Definition:

1. Humans have a cognitive limit of approximately 150 people with which they can maintain personal relationships.

Insights:

1. The number (150) has remained relatively constant throughout history, geography, or activity.
2. Dunbar argues that this is directly related the the physical size of the neocortex, the part of the human brain responsible for conscious thought, logic, and language.
3. Organisations should not consist of groups of people in the smallest networks of more than 150 - many organisations use this number as the guide to the maximum number for the efficiency of teams, groups, and departments.

References:

1. Origin: The work of evolutionary biologist Robin Dunbar on the human brain and social groups.

Examples:

1. The size and configuration of armies across the world and throughout history: consist largely of platoons (10-15 soldiers), companies (3-4 platoons), battalions (3-4 companies).

References:

1. Garrett Hardin - described what happens on common land - example of sheep grazing causing a destruction of the land by overuse.
2. John Sulston in a report argues humanity to think beyond competition: '"So long as an excess of competition between nations continues," the report concludes, "the future of humanity is in doubt."'

Insights:

1. Hardin's 1968 paper was controversial as it had no technical solution to the problem of resource allocation, only a "fundamental extension of morality".
2. Taken together, game theory and The Tragedy of the Commons illustrates the destructiveness of competitive self interest.

Definition:

1. Stress can enhance learning on easy tasks, but will impair learning on more difficult tasks.

Insights:

1. Complex tasks require a lot of energy from the brain including working memory, executive processing, decision-making, and attention. Stress impairs the functioning of the prefrontal cortex - where we do our thinking - and the hippocampus - responsible for complex problem solving.
2. We might have the mental capacity but stress can make it challenging to put everything together.

References:

1. In 1905 Robert Yerkes and John Dodson studied stress in mice. The put mice into a box wired with electricity. They found that learning in mice increased with the intensity of electric shocks on simple tasks, but declined with intense shocks on more difficult tasks.