond, adding) to even more complex systems (number sets, algebra, calculus).

When students learning math have to start from the small pieces to solve complex problems, the process is challenging and consumes considerable resources. When they can build the intermediate units and use those automatically, they can start from only one or two levels lower than the problem in front of them. They can reduce the load, but they had to spend time and resources building those units. Without regular practice and a reason to build those units, they will use the small pieces for each problem presented. People are not unintelligent, but we are working with a brain adapted for living a foraging and/or hunting lifestyle. Small, discrete numbers, highly spatial problems, and basic survival questions are ingrained in us, but abstract algebra is not.