Mirror, Mirror on the Wall: How Evolution Shaped Self-Control


Every Halloween, my neighbor would put a pot full of candy outside his house with a clear set of instructions to the children.

They are to take only 2 pieces of candy each.

I’ve never asked my neighbor how effective his instructions were. I know I would not follow them if I were a child.

Recently, I came across a study that analyzed a similar premise.  In a comparable situation, researchers found that over 50% of children (children were older than 9 and could read) ignored instructions and took over 2 pieces.

However, then the scientists ran the experiment again, changing only one thing. This small change increased compliance rate 5 times. Less than 10% of children ignored the instructions this time.

What did the scientists change? The pot of candy was placed in front of the mirror, so that children could see themselves.

As psychologists experimented with self-awareness (about 40 years ago) they observed something curious.

People would change their behavior when they were observed/evaluated. Alternatively, they thought that they were observed or evaluated.

People would donate more, recycle more, less likely to steal, and more likely to cooperate. The presence of mirrors, cameras, or even poster with eyes would increase pro-social behavior in subjects.

Why would being observed change people’s behavior? The answer lies in the origins of self-control.

The brain’s braking system

We engage in various types of self-control: motor, emotional, cognitive, etc. Yet, in all types of self-control, one brain area consistently activates whenever we exercise it. The area is the right side ventrolateral prefrontal cortex (rVLPFC).

There are left and right VLFPC areas, and the right part is larger (in adults) than the left. It’s the only brain area with size asymmetry. Both areas start the same size, but in adolescence the right size grows larger as teenagers gain more self-control.

Motor Control

rVLPFC is called the brain’s braking system. It earned the name after go-nogo studies. In the go-nogo type of studies, participants are shown a series of letters. All but one of these letters are a go letters.

Participants must press a button as quickly as possible when a go letter appears. Moreover, the letters usually appear about 80% of the time. However, when a participant gets into the habit of pushing a button, a no-go letter appears. That’s when the subject must resist pressing the button and the rVLPFC lights up.

Cognitive Control

Resisting pushing a button is an example of motor control. However, rVLPFC contributes to the inhibition of motor, cognitive, and emotional responses.

In his book, “Social Why Our Brains are Wired to Connect“, Matthew Lieberman uses the following example to illustrate a situation requiring cognitive control. Evaluate statements 1 and 2 and to see whether 3 follows:

1. No addictive things are inexpensive.
2. Some cigarettes are inexpensive.
3. Therefore, some cigarettes are not addictive.

The 3 follows from 1 and 2. Yet, in studies, fewer than half answered the question correctly. The reason for this is belief bias.

Because we know that 3 if false in real life, even if it follows logically from conditions 1 and 2, we have a hard time acknowledging it. Overriding the belief bias in this case would require cognitive control and we would use rVLPFC.

Emotional Control

Two main strategies deal with emotion control. One is suppression and another one is reappraisal.

We employ suppression when we hide our emotions. For example, we can be nervous in front of the client, yet we don’t show the anxiety or fear by suppressing the facial expressions and body language.

We engage in reappraisal when we re-frame the reality. For example, when we get fired we tell ourselves that we did not really enjoy the job anyway. A lot of great quotes involve reappraisal. Consider this “All great beginnings are concealed as painful endings.”

So suppression makes you look relaxed while reappraisal makes you feel relaxed. While both suppression and reappraisal are drastically different strategies to exercise emotional control, both involve rVLPFC.

Another way rVLPFC is involved in emotional regulation is thru affective labeling. Verbalizing negative emotions seems to reduce the intensity of emotions. Labeling negative emotions activates rVLPFC and reduces activity in amygdala.

Researchers suspect that’s one reason meditation works. Since meditators are taught to observe and note their emotions/feelings as they meditate, they engage in affective labeling over long periods of time.

rVLPFC is the area where self-control originates. There’s an empirical evidence showing that people with strong rVLPFC responses have a stronger self-control.

Because rVLPFC is involved in all types of self-control and willpower is like a muscle, improving self-control in one area should enhance willpower in other areas.

This should explain the existence of “keystone habits” introduced by Charles Duhigg in his book “The Power of Habit: Why We Do What We Do in Life and Business“. That’s why we see people who give up smoking often start exercising and eating healthier.

But what does self-restraint have to do with mirrors?

Self-Control and Compliance with Social Norms

Humans are social animals. We are social because living in large groups was once beneficial for survival.

We developed large brains so we could thrive in large groups. Among primates, the human brain can maintain the largest social network (as measured by Dunbar number).

So as we evolved being social, the ability to coexist became important. And getting along often meant suppressing selfish impulses.

Stealing might be beneficial to one individual, but detrimental to the whole of society. Adultery might be tempting in the short run, but eventually is damaging to the group dynamics.

We have a romanticized view of willpower. Willpower is this awesome personal trait that allows individuals to grow and excel. Yet, the real reason we evolved to have self-control is fairly prosaic.

Our ancestors subdued their impulses to steal or cheat because they had to. Those who did not, get kicked out of the tribe and die.

Willpower is an evolutionary necessity that allows us to suppress individual impulses in favor of group goals. And that adaptation gets activated (thru its neural basis rVLPFC) whenever we are being watched or evaluated, or even imagine that we are.

Also, guess which brain region is most consistently activated when you see a picture of your own face? rVLPFC.

So if you are running on willpower, know that more help is always available and is often a reflection away.

By the way, next Halloween I’m lending my neighbor a mirror.

What are the implications?

The implications for behavior change are straightforward:

1. Problems with overeating? One study showed that people ate less of full-fat cream cheese when they faced a mirror. So hanging/installing mirror in the kitchen might help. To prevent mindless snacking you could even buy this (alas not available on Amazon, I checked):

By making the fridge surface reflective, this manufacturer has tapped into thousands of years of evolution.

2. Want to change other people’s behavior? Hanging poster with eyes reduced bike theft in one study. People are more helpful when they see cameras. Students cheated 10 times less in front of a mirror.

3. Do you want to build a new habit? Making your behavior socially visible and letting a group evaluate your progress could help. Perhaps that’s one reason why Alcoholics Anonymous and Weight Watchers have succeeded.

Also, there is a lot of anecdotal evidence about people turning to religion to change their behavior. And what is the idea behind God/Gods? A powerful, omnipresent being(s) who is(are) watching and evaluating your behavior…


Social: Why Our Brains Are Wired to Connect

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