Learning without Brains: a Review of The Hidden Life of Trees: What They Feel, How They Communicate by Peter Wohleben
It can be argued that the most controversial tenet of B. F. Skinner’s behaviorism is the claim that the brain and its popular, nebulous surrogate, the mind, do not control behavior (O’Donohue & Szymanski, 1996). Instead, according to Skinner (1977), behavior is under the control of contingencies in the natural environment. Such an assertion challenges the very roots of psychology. The term, psychology, itself is derived from a Greek term meaning, “the study of the breath, spirit, soul.” Psyche later came to mean the totality of the human mind—conscious and unconscious. Psychoanalysis goes farther as it attempts to analyze the mind, particularly the hidden mind, and specifically maps out portions of the mind. That the mind is the crux of human behavior is treated axiomatically by fields such as cognitive psychology, psychoanalysis, and most types of psychotherapy. These endeavors do not struggle over the cruciality of the mind but assume its centrality and attempt to understand it so that people will learn better and live more peaceful lives. In popular vernacular, people talk about “making up their minds” and “getting their heads straight” so that they will make appropriate decisions and feel better about themselves.
But what if there is a species that has no brain, yet adapts very well to its existing environment as well as to new environments? What if this species lives at least an order of magnitude longer than the average human being? What if this species can communicate with other members, can defend itself against predators, will attempt to reproduce only when conditions are optimal, and is so socialized that it will help other members in times of need? What if there is evidence that this species can learn, has a “memory,” and that it experiences pain and sadness? What if there is a species that can achieve outcomes that human beings, with their large and complex brains, have difficulty achieving? According to author, Peter Wohleben, who conducted his research in the woodlands of Germany, there is such a species, and it is the tree.
The early part of the book deals with how trees can store information without brains. The author postulates that this is done in the tree’s root system in which there are chemical messages and measurable electrical impulses—the “woodwide” web. He also proposes that there are numerous complex systems in the roots of trees that are comparable to those found in animal species. He sees these processes as neurological in nature, even though they do not achieve the status of brains, much like a neural network (Ninness, Ninness, Rumph, & Lawson, 2017).
A radical behaviorist might wonder why the author needs to find a physiological representation of the sophisticated survival actions of trees. Yet, the thrust of the book is not in conflict with radical behaviorism. Nowhere in the book does the author express or imply the notion that these neurological processes alone have a causal relationship to the actions of trees. Rather, these processes are part of the chain of actions that a tree engages in to survive.
How then, does a radical behaviorist regard what the author refers to as “neurological processes,” and where do they stand in relationship to human behavior? Here is a possibility: neurological processes are a link in the chain of behaviors that comprise a larger action. Each link in the chain reinforces the link that precedes it and serves as a discriminative stimulus or a motivating operation (Cooper, Heron, & Heward, 2007, pp. 261–263) for the link that follows it. The neurological processes are critical to the emission of the larger behavior. But the neurological processes are not the sole cause of the larger behavior. The ultimate cause is found in the contingencies provided by the external environment. Let me use a sports analogy. Michael Jordan had remarkably athletic legs. Yet, no one would claim that his legs alone caused him to be a basketball superstar. Rather, the actions of his legs were part of the chain of behaviors that helped him to score points and allowed his team to win basketball games. It is better to have an advanced brain and athletic legs, but the activities of these organs are participants in their respective processes, not the causes of them. Meanwhile, I see no problem with regarding neurological events as part of a causal chain leading to the ultimate behavior (Dougher, 2013), nor do I have any objection to committing some of our resources to integrating neuroscience with behavior analysis (Silva, Goncalves, & Garcia-Mijares, 2007).
Most of the book deals with the successful evolutionary history of trees. Evolutionary principles are of interest to behaviorists, partly because the principles Skinner (1938) used to explain behavior were almost identical to those Darwin (1859) used to describe the origin and diversity of species (Ghiselin, 2018). The reality that common principles can be applied to such diverse subject matters is a source of external validation for both disciplines. Although many people continue to contest the validity of both sciences, the evidence for both has reached the point that we can speak of the facts of evolutionary and behavioral principles.
The author acknowledges that it is difficult to comprehend the actions of a species that operates at an infinitesimally slower pace than humans and that can outlive humans by centuries. Still, his description of the evolution of trees contains facets that are similar to those of humans. It would be a mistake to dismiss an action exhibited by a plant because it is like one that humans perform. All living beings face similar challenges. Some readers will criticize Wohleben for anthropomorphizing and would prefer that he invoked a selection by consequences explanation (Schneider, 2012), rather than inferring that trees had memories and felt pain and sadness. Yet, humans commonly refer to such mental states when explaining their own, other people’s, and some other animals’ behaviors, and our inability to do otherwise may point to the limitations of the language we use or the concepts we have developed. Also, the problem may be a speciesism that only credits humans with the capacity to engage in complex processes and to achieve advanced outcomes. For the most part, I found the author’s descriptions to be materially based and functional, not creationist. Here are some examples:
Trees in a forest will nurture each other. The author reports instances in which trees will nourish the stump of a felled tree, indefinitely, trying to keep it alive. Is this an act of altruism? It is not; it is an act of self-interest. It is better for trees to have healthy neighbors, in case heavy winds or rains strike. Having close neighbors also helps to prevent root systems from drying out in extreme heat. When trees are taken out of forests and placed in farms, these actions disappear, and the longevity of trees decreases to a figure similar to that of humans.
The reproductive activities of trees have evolved in accordance with the realities of the ecosystem in which they participate. The author points out that boar and deer seek out the nutrient-rich beechnuts of beech trees and the acorns of oak trees. If both species of trees bloomed every year, the boar and deer populations would increase to the point that the forests would be picked clean of the blooms of both trees. But they do not bloom every year. They bloom on the average of once every other year, but never simultaneously (causing Wohleben to conclude that the trees have memories and communicate with each other). The boar and deer populations survive but are kept in check. This outcome is beneficial to both species of trees and, ultimately, to both species of animals.
Trees will also form interdependent relationships with some birds. Wohleben points out that when woodpeckers hack at trees for insects and homes, trees have fewer destructive pests to deal with, and the birds have attained food and shelter. Birds also assist in the dissemination of trees by transporting digested seeds from one area of the forest to another.
Is there a case to be made that all livings beings are the same? Of course not. There are differences in physical structure, genes, and environmental history to name a few. Plants respire; animals breathe; humans will never learn to fly. But should we support a dualism in which one set of principles applies to plants and another to animals? Or a dualism in which one set of principles applies to humans, and another to all other animals? We should not. I am proposing a monism in which the same evolutionary and behavioral principles apply to all living beings.
As one reads the book, it is tempting to become seduced into complacency by the remarkable results of evolutionary processes—stunning flowers, soaring birds, and adorable children. Yet, the challenges of survival are enormous, varied, and unpredictable. Extinction is much more likely than survival (Raup, 1991), and evolution will only occur when there have been modest environmental changes. What we look at daily are the species that have managed to evolve and survive. Evolution does not guarantee the survival of species. To the contrary, species will survive only when they are able to meet the harsh requirements of evolution. What we are not looking at daily is the greater number of species that did not meet the conditions necessary to evolve and survive. Only a few will continue in the competition for nature’s resources, especially when they become more limited. The successes of evolutionary processes are often beautiful, but the failures can be as ugly as starvation and the absence of habitat. Dinosaurs presently occupy museums and have become sources of scientific curiosity and childhood amusement. The responsibility of human beings is to stop creating the environmental conditions that are populating the displays of these museums (Heward & Chance, 2010).
What was Skinner’s position on the relationship between the brain and behavior? The evidence is that Skinner consistently acknowledged that the brain was a factor, but not the only factor required to explain behavior (Richelle, 1993). So why is there a debate, and why do so many people misconstrue Skinner’s position on this issue? I suggest three possibilities. First, some confusion probably exists because people often refer to the abstract mind rather than the physical brain as the causal agent in behavior. The brain can be studied; the mind cannot be (Skinner, 1974, 1977). Second, Skinner was adamant that one cannot claim causality between two events unless a researcher experimentally manipulates an independent variable and demonstrates its effects on a dependent variable (O’Donohue & Szymanski, 1996). Research on stimulating and lesioning specific sites of the brains of rats has existed for more than 50 years and has found major effects on the subjects’ behavior (Teitelbaum & Epstein, 1962). Skinner would likely acknowledge the value of such research as well as current research on human brain stimulation (e.g., Coles, Kozak, & George, 2018). Skinner was not opposed to neuroscience, just the exaggerated claims of its proponents (Zilio, 2016). That leads to the third point. Skinner gave high status to behavior and claimed that it should be studied in its own right, not as a manifestation of mysterious internal processes (Richelle, 1993).
In conclusion, The Hidden Life of Trees is a provocative and well-written book that may be read and enjoyed by behavior scientists and behavior analysts with a general interest in science, or by those who may be motivated to question some of their own assumptions about adaptation, neural networks, and the behavior of nonhuman beings. Readers with a minimal background in neuroscience may find themselves reading certain sections more than once, but ultimately the material is understandable and enlightening. Trees exist on a different time scale than humans or other sentient organisms, but they are no less alive or interesting. Perhaps serious exploration of how trees adapt, learn, and communicate by behavior scientists will yield new theoretical insights, and maybe even novel applications to other species.
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