The philosophy and bioethics community was rocked and in turmoil Friday when they learned that groundbreaking experimental psychologist Professor Harry Harlow had died over 30 years ago. Harlow’s iconic studies of mother and infant monkeys have endured for decades as the centerpiece of philosophical debate and animal rights campaigns. With news of his death, philosophers worried that they would now need to turn their attention to new questions, learn about current research, and address persistent, urgent needs in public consideration of scientific research and medical progress. Scientists and advocates for a more serious contemporary public dialogue were relieved and immediately offered their assistance to help others get up to speed on current research.

To close the chapter, psychologists at the University of Wisconsin provided the following 40 year retrospective on Harlow’s work and its long-term impact (see below).

Internet reaction to the scientists’ offering was swift, fierce, and predictable.

“We will never allow Harlow to die,” said one leading philosopher, “The fact is that Harlow did studies that are controversial and we intend to continue making that fact known until science grinds to a halt and scientists admit that we should be in charge of all the laboratories and decisions about experiments. It is clear to us that we need far more talk and far less action. Research is complicated and unpredictable–all that messiness just needs to get cleaned up before research should be undertaken.”

Animal rights activists agreed, saying:

“For many decades Harlow and his monkeys have been our go-to graphics for protest signs, internet sites, and articles. It would simply be outrageously expensive and really hard to replace those now. Furthermore, Harlow’s name recognition and iconic monkey pictures are invaluable, irreplaceable, and stand by themselves. It would be a crime to confuse the picture with propaganda and gobbledygook from extremist eggheads who delusionally believe that science and animal research has changed anything.”

Others decried what they viewed as inappropriate humorous responses to the belated shock at Harlow’s passing.

“It is clear to us that scientists are truly diabolical bastards who think torturing animals is funny. Scientists shouldn’t be allowed to joke. What’s next? Telling people who suffer from disease that they should just exercise and quit eating cheeseburgers?” said a representative from a group fighting for legislation to outlaw food choice and ban healthcare for non-vegans and those with genetic predispositions for various diseases.

A journalist reporting on the controversial discovery of Harlow’s death was overheard grumbling, “But what will new generations of reporters write about? Anyway, the new research is pretty much the same as the old research, minus all the complicated biology, chemistry, and genetic stuff, so it may as well be Harlow himself doing it.”

A fringe group of philosophers derisively called the “Ivory Tower Outcasts” for their work aimed at cross-disciplinary partnerships in public engagement with contemporary ethical issues made a terse statement via a pseudonymous social media site.

“We told you so. Harlow is dead. Move on. New facts, problems require thought+action (ps- trolley software needs upgrade, man at switch quit)”

Harlow himself remained silent. For the most part, his papers, groundbreaking discoveries, and long-lasting impact on understanding people and animals remained undisturbed by the new controversy.

Statement from Psychologists:

Harlow’s career spanned 40+ years and produced breakthroughs in understanding learning, memory, cognition and behavior in monkeys1 (see Figure 1). In a time period where other animals were generally thought of as dumb machines, Harlow’s work demonstrated the opposite — that monkeys, like humans, have complex cognitive abilities and emotional attachments. Harlow and his colleagues developed now classic ways to measure cognition2,3. For example, the Wisconsin General Test Apparatus (WGTA; see Figure 1), in which monkeys uncover food beneath different types of colored toys and objects, allowed scientists to understand how monkeys learn new things, remember, and discriminate between different colors, shapes, quantities, and patterns.

The discoveries of Harlow and his colleagues in the 1930s and forward provided the foundation not only for changes in how people view other animals, but also for understanding how the brain works, how it develops, and –ultimately–how to better care for people and other animals.

In the last decade of his long career, Harlow, his wife Margaret– a developmental psychologist, and their colleagues, again rocked the scientific world with a discovery that fundamentally changed our biological understanding.3 Contrary to prevailing views in the 1950s and before, the Harlows’ studies of infant monkeys definitively demonstrated that mother-infant bonds and physical contact—not just provision of food—are fundamentally important to normal behavioral and biological development. Those studies provided an enduring empirical foundation for decades of subsequent work that shed new light on the interplay between childhood experiences, genes, and biology in shaping vulnerability, resilience, and recovery in lifespan health.

For a brief time at the very end of his career, Harlow performed a small number of studies that have served as the touchstone for philosophers, animal rights groups, and others interested in whether and how animal research should be done. The most controversial of the studies are known by their colloquial name “pit of despair” and were aimed at creating an animal model of depression. In this work, fewer than 20 monkeys were placed in extreme isolation for short periods (average of 6 weeks) following initial infant rearing in a nursery.

At the time, the late 1960s, the presence of brain chemicals had recently been identified as potentially critical players in behavior and mental illnesses like depression and schizophrenia. New understanding and treatment of the diseases was desperately needed to address the suffering of millions of people. Available treatments were crude. They included permanent institutionalization– often in abject conditions, lobotomy (removing part of the brain), malaria, insulin, or electric shock therapies. As some scientists worked to uncover the role of brain chemicals in behavior and mood, others worked to produce drugs that could alter those chemical networks to relieve their negative effects. In both cases, animal models based on similar brain chemistry and biology were needed in order to test whether new treatments were safe and effective. It was within this context that Harlow and his colleagues in psychiatry studied, in small numbers, monkeys who exhibited depressive-like behaviors.

By the 1970s and over the next decades, scientists produced medications that effectively treat diseases like schizophrenia and depression for many people. The therapies are not perfect and do not work for everyone, which is why research continues to identify additional and new treatments. Regardless, there is no question that the suffering of millions of people has been reduced, and continues to be alleviated, as a result of new medications and new understanding of the biological basis of disease.

Looking back while moving forward

Nearly 50 years later, it is difficult to imagine the time before MRI and neuroimaging and before the many effective treatments for depression, schizophrenia and other diseases. It is perhaps even more difficult to imagine a time in which people believed that genes and biology were destiny, that other animals were automatons, or that mothers were only important because they provided food to their children. Casting an eye back to the treatment of monkeys, children, and vulnerable human populations in medical and scientific research 50 years ago, or even 30 years ago, is difficult as well. Standards for ethical consideration, protections for human and animal participants in research, and the perspectives of scientists, philosophers, and the public have all continued to change as knowledge grows. Yet, what has not changed is an enduring tension between the public’s desire for progress in understanding the world and in reducing disease and the very fact that the science required to make that progress involves difficult choices.

There are no guarantees that a specific scientific research project will succeed in producing the discoveries it seeks. Nor is there a way to know in advance how far-ranging the effect of those discoveries may be, or how they may serve as the necessary foundation for work far distant. In the case of Harlow’s work, the discoveries cast a bright light on a path that continues to advance new understanding of how the brain, genes, and experiences affect people’s health and well-being.

In the 30 years since Harlow’s death, new technologies and new discoveries—including brain imaging (MRI, PET), knowledge about epigenetics (how genes are turned on and off), and pharmacotherapies—have been made, refined, and put into use in contemporary science. As a result, scientists today can answer questions that Harlow could not. They continue to do so not because the world has remained unchanged, or because they lack ethics and compassion, but because they see the urgent need posed by suffering and the possibility of addressing global health problems via scientific research.

Harlow’s legacy is a complicated one, but one worth considering beyond a simple single image because it is a legacy of knowledge that illustrates exactly how science continues to move forward from understanding built in the past. An accurate view of how science works, what it has achieved, what can and cannot be done, are all at the heart of a serious consideration of the consequences of choices about what scientific research should be done and how. Harlow and his studies may well be a touchstone to start and continue that dialogue. But it should then be one that also includes the full range of the work, its context and complexity, rather than just the easy cartoon evoked to draw the crowd and then loom with no new words.

Allyson J. Bennett, PhD

The author is a faculty member at the University of Wisconsin-Madison. The views and ideas expressed here are her own and do not necessarily represent those of her employer.



1 Suomi SJ & Leroy, HA (1982) In Memoriam: Harry F. Harlow (1905-1982). American Journal of Primatology 2:319-342. (Note: contains a complete bibliography of Harlow’s published work.)

2Harlow HF & Bromer J (1938). A test-apparatus for monkeys. Psychological Record 2:434-436.

3Harlow HF (1949). The formation of learning sets. Psychological Review 56:51-65

4Harlow HF (1958). The nature of love. American Psychologist 13:673-685.