Summary
Daniel Kahneman – Thinking, Fast and Slow
Eindhoven University of Technology
0HV60 – Thinking and Deciding
,PART I – TWO SYSTEMS
1 THE CHARACTERS OF THE STORY
The two systems in the mind are:
● System 1 (automatic system), which operates automatically and quickly, with little or no sense
of effort and no sense of voluntary control. The capabilities of this system include innate skills
that we share with other animals, but also learned associations and skills.
● System 2 (effortful system), which allocates attention to the effortful mental activities that
demand it. The operations of this system are often associated with the subjective experience
of agency, choice, and concentration. Operations in this system are disrupted when attention
is drawn away.
System 2 has some ability to change the way System 1 works, by programming the normally
automatic functions of attention and memory. Since our attention has a limited capacity, intense
focusing on a task can make people effectively blind, even to stimuli that normally attract attention.
So, while seeing and allocating are automatic functions of System 1, they depend on the allocation of
some attention to the relevant stimulus.
System 1 constantly generates suggestions for System 2 in the form of impressions, intuitions,
intentions and feelings. Generally, System 2 adopts these suggestions. When System 1 runs into
difficulty (e.g. a question which it cannot answer), System 2 is activated for support. The division of
work between the two systems minimises effort and optimises performance. A limitation of System 1
is that it cannot be turned off. One of the tasks of System 2 is to overcome the impulses of System 1,
System 2 is in charge of self-control.
The different systems become apparent in illusions. While System 1 always reacts to the illusion (e.g.
the Müller-Lyer illusion), System 2 tells us not to believe the intuitive suggestion System 1 provides.
2 ATTENTION AND EFFORT
Eckard Hess found pupils to be sensitive indicators of mental effort, the peak pupil size coinciding
with maximum effort. The pupils offer and index of the current rate at which mental energy is used.
The response to mental overload is selective and precise: System 2 protects the most important
activity so it receives the attention it needs; “spare capacity” is allocated to other tasks. This
sophisticated allocation of attention has been honed by a long evolutionary history; orienting and
responding quickly to the gravest threats or most promising opportunities improved survival chances.
Even now, System 1 takes over in emergencies and assigns total priority to self-protective actions.
A general “law of least effort” applies to both cognitive and physical exertion. This law asserts that if
there are several ways of achieving a goal, people will eventually gravitate towards the least
demanding course of action. Laziness is built deep into our nature.
System 2 is the only system that can follow rules, compare objects on several attributes, and make
deliberate choices between options. System 1 detects simple relations and excels at integrating
information about one thing, but it does not deal with multiple distinct topics at once, nor is it skilled
, at using purely statistical information. A crucial capability of System 2 is the adoption of “task sets”: it
can program memory to obey an instruction that overrides habitual responses. Psychologists speak of
“executive control” to describe the adoption and termination of task sets.
3 THE LAZY CONTROLLER
System 2 has a natural speed, some mental energy is expended in random thoughts and in
monitoring what goes on around you even when your mind does nothing in particular, however, this
causes little strain. It appears to be the case that self-control and deliberate thought draw on the
same limited budget of effort. Also, even in the absence of time pressure, maintaining a coherent train
of thought requires discipline.
Fortunately, not all cognitive work requires much effort. In a state of flow, maintaining focused
attention on an absorbing activity requires no exertion of self-control, thereby freeing resources to be
directed to the task at hand.
It has been found that System 1 had more influence on behaviour when System 2 is busy, meaning
that people are more likely to be tempted when working on a demanding cognitive task. People who
are cognitively busy are also more likely to make selfish choices, use sexist language, and make
superficial judgements in social situations. What can be concluded is that self-control requires
attention and effort. Ego depletion is the phenomenon where, if you have to force yourself to do
something, you are less willing or less able to exert self-control when the next challenge comes
around. Experiments on ego depletion show that all variants of voluntary effort – cognitive, emotional,
or physical – draw at least partly from a shared pool of mental energy. The evidence is persuasive:
activities that impose high demands on System 2 require self-control, and the exertion of self-control
is depleting and unpleasant. The idea of mental energy is not just a metaphor, when one is actively
involved in difficult cognitive reasoning or engaged in a task that requires self-control, their blood
glucose level drops.
One of the main functions of System 2 is to monitor and control thoughts and actions “suggested” by
System 1, allowing some to be expressed directly in behaviour and suppressing or modifying others.
The bat-and ball problem indicates that many people are overconfident, prone to place too much
faith in their intuitions. Failing a minitest like the bat-and-ball problem appears to be, at least to some
extent, a matter of insufficient motivation.
Keith Stanovich draws a sharp distinction between two parts of System 2:
● The algorithmic mind, which deals with slow thinking and demanding computation.
● The rational mind, which provides the ability to resist biases.
In his view, superficial thinking is a flaw in the reflective mind, a failure of rationality.
4 THE ASSOCIATIVE MACHINE
Cognitive scientists have emphasised that cognition is embodied; you think with your body, not only
with your brain. In 1748, the Scottish philosopher David Hume reduced the principles of association to
three: resemblance, contiguity in time and place, and causality. While our concept of association has
radically changed, these three principles still provide a good basis. One way we have advanced
beyond Hume’s ideas is that we no longer think of the mind as going through a sequence of conscious
