Smart phones on the savannah

So why is it that we humans can go astray in recognizing that we have meaningful choices in our lives and in our organizations, in developing and executing winning strategies, in making the big decisions well when it really counts?

Let’s consider the idea that as individuals we are maladapted for modern society.  One line of thinking and research proposes that we are optimized for hunting antelope, not for meetings, morning commutes, juggling emails, tweets and posts, and strategy execution.

Whether evolution has shaped our cognitive processes in ways that are maladaptive today is a controversial topic – but certainly worth exploring. Even if our thought processes and our genes continue to evolve, the argument can be made that deep-seated psychological processes, some that may even trace back to the time of humans’ and apes’ common ancestors, continue to drive our decision making.

Photo by Adam Jones Adam63 - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=7301921

Running down the antelope

Here’s a short story that illustrates a specific example of human optimization.

Scott Carrier spent 15 years learning how to run down an antelope using the techniques of ancient hunter-gathers.1  His theory, developed with his evolutionary biologist brother David Carrier, was that humans, bipedal mammals, who run on two feet rather than four and who sweat, unlike any other animal, were optimized for long distance running through millennia of running down animal prey.2 Scott spent a decade and a half learning from native tribes in Mexico and elsewhere about their running-hunting traditions, and at various times observing and chasing antelope.


In 1997, he and his brother and several other recreational runners made a valiant attempt to achieve his dream – in a day-long effort, they chased a herd and tried to run a pronghorn antelope – one of the fastest animals on the planet, second only to the cheetah, capable of sprinting up to 60 miles per hour – to exhaustion. They failed. Scott wrote in Running After Antelope, "They blend and flow and change positions. There are no individuals but this mass that moves across the desert like a pool of mercury on a glass table." The antelope, he explained, "used the terrain to ditch us."

Fourteen years later, Outside magazine reported that a group of nine elite marathon runners essentially achieved the Carriers’ quest – for hours they chased (running a 4:36 minute mile along the way!) and finally tired and cornered a male pronghorn antelope.3 They could have easily killed the exhausted antelope - had they wanted to.

From whence we came

It’s no surprise that we are naturally great at more than running down game. Our heritage shaped us in so many ways.

Humans are hunter-gatherers.  That’s what we have been optimized to do since we emerged from the Great Apes 7 million years ago.  For all but an eye-blink of that period, only the last 12,000 years or so, humans hunted wild animals and gathered wild plants rather than feeding themselves by domesticating and eating livestock and crops as we do today.4,5

So what does it mean for us to be optimized as hunter-gatherers?

Cultural anthropologists, evolutionary biologists, evolutionary psychologists and other scientists have built a picture of mankind in the Paleolithic era.  They have found and studied relics – such as cave paintings, bone implements and fire pits – left behind by ancient hunter-gather bands.  They have observed, lived among and surveyed the few hunter-gather peoples remaining in the 20th and 21st centuries – in Africa, Australia, Indonesia, South America and other places with remote and relatively untouched populations.  The have used the tools of genetics and the theories of psychology, sociology, social psychology and sociobiology to try to peek into hunter-gathers thinking and psyche.

Here’s some of what has been discerned or at least speculated. To be great hunter-gatherers, humans and human society evolved in specific ways. Hunter gatherers:

Came together in small groups based on kinship and band or tribe membership. Hunter-gathers lived in bands of 20-50 adults.6 Population density was low.7

Did not have permanent leaders. Instead, the person taking the initiative at any one time depended on the task being performed. They did not have political leaders.8

Lived in an “immediate return economy.” Food was secured day to day rather than amassed and stored as in today’s “delayed return economy.”9

Displayed the social norm of “demand sharing.” Food brought to camp by hunters (typically males) and gatherers (typically females) was claimed and shared by all group members, whether or not they contributed to getting or preparing the it.  This “hyper cooperation” is thought to have contributed to group survival and the avoidance of warfare.10

Had an egalitarian social ethos. Peter Gray, Ph.D., research professor at Boston College, writes that 20th century studies of surviving hunter-gather societies showed that “the dominant cultural ethos was one that emphasized individual autonomy, non-directive childrearing methods, nonviolence, sharing, cooperation, and consensual decision-making. Their core value, which underlay all of the rest, was that of the equality of individuals.”11 Researcher Richard Lee called hunter gathers “fiercely egalitarian.”12 Gray explains, “They would not tolerate anyone's boasting, or putting on airs, or trying to lord it over others. Their first line of defense was ridicule. If anyone--especially if some young man--attempted to act better than others or failed to show proper humility in daily life, the rest of the group, especially the elders, would make fun of that person until proper humility was shown.”10 Thus, hunter-gatherers practiced “reverse dominance” or “counter dominance,” where the many act to deflate the ego of anyone who tries to dominate them, as opposed to a standard dominance hierarchy exhibited by our ape relatives, where a few individuals dominate the many. 13, 14, 15

Led a companionship lifestyle and were a mobile, nomadic group. Hunter-gatherers lived without boundaries. Intimacy was non-exclusive. Connections were voluntary and involved sharing of food, movement, residence, company and memory. Individuals had high autonomy. Hunter-gathers were thus deeply individualistic and yet cooperative. 5, 16, 17

Dealt with a common set of problems, including “giving birth, winning social support from band members, remembering the locations of edible plants, hitting game animals with projectiles, recognizing emotional expressions, protecting family members, maintaining mating relationships, assessing the character of self and others, causing impregnation, acquiring language, maintaining friendships, thwarting antagonists” and more.18

Modern life differs

Lest we think that we exist in settings similar to our ancient ancestors, let’s note some key differences.

Hunter-gathers worked less than we do today. It is thought that they worked, on average, about 6.5 hours a day, whereas people in agricultural and industrial societies work on average 8.8 hours a day.19

With a less complex society, hunter-gathers were subject to less stress than modern humans. “Modern times are not like the times in which our ancestors evolved.” The “mismatch” between now and the past “environment of evolutionary adaptation” (EEA) is thought to be one cause of psychopathology (which, according to Merriam-Webster, is “the psychological and behavioral dysfunction occurring in mental disorder or in social disorganization”). “’Bad news’ is a source of anxiety. We now have daily, or even hourly, access to the bad news of six billion people, more than could be generated by a hunter-gatherer band. Moreover, in the EEA, bad news was probably discussed and so shared with other group members, whereas modern man tends to watch it, or listen to it on his own.”20

Hunter-gathers were not subject to leaders who told them what to do. We modern humans are organized in hierarchical groups, typically acting under the direction of leaders.11

Hunter-gatherers were generally peaceable and cooperative, more so than modern humans. They made decisions by consensus, mostly treated one another kindly, trusted one another, avoided aggression, and felt little need to dominate others in order to get their needs met.8, 21

Our hunter-gatherer ancestors were less likely than we are to stress obedience and responsibility in child training. And they are thought to have generally showed more warmth and affection toward their children.8, 22

Are our traits our problem?

It’s a good guess is that you did not run down an antelope this morning or forage in the forest for food, much less share your bounty with your band, no questions asked. Indeed, the traits that flow from our hunter-gatherer roots may not give us what we need to thrive in modern times: They may get in the way of success in our very different age.

Take our hunter-gatherer instilled instincts for sharing and equal distribution of resources, which evolutionary psychologist Bruce Charlton believes, “remain operative since human nature has not had sufficient time to evolve new adaptations over the past twelve thousand or so years.”23 Yet our society is built on social and business hierarchies and an economic system that produces “haves” and “have nots.” For Charlton, it’s no surprise that many people chafe at and see injustice in these dominance hierarchies and seek a “fairer” distribution of resources.23

Fast food and our "stone age mind"

To make what may be the problem obvious, evolutionary psychologists Leda Cosmides and John Tooby offer the colorful statement (attributed to William Allman): "Our modern skulls house a Stone Age mind."24

Evolutionary psychologists including Sven Walter believe we are adapted for yesterday, not today or tomorrow.  “The human mind, like any other complex feature, was shaped by a process of evolution through natural selection. Its subsystems, the modules, are adaptations for solving recurrent information processing problems that arose in our ancestors' evolutionary environment,” not for “playing chess, passing logic exams, navigating through lower Manhattan, or keeping ideal weight in an environment full of fast food restaurants.” 25

One example of a possible maladaptation from hunter-gatherer times is attention deficit hyperactivity disorder (ADHD).  In a study of two tribal groups in Kenya, one still nomadic, the other settled into villages, researchers identified members of both tribes who displayed ADHA traits and had a gene variant linked to ADHD symptoms. Members of the nomadic tribe with ADHD—the hunters—were better nourished than hunter tribe members without ADHD. Those with the ADHD genetic variant in the settled village had more difficultly in the classroom, a major indicator of ADHD in civilized society. The study concluded that the traits associated with ADHD make for better hunters-gatherers and worse settlers.26, 27

Consider mobile phones

New research conducted by British psychologists shows that young adults use their smartphones roughly twice as much as they estimate that they do. In fact, their study found that these young adults used their phones an average of five hours a day — that’s roughly one-third of their total waking hours.28

On any given day, teens in the United States spend about nine hours using media for their enjoyment, according to the report by Common Sense Media, a nonprofit focused on helping children, parents and educators navigate the world of media and technology.29

Let's just put nine hours in context for a second. That's more time than teens typically spend sleeping, and more time than they spend with their parents and teachers. And the nine hours does not include time spent using media at school or for their homework.

However, cell phone usage, while a dramatic example of difference from times not so long ago, is but a minor difference between how we live and how our hunter-gatherer ancestors lived.  Here’s a table compiled by University of Notre Dame researcher Darcia Narvaez that illustrates big differences.30

Old v new living smart phones on the savannah.PNG



But what if the evolutionary psychologists have it wrong?

Some researchers dispute the ideas that we can understand the mind of the hunter-gatherer and even that we are ill-equipped in significant ways for modern life and decision-making because how we think evolved in a time dissimilar to today.

Scientist David Buller wrote in Scientific American, “The idea that we are stuck with a Pleistocene-adapted psychology greatly underestimates the rate at which natural and sexual selection can drive evolutionary change. Recent studies have demonstrated that selection can radically alter the life-history traits of a population in as few as 18 generations (for humans, roughly 450 years).”  He continued, “Moreover, human psychological characteristics are the product of a developmental process involving interaction between genes and the environment. Even if little genetic evolution has taken place since the Pleistocene, which is doubtful, human environments have changed in profound ways… Any Pleistocene-selected genes we possess will interact with these new environments to produce psychological traits that may differ in important ways from those of our Pleistocene ancestors.”27

We can’t say if this counter to the evolutionary psychologists’ view is definitive, and the extent to which it pulls the rug out from under the “we are maladapted for modern life because of our Paleolithic brain” argument.

But for the purposes of understanding how our brains can lead us astray in making important decisions, which viewpoint is correct may not be relevant.  That’s because even without being able to peer into the thinking of hunter-gathers and without having insight about how our situation differs from that faced by hunter-gatherers, we know that humans have primitive drives that, at times, don’t serve us well.

In basic emotions, we are not so different

Brain research suggests that we and other mammals share primitive emotional responses that direct our thinking and behavior in very basic ways.

Neuroscientist Jaak Panksepp cites evidence that, “primary-process emotional affects” -  feelings - “are mammalian/human birthrights that arise directly from genetically encoded emotional action circuits that anticipate key survival needs.”  He cites “seven primary-process (basic) emotional systems - SEEKING, RAGE, FEAR, LUST, CARE, GRIEF (formerly PANIC), and PLAY - concentrated in ancient subcortical regions of all mammalian brains.” These primordial feelings “inform animals how they are faring in the quest to survive.” The positive emotions return animals “to ‘comfort zones’ that support survival,” and the negative emotions produce “‘discomfort zones’ that indicate that animals are in situations that may impair survival.”33

Panksepp observes, “Our modern evolved forebrain can regulate these emotional arousals.” But that regulation is clearly varied and imperfect: We can be led by our primitive emotions to flawed decisions and actions.33

That we come wired with biases and to take mental short cuts that sometimes ill serve us, that “human decisions tend to systematically deviate from what rational choice models would predict,” is evidenced by research on other primates cited by Yale University psychologists Laurie R. Santos and Alexandra G. Rosati.34

Our biases are shared with our encestors

This research finds that “biases ranging from framing, choice-induced preference changes, peak-end heuristics, the endowment effect, and ambiguity aversion all seem to affect the choices of our primate relatives in much the same way that they affect human choices. That is, many of the classic biases that fill textbooks are not solely the hallmark of human decisions but rather are widely shared with other primate species.” 34

For example,

  • Capuchin monkeys were given tokens to trade for apple pieces. They could choose to trade with two different human experimenters. Over time, they would get the same number of apple pieces, on average, from each experimenter. When they chose the first experimenter, they would be shown one apple piece and then sometimes a second apple piece would be added. When they chose the second experimenter, they would be shown two apple pieces and then sometimes one of the apple pieces would be removed. Over time, the monkeys showed an overwhelming preference for the experimenter who added a piece – choosing the “gains” option – rather than the experimenter who subtracted a piece – the “losses” option.  This mirrors humans’ tendency to avoid options that are framed as a loss.36

  • In a number of experiments, five nonhuman primate species were given food or other items and then asked to trade what they were given for more preferable food or other items of greater value. Across the various species, even the less social orangutans, the primates frequently chose to hold on to less-preferred food or other items rather than to exchange them for more-preferred food or items. This is the same “endowment effect” that humans demonstrate, in which people overvalue something they possess compared to something they do not possess.37

  • Both preschool children and capuchin monkeys were given choices between different colored M&Ms as well as different colored stickers. They were less likely to choose an option they had previously rejected when presented with an equally preferred alternative. Both the children and the monkeys seemed to devalue options not previously selected, “changing their current attitudes and preferences to more closely match the choices they made in previous decisions.” This was evidence of the same “decision rationalization” that adult humans demonstrate to avoid cognitive dissonance.38

  • Squirrel monkeys were presented with two amounts of food, small and large, and learned that whichever pile of food they pointed to they would get the other pile as a reward. In this so-called “reverse contingency task,” the monkeys, without extensive training, could not overcome their bias to reach for the best of possible rewards and thus inevitably wind up with the lesser reward. Humans also have difficulty overcoming their biases in “reverse contingency tasks.”39

Whether we humans are led to bad decision making by traits evolved in our hunter-gather days or by our even more primitive drives is not really the point. What’s most important is that even in this most modern of times we cannot escape the truth that we are wired in ways that produce mental biases and preferences and shortcuts that can lead us astray. Accepting that we are not perfectly logical beings is a first step in understanding why and how we make bad decisions and what we can do to make much better ones.

______________________________

This article is based on my exploration of research that reveals the origins of the mental errors and shortcuts that can lead us to making bad decisions,. This exploration will be the subject of the first chapter of my next book, tentatively titled Big Decisions: Why we make them poorly, how we can make them better.

______________________________

  1. Running After Antelope, Scott Carrier, Counterpoint, 2001
    https://www.amazon.com/Running-After-Antelope-Scott-Carrier/dp/1582431795

  2. “The Energetic Paradox of Human Running and Hominid Evolution,” David R. Carrier, Current Anthropology, August-October 1984 http://biologylabs.utah.edu/carrier/Dave's%20PDF/energetic%20paradox.pdf

  3. “Fair Chase,” Outside Magazine, Charles Bethea, Apr 19, 2011 http://www.outsideonline.com/1915656/fair-chase

  4. Guns, Germs, and Steel: The Fates of Human Societies, Jared Diamond, W.W. Norton & Company, Inc., 1997 https://www.amazon.com/Guns-Germs-Steel-Fates-Societies/dp/0393317552

  5. “Foragers and Others,” The Cambridge Encyclopedia of Hunters and Gathers, Richard B. Lee and Richard Daly, University Press, Cambridge, 1999 http://catdir.loc.gov/catdir/samples/cam034/98038671.pdf

  6. “The Human Nature of Teaching II: What Can We Learn from Hunter-Gatherers?” Peter Gray, Psychology Today Blog, May 2, 2011 https://www.psychologytoday.com/blog/freedom-learn/201105/the-human-nature-teaching-ii-what-can-we-learn-hunter-gatherers

  7. New World Encyclopedia contributors, "Hunter-gatherer," New World Encyclopedia, http://www.newworldencyclopedia.org/p/index.php?title=Hunter-gatherer&oldid=979588 (accessed July 22, 2016)

  8. “Hunter-Gatherers (Foragers),” Carol R. Ember, Explaining Human Culture, July 23, 2014 http://hraf.yale.edu/ehc/summaries/hunter-gatherers

  9. “Immediate-Return Societies: What Can They Tell Us About the Self and Social Relationships in Our Society?” Leonard L. Martin and Steven Shirk, The Self and Social Relationships, edited by Joanne V. Wood, Abraham Tesser and John G. Holmes, Taylor & Francis eBooks, May 2013 https://psyc.franklin.uga.edu/sites/default/files/CVs/Hunters%20and%20gatherers_0.pdf

  10. “High mobility explains demand sharing and enforced cooperation in egalitarian hunter-gatherers,” Hannah M. Lewis, Lucio Vinicius, Janis Strods, Ruth Mace and Andrea Bamberg Migliano, Nature Communications, December 16, 2014 http://www.nature.com/ncomms/2014/141216/ncomms6789/abs/ncomms6789.html

  11. “How Hunter-Gatherers Maintained Their Egalitarian Ways,” Peter Gray, Psychology Today Blog, May 16, 2011 https://www.psychologytoday.com/blog/freedom-learn/201105/how-hunter-gatherers-maintained-their-egalitarian-ways

  12. “Commonalities and Diversities in Contemporary Hunter-Gatherers: From Settlement Archaeology to Development Ethnography,” Richard Borshay Lee, Archeological Papers of the American Anthropological Association, January 2006 http://onlinelibrary.wiley.com/doi/10.1525/ap3a.2006.16.1.157/abstract

  13. Hierarchy in the Forest: The Evolution of Egalitarian Behavior, Christopher Boehm, Harvard University Press, 2001 https://www.amazon.com/Hierarchy-Forest-Evolution-Egalitarian-Behavior/dp/0674006917

  14. “The human socio-cognitive niche and its evolutionary origins,” Andrew Whiten and David Erdal, Philosophical Transactions of the Royal Society B, The Royal Society Publishing, 2012 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3385679/

  15. “On Human Egalitarianism: An Evolutionary Product of Machiavellian Status Escalation?” David Erdal, Andrew Whiten, Christopher Boehm and Bruce Knauft, Current Anthropology, Vol. 35, No.2, April 1994 http://www.unl.edu/rhames/courses/current/readings/erdal.pdf

  16. “Can Hunter-Gatherer Societies Teach Us About Cooperation?” Krystal D'Costa, Anthropology in Practice, Scientific American, April 30, 2015 http://blogs.scientificamerican.com/anthropology-in-practice/can-hunter-gatherer-societies-teach-us-about-cooperation/

  17. “The 99 percent: Development and Socialization Within an Evolutionary Context: Growing Up to Become ‘A Good and Useful Human Being,’” Darcia Narvaez, War, Peace, and Human Nature: The Convergence of Evolutionary and Cultural Views, edited by Douglas P. Fry, Oxford University Press, 2013 https://www3.nd.edu/~dnarvaez/documents/17_Fry_Ch17dpf-edited.pdf

  18. “Evolutionary Psychology: Theoretical Foundations,” Leda Cosmides and John Tooby, Encyclopedia of Cognitive Science, edited by L. Nadel, Nature Publishing Group, 2003 http://www.cep.ucsb.edu/papers/A0529.pdf

  19. “Time, Energy, and the Indolent Savage. A Quantitative Cross-Cultural Test of the Primitive Affluence Hypothesis,” Ross De Forest Sackett, PhD Dissertation, University of California, Los Angeles, 1996

  20. “Evolutionary aspects of anxiety disorders,” John S. Price, Dialogues in Clinical Neuroscience, September 2003 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3181631/

  21. The Foundations of Morality, Henry Hazlitt, Foundation for Economic Education, 1998 https://www.amazon.com/Foundations-Morality-Henry-Hazlitt/dp/1452858152

  22. “Hunter-Gatherer Infancy and Childhood: The !Kung and Others,” Melvin Konner, Hunter-gatherer Childhoods: Evolutionary, Developmental & Cultural Perspectives, Edited by Barry S. Hewlett and Michael E. Lamb, Transaction Publishers, 2005 http://anthro.vancouver.wsu.edu/media/Course_files/anth-302-barry-hewlett/melkonner.pdf

  23. “The inequity of inequality: egalitarian instincts and evolutionary psychology,” Bruce G. Charlton, Journal of Health Psychology, 1997 http://www.hedweb.com/bgcharlton/evolpsych.html

  24. “Evolutionary Psychology: A Primer,” John Tooby and Leda Cosmides, Center for Evolutionary Psychology, University of California Santa Barbara, 1997 http://www.cep.ucsb.edu/primer.html

  25. “Evolutionary Psychology,” Sven Walter, The Internet Encyclopedia of Philosophy http://www.iep.utm.edu/evol-psy/

  26. “Were Hyperactive Hunter-Gatherers Better Adapted Than Their Peers? ADHD and Evolution,” Brian Krans, Healthline, November 25, 2012 http://www.healthline.com/health/adhd/evolution

  27. “The Evolution of ADHD: Social Context Matters,” Dan Eisenberg and Benjamin Campbell, San Francisco Medicine, October 2011 http://evolution.binghamton.edu/evos/wp-content/uploads/2012/02/eisenberg-and-campbell-2011-the-evolution-of-ADHD-artice-in-SF-Medicine.pdf

  28. “You Probably Use Your Smartphone Way More Than You Think,” Carolyn Gregoire, The Huffington Post, November 2, 2015 http://www.huffingtonpost.com/entry/smartphone-usage-estimates_us_5637687de4b063179912dc96

  29. “The Common Sense Census: Media Use by Tweens and Teens,” Common Sense Media Inc., 2015 https://www.commonsensemedia.org/research/the-common-sense-census-media-use-by-tweens-and-teens

  30. “The 99%: Development and Socialization within an Evolutionary Context: Growing Up to Become ‘A Good and Useful Human Being,’” Darcia Narvaez, In D. Fry (Ed.), War, Peace and Human Nature: The convergence of Evolutionary and Cultural Views, Oxford University Press, 2013 http://www3.nd.edu/~dnarvaez/documents/Narvaez99percent2012FINAL.pdf

  31. “Four Fallacies of Pop Evolutionary Psychology,” David Buller, The Sciences, Scientific American, November 1, 2012 http://www.scientificamerican.com/article/four-fallacies-of-pop-evolutionary-2012-12-07/

  32. “Evolutionary Cognitive Psychology,” Peter M. Todd, Ralph Hertwig and Ulrich Hoffrage, The Handbook of Evolutionary Psychology, Volume 2: Integrations, edited by David M. Buss, John Wiley & Sons, Inc. 2005 http://emilkirkegaard.dk/en/wp-content/uploads/David-M.-Buss-Handbook-of-Evolutionary-Psychology.pdf

  33. “Affective neuroscience of the emotional BrainMind: evolutionary perspectives and implications for understanding depression,” Dialogues in Clinical Neuroscience, Jaak Panksepp, December 2010 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3181986/

  34. “The Evolutionary Roots of Human Decision Making,” Laurie R. Santos and Alexandra G. Rosati, Annual Review of Psychology, January 3, 2015 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4451179/

  35. “Emotions and cost/benefit assessment: The role of shame and self-esteem in risk taking,” Daniel M.T. Fessler, Published as a chapter in Bounded Rationality: The Adaptive Toolbox, R. Selten & G. Gigerenzer, eds., 2001 https://www.academia.edu/15177069/Emotions_and_cost-benefit_assessment

  36. “The evolution of decision-making under risk: Framing effects in monkey risk preferences,” Venkat R. Lakshminarayanan, M. Keith Chen and Laurie R. Santos, Journal of Experimental Social Psychology, May 2011 http://www.anderson.ucla.edu/faculty/keith.chen/papers/Final_JESP11.pdf

  37. “The endowment effect in orangutans,” Timothy M. Flemming, Owen D. Jones, Laura Mayo, Tara Stoinski and Sarah F. Brosnan, International Journal of Comparative Psychology, 2012. http://scholarworks.gsu.edu/cgi/viewcontent.cgi?article=1029&context=psych_facpub

  38. “The origins of cognitive dissonance. Evidence from children and monkeys,” Louisa C. Egan, Laurie R. Santos and Paul Bloom, Psychological Science, 2007 http://www.communicationcache.com/uploads/1/0/8/8/10887248/the_origins_of_cognitive_dissonance_-_evidence_from_children_and_monkeys.pdf

  39. “Can squirrel monkeys (Saimiri sciureus) learn self-control? A study using food array selection tests and reverse-reward contingency,” By James R. Anderson, Shunji Awazu and Kazuo Fujita, Journal of Experimental Psychology: Animal Behavior Processes, January 2000 http://psycnet.apa.org/index.cfm?fa=buy.optionToBuy&id=1999-15530-007

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