SYSTEM 1, SYSTEM 2, AVAILABILITY HEURISTIC, AVAILABILITY CASCADE, AVAILABILITY ENTREPRENEURS, ILLUSORY TRUTH EFFECT, and MERE EXPOSURE EFFECT
Human beings can arrive at conclusions by two systems. SYSTEM 1 is via certain processes the brain has built over time (mental shortcuts) based on previous experiences and instincts. System 1 is called the heuristic or instinctive system. It is automatic (meaning it kicks in on its own) and therefore easier (it doesn't require any effort). It's also unconscious (the person is not aware) and time-efficient (because it can help you arrive at a decision in seconds). System 1 is common to all animals including humans. SYSTEM 2 on the other hand is based on rules, logic, information gathering, and active thinking. This is the hallmark of intelligence. Because it is recent on the evolutionary scale, it's only the primates, especially, humans that have system 2. Lower animals have only system 1.
System 2 is more time-consuming and it requires effort. Your brain automatically prefers to use less resources; thus it prefers to make decisions using system 1 while it takes a conscious effort to get your system 2 working everytime you need it. While it might be prudent to use system 1 for trivial daily decisions, one needs to try to use system 2 for major and complex life decisions as system 1 may produce serious errors in these situations.
There are many ways heuristics (aka mental shortcuts, system 1) determine people's decisions. One example is the AVAILABILITY HEURISTIC. An idea that is being much talked about publicly ("trending") is said to be "available". The word "available" means it's available in people's memory and people can easily find examples to cite to buttress their opinion even though the opinion may be wrong. In other words, repetitive public discourse of an idea makes it available. Science has confirmed that people unconsciously tend to believe something if it's available. Even if it's a lie, if it is repeated long enough, it becomes available and becomes the truth.
For instance, celebrity divorces are more reported in the media than divorces by regular people. Therefore celebrity divorce is an "available" idea and thus without conducting any research about it, most people will conclude that celebrities do divorce more than regular people. This might not be true but who cares? It's been repeated long enough (that is, repetitively reported and talked about) and thus it has become the truth. Other examples are:
"Nollywood actors and actresses die more than regular people"
"Male doctors are more randy than other males"
"Air crashes are commoner than other accidents"
Etc etc
Rather than thinking statistically (using system 2), for instance, to find out the ratio of nollywood deaths to the rest of the population or how many doctors are indeed randy compared to other people, people use the mental shortcut called the availability heuristic (a system 1 protocol that says an idea is true if it's popularly talked about). Other examples are feminism which is getting more believers because it is trending and terrorism that increased because of media attention. It doesn't have to be all negative though: a whole society can embrace a positive paradigm shift all because of the availability heuristic.
The process by which an idea becomes available (i.e., become a topic of public discussion) is called AVAILABILITY CASCADE. Some people pick up the idea and for various reasons (whether positive or negative) begin to push it into the consciousness of other people. Such people are called AVAILABILITY ENTREPRENEURS.
An example of availability entrepreneurs is the media (so called "media frenzy" or "sensational journalism"). Journalists and publishers want to make money and in the era of the internet, they want clicks. So they push news that they consider "newsworthy". By so doing, they influence public thinking. As I said above, because they report nollywood deaths and celebrity divorces more for instance, they push people into that heuristic. Advertising agencies are another example. Even internet services like Facebook, YouTube, and Google search can influence how you think just by what they push to you everytime you scroll. An example is the allegation that these services influenced how people voted in the 2016 American presidential election.
Politicians and even regular people who are influential in our various social networks can generate availability cascades. I can never forget that clerics, especially the pastorpreneurs, are very good availability entrepreneurs. Getting an idea repetitively talked about is one way to make people believe it. Remember. Repeat something long enough and it becomes the truth.
The ILLUSORY TRUTH EFFECT is another heuristic that makes people believe that something is true because they're used to it. If presented with 2 choices or ideas, the illusory truth effect says people may unknowingly tend to choose the more familiar option.
Someone raised in a Muslim family or society may tend to consider Islam as the only truth partly because he's used to it. The same thing for someone raised in a Christian family or society. They have been repetitively exposed to it since childhood. They are thus familiar with it and will tend to consider it to be the truth. If you pick Femi (a typical Nigerian) and Smith (a typical Norwegian) and ask them if voodoo can stop a bullet from penetrating the skin, Femi will likely say "Yes" while "Smith" will likely say "No". This is the illusory truth effect.
And yet another heuristic is MERE EXPOSURE EFFECT. This says that even though you shouldn't have liked something, you may end up liking it if you're sufficiently exposed to it. This is one way by which trashy songs "grow" on people. Radio stations keep playing the song all the time. DJ's play the same song at every party you attend. You're being repetitively exposed to it. All of a sudden, you find yourself downloading it and loving it. It's the same reason why companies advertise their products repetitively on the TV, radio, and even internet. They know that with repetitive exposure, you might somehow fall in love with it.
You hated someone initially but after seeing him constantly for six months, you begin to like him and are now even thinking of marrying him. It could be that you've genuinely discovered that he's the right person for you or it may be your system 1 (heuristic) that, unknown to you, is playing pranks on you via the illusory truth effect or the mere exposure effect (love becomes blind). Then you rush into the marriage but two years thereafter, some things happen that finally trigger your system 2 and your heuristics (system 1) that pushed you into the marriage clears off your brain.
The mere exposure effect is one reason why doctors marry nurses or fellow doctors. Replace marriage with profession or just about anything and you see the mere exposure effect at work. It's one of the reasons why many children also pick up their parents' professions even though they may regret it later. It also played out in how African slaves adopted Christianity. When they first came across it, they hated it but with constant (forceful and traumatic) exposure to it, it "grew" on them and they loved it. They loved it so much that they even mastered it more than the original owners. Mere exposure effect at work!
Someone screams it on a megaphone early in the morning. The same stuff is in the flyers/handbills folks are sharing on the streets. Signboards and billboards are displaying this same thing. When you switch on your TV, it's the same stuff that's on. All your colleagues are spewing the same stuff. Your Facebook timeline is filled with the same stuff. And every other car sticker screams the same thing. There's a chance that you will consider it the truth (via the illusory truth effect) and then love it (via the mere exposure effect). Then you wake up everyday and mutter it to yourself. And then spend large parts of your day reading books about it or you spend few hours per week listening to someone talk about it, trust me, you're stuck on it already. The stuff can be a political party, an electoral candidate, a faith, or any other idea. Advertisers know this trick, so does whoever wants to manipulate us. It's our duty to be smart.
Don't confuse the three. Availability cascade is based on the idea dominating public discourse (trending idea) while the illusory truth effect is based on people's familiarity with the idea which might not necessarily be related to trends and the mere exposure effect is love that's based on sufficient exposure. For instance, the availability cascade pushed many people to start using the iPhone but as they got familiar with the phone, they began to consider it the best phone and because they have used it for a while (sufficient exposure), they're now in love with it. Here's a hack you can use on yourself. Do you want to love something or someone? Expose yourself to it or them constantly!
As I said earlier, heuristics (availability cascade, illusory truth, and mere exposure effect) may have helped you arrive at a few right conclusions but you were only lucky. Heuristics are lotteries that mostly fail. We need better and surer ways of knowing the truth and we can only do this by activating the system 2 in our brains.