5 common mental errors that prevent you from good decision making

mental errors

We might like to think of ourselves as the epitome of rationality, executing utmost mental clarity in every of life’s choices. But, that is far from the truth.

If you are human you are irrational and are prone to mental errors.

The key to being rational, therefore, is to eradicate (or at least be aware of) our natural disposition towards mental errors.

To do that, we must know what they are.

So, here is a list of the most common mental errors that cloud your judgement.

1. Survivorship Bias

This is the belief in winners.

For example, “How to have your dream summer body” followed by a picture of an extremely athletic person with a body you really do want this summer. Once we absorb this article we believe that if we too drink celery water three times a day, without making any other lifestyle shifts, we will look just like the person in the picture.

The problem is, there might be 1000 people that tried this diet but didn’t get the same dream body. We just don’t hear of failures. Failure stories don’t make the headlines. Survivorship bias makes us lap up the “winner evidence” but dispel anything that contradicts it (maybe because we can’t find that information).

Survivorship bias isn’t merely saying that a strategy may not work well for you, it’s also saying that we don’t really know if the strategy works well at all. Just because it worked for some people doesn’t mean it will work for you.

2. Loss Aversion

Loss aversion refers to our tendency to strongly prefer avoiding losses over acquiring gains. Research has shown that if someone gives you £10 you will experience a small boost in satisfaction, but if you lose £10 you will experience a significantly higher loss in satisfaction.

The responses are the opposite, but they are not equal in magnitude. 

Our tendency to avoid losses can cause us to make irrational decisions, for example, hoarding our belongings. We are predisposed to feel protective of the things we own and that can lead us to overvalue these items.  For example, keeping all of the clothes we never wear (especially the ones with the labels still on) simply because it causes us too much pain to throw them away. “What a waste!” We would say. You never use them but can’t bear to part with them. That is loss aversion

Similarly, you might feel a small bit of joy when you breeze through green lights on your way to work, but you will get downright angry when the car in front, slowly chugging away at 12 MPH, misses the green light.  Losing out on the chance to make the light is far more painful than the pleasure of hitting it.

3. The Availability Heuristic.

The Availability Heuristic refers to a common mistake that our brains make by assuming that the examples which come to mind first easily are also the most important or even, the most factually correct.

For example, research by Steven Pinker at Harvard University has shown that we are currently living in the least violent time in history. This makes absolute sense if we consider most medieval dinner parties would offer dessert with a slice of serious violence. Quite simply, rates of homicide, rape, and child abuse are all falling. 

Most people are shocked when they hear these statistics. We always hear of violence how can this be true?

Welcome to the availability heuristic.

The answer is that we are not only living in the most peaceful time in history but also the best reported time in history.

We overvalue and overestimate the impact of things that we can remember and we undervalue and underestimate the prevalence of the events we hear nothing about. 

4. Anchoring

This can be seen in the form of advertising, telling you to do one thing but it’s actually sneakily persuading you to do another.

For example, business owners have found that if you say “Limit 12 per customer” then people will buy twice as much product compared to saying, “No limit.”

Perhaps the best example of anchoring can be seen with product pricing. If the price tag on a new watch is £400, you might consider it too expensive. However, if it’s sitting next to a watch for £5,000 than you’ll be convinced that it’s actually quite reasonable. And before you know it you’ve been “anchored”.

5. Confirmation Bias.

Confirmation bias refers to our tendency to search for and favour information that confirms our beliefs while simultaneously disregarding information that contradicts our beliefs. We do this all the time.

The more you believe you know something, the more you filter all information to the contrary.

So, now you know the common mental errors, try to avoid them. It’s a lot easier than it sounds but self-awareness is key!


PCA Law (the Personal Communications Academy For Lawyers) are the legal sector’s specialist providers of conversation-based experiential training products

We are the only Personal Communication Consultancy in the world to work exclusively with lawyers...


We are happy to come in to talk with you at your offices, wherever you’re based, so please contact us at: