Our brains are pretty impressive. The reason you're reading this article right now, probably in a comfortable location with an abundant supply of food and water and safety from any natural predators is that people have had plenty of good ideas over the course of human history. Without putting too fine a point on it, we've won the evolutionary arms race because of our intelligence. So we tend to feel quite good about our cognitive ability to make sense of the world around us. In reality, our brains mislead and trick us every day, from inherent problems in our thought processes themselves through to sensory illusions and faulty memories. Much of the time, we don't even realise we're being tricked. The first step to producing a more accurate internal “map” of reality is recognising common cognitive illusions and biases, like...
\#1 – You prefer information which conforms to your beliefs
Confirmation bias is widespread, and is undoubtedly responsible for many falsely-held beliefs. The best example is the news websites you read: it's rather likely that they conform to your political ideals. This is because we inherently prefer information that confirms what we already think, and have a tendency to ignore or dismiss anything that contradicts or challenges it. This mental bias can lead to the mistaken idea that most people agree about a particular issue, or even that there is no evidence or reason to think the contrary when in fact there is.
This is known as source amnesia, and is a consequence of how your brain stores information. When you recall something, it is re-processed every time, and when it’s placed into long-term “storage” it’s no longer connected to the context in which you learned it. You might read a headline from a dubious source claiming that something mundane like carrots cause cancer. At first you discount it, but over time – as you forget where you learned it from and the broader context of the information – it gains strength. The false idea is planted in your brain, but over time you forget that it’s probably false and just remember the idea itself.
\#3 – You don’t notice obvious changes that occur right in front of you
Since your eyes process a lot of visual information at any given moment, your brain effectively slacks off when it comes to making sense of it, to the point where most people don’t even notice even the most obvious changes to their visual surroundings. A surprising experiment into the phenomenon of “change blindness” involved students (individually) approaching a desk, where a man gave them a form to sign. After the student handed it back, the man ducked down behind the desk and a different man (wearing a different shirt, with different colour hair and obviously distinct facial features) stood up, giving them further instructions and a sheet of information. Only 25 percent of people realised that it was an entirely different person who stood up, because our brain just tells us he must have always looked like that.
Related: YouTube: Change blindness
\#4 – You think those in your “group” are better than others
We’re a tribal, group-oriented species, and because of this we have an inclination to prefer people in our particular group to “outsiders.” The neurotransmitter oxytocin is thought to be responsible, because along with helping us bond with friends and loved ones, it makes us distrust people who aren’t part of our in-group. This goes even further, and can lead us into thinking that our immediate group is inherently better, more talented or more intelligent than other groups. Racism is an obvious example of this bias, but it comes in everyday guises too – such as thinking the players on a rival football team are talentless hacks but your own are world-class superstars in the making, or that your friends are smart but everyone else is stupid.
\#5 – You convince yourself you make good purchases
Post-purchase rationalisation is the process by which you convince yourself that even when you buy something faulty, useless or overly expensive, it was really a good idea all along. You protect your mental state by subconsciously telling yourself it was worthwhile, avoiding the “cognitive dissonance” with a confirmation-bias-like, one-sided analysis of your actions.
\#6 – You don’t judge probability well
The perfect example of our problems with judging probability – or even paying much attention to it – is the risk of death from methods of travelling. Many people inherently see flying as more dangerous than driving, because flying is so much further from our natural activities – we can move along the ground, but not suspended in mid-air. However, a simple look at the odds of dying in a car accident compared to dying in a plane crash show this to be monumentally incorrect. The problem is that even if we know it, we still have trouble seeing car travel as a bigger risk than air travel, because our brains just aren’t that good about thinking realistically about risk.
\#7 – You’re more likely to notice bad news
It’s a common complaint that things are generally getting worse in the modern world, but this is more of a reflection of how we weigh positivity and negativity in our minds than one of reality. Crime, violence, war and more general injustice are on the decline overall, but we tend to think everything is progressively getting worse. This is because it doesn't benefit us to pay attention to the good news as much as it does the bad news. In evolutionary terms, the early human who remembered that some berries are poisonous and acts accordingly is more likely to survive and reproduce than the one who simply remembers that berries taste good and eats whatever he feels like. We're biased towards negativity.
\#8 – You assume people think the same way as you
The phenomenon of projection bias leads us to assume that people generally think like we do, when of course they often do not. It's why happy people can't understand miserable people and vice-versa, because we can't step out of our own minds and see from others' perspectives as well as we think. This can also lead to a belief in a false consensus, in which we assume broad agreement on an issue where there is no such agreement, because we think we're representative of the general population. Basically, we forget we could just be weird.
\#9 – You think things you pay attention to are more frequent than they are
Again, our brain is lazy when it comes to interpreting the mass of information we receive from our senses. You might have been told by somebody who claims to have psychic abilities that the number 11 will become important to you, for example, and all of a sudden you seem to see the number 11 more frequently in day-to-day life. It isn't that you're really becoming surrounded by the number 11; it's just that you've decided to notice it. Similarly, you might feel like you see a car you're considering buying everywhere you go, or notice a lot of pregnant women when you're considering having a baby. There is no increase in frequency; you're just noticing specific things more than usual.
\#10 – Things seem predictable in hindsight
Hindsight really is 20/20. When you know what happened, it's much easier to spot the relevant clues than when it wasn't obvious which were relevant. The September 11 attacks in New York are a perfect example, since it's reported that intelligence agencies knew of “something big” possibly happening, so it seems like they should have been able to prevent it. The only problem is that at the time there were lots of reports of “something big” possibly happening, and the vast majority didn't go anywhere. We forget that at the time, none seemed more likely than any others, so paying undue attention to one small sign over all others would make no sense. We convince ourselves they should have known because our brains turn complex situations into simpler narratives when we know the outcome, ignoring what makes prediction challenging.
\#11 – You think things won't take you as long as they will
If you have a particular task to complete, the estimate you make of how long it will take you will likely be very optimistic. This only occurs when it's your own task, though, if somebody else is doing it we're likely to overestimate how long it will take them. In effect, we think of how long a task requires from us in idealised terms, even if we have direct experience of the same task taking longer in the past. You're liable to blame the delays on outside influence, and so discount the evidence that's presented and still underestimate how long something will take.
\#12 – Your memory can be confabulated
Many people assume that their memories are accurate, but they can easily be skewed or even just completely false. This can happen in many ways, whether it's remembering things which fit your preconceptions or even adding new things for them to fit better with your ideas or even remembering hallucinations or dreams as if they really occurred. Things can be fully made up too, if encouragement is given, which is why confessions gained under torture aren't considered reliable evidence. Not only will people confess to something they didn't do, they might truly believe they did it.
\#13 – You see patterns or connections where none exist
Another evolutionary advantage for humans is the ability to notice patterns. If you see a combination of shapes in the corner of your eye that could look like a bear, say, the early humans who believed it to be a bear (even if it just turned out to be the trunk of a tree seen from a particular angle or a odd-shaped rock) were much more likely to survive than those who just assumed it was a meaningless pattern. If you don't see a pattern where one exists, you could die, if you see one where one doesn't exist, there is little consequence. People may see shapes (like faces or ghost-like figures) in random patterns or believe that something isn't random because there are clusters, for example, when the same artist comes up three times in a row on your MP3 player when you set your music to play at random. This phenomenon led to Apple, for example, to make their iPod “shuffle” less random to help people think it was actually aleatory.