Atomic Habits: Tiny Changes, Remarkable Results

The importance of dopamine
: “The importance of dopamine was discovered by accident. In 1954,
James Olds and Peter Milner, two neuroscientists at McGill University, decided to implant an
electrode deep into the center of a rat’s brain. The precise placement of the electrode was
largely happenstance; at the time, the geography of the mind remained a mystery. But Olds
and Milner got lucky. They inserted the needle right next to the nucleus accumbens (NAcc), a
part of the brain that generates pleasurable feelings. Whenever you eat a piece of chocolate
cake, or listen to a favorite pop song, or watch your favorite team win the World Series, it is
your NAcc that helps you feel so happy. But Olds and Milner quickly discovered that too
much pleasure can be fatal. They placed the electrodes in several rodents’ brains and then ran
a small current into each wire, making the NAccs continually excited. The scientists noticed
that the rodents lost interest in everything. They stopped eating and drinking. All courtship
behavior ceased. The rats would just huddle in the corners of their cages, transfixed by their
bliss. Within days, all of the animals had perished. They died of thirst. For more, see Jonah
Lehrer, How We Decide (Boston: Houghton Mifflin Harcourt, 2009).
neurological processes behind craving and desire
: James Olds and Peter Milner, “Positive
Reinforcement Produced by Electrical Stimulation of Septal Area and Other Regions of Rat
Brain,” Journal of Comparative and Physiological Psychology 47, no. 6 (1954),
doi:10.1037/h0058775.
rats lost all will to live
: Qun-Yong Zhou and Richard D. Palmiter, “Dopamine-Deficient Mice Are
Severely Hypoactive, Adipsic, and Aphagic,” Cell 83, no. 7 (1995), doi:10.1016/0092–
8674(95)90145–0.
without desire, action stopped
: Kent C. Berridge, Isabel L. Venier, and Terry E. Robinson, “Taste
Reactivity Analysis of 6-Hydroxydopamine-Induced Aphagia: Implications for Arousal and

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Anhedonia Hypotheses of Dopamine Function,” Behavioral Neuroscience 103, no. 1 (1989),
doi:10.1037//0735–7044.103.1.36.