Dunbar’s Number

Calling Dunbar’s Numbers
Pádraig MacCarron, Kimmo Kaski, Robin Dunbar
4 Aug 2016

The social brain hypothesis predicts that humans have an average of about 150 relationships at any given time.
Within this 150, there are layers of friends of an ego, where the number of friends in a layer increases as the emotional closeness decreases.

Individuals do not give equal weight to each relationship and evidence from the social brain hypothesis suggests that ego networks are structured into a sequence of layers with the size of each layer increasing as emotional closeness decreases (Dunbar 1998, Hill and Dunbar 2003).
The mean number of friends in each has been found to be around 5, 15, 50 and 150 in the cumulative layers (i.e. on average 10 people in the second layer to make a total of 15) (Zhou et al. 2005, Hamilton et al. 2007).


Raven’s progressive matrices

Raven’s matrices, participants were required to complete the ninth pattern in a 3 × 3 geometric puzzle. They were scored on the number of grids that they answered correctly. Solving the puzzle requires quick and flexible thinking — called fluid intelligence.

see also:

Pearson Education, Inc.


Use of ‘smart drugs’ on the rise (2018)

Use of ‘smart drugs’ on the rise
Nature 05 July 2018

Smart drugs: A dose of intelligence.
Nature. 2016 Mar 3;531(7592):S2-3.
Dance A.

Adderall (amphetamine) and Ritalin (methylphenidate) — treatments for attention-deficit hyperactivity disorder (ADHD)
modafinil, which is a medication for sleep disorders such as narcolepsy.

it is not clear whether the same medications can push a neurologically healthy, well-rested individual onto a higher cognitive plane.

“By far the most commonly used neurocognitive enhancers are nicotine and caffeine,” says Peter Morgan, a psychiatrist at Yale University School of Medicine in New Haven, Connecticut.


many cognitive tests had been designed to assess impairment, not enhancement. For example, people with a brain injury or dementia may struggle with a clock-drawing test, but someone with normal cognition will usually get it right — leaving no room for smart drugs to assist.

regular use of coffee and cigarettes causes consumers’ brains to adapt so that they need the stimulant just to function at their normal cognitive level.


ethical questions. One such concern revolves around social equality. Not everyone has equal access to smart drugs,…

they stick to coffee, tea or energy drinks. Morgan, for his part, suggested that the same cognitive benefits can be achieved by simply taking a refreshing nap.

Can You Make Yourself Smarter?
The RSA, 2014

nicotine patch