Information
Many of the most striking discoveries from plant studies in the environmental and behavioral sciences—against the intuitive passivity of their object—rely upon demonstrations of plants’ vital activity when responding to informational cues from their environments. Claims for plant signaling and sensing are often anchored by empirical work in the field of behavioral ecology, demonstrating the myriad ways plants can perceive “light, chemicals, touch and gravity, temperature, sound, and electromagnetic forces [ . . . ] using a variety of receptors and feedback mechanisms [ . . . ] The stimuli that plants sense include both abiotic factors and those caused by other plants, microbes, and animals.”[1] Such findings are, at this point, relatively uncontroversial.
It is typical to link these signaling behaviors and sensory capacities to responses and reactions that together demonstrate plants as exhibiting purposeful behavior within their environments and even possessing “active, intentional, and interactional lives.”[2] Plants in this light are positioned as ideal circuits responding and reacting to stimuli, making them legible to the models of environmental perception inherited from cybernetics and linked cognitive science programs of the twentieth and twenty-first centuries.[3] Often underlying this strategic framing is the implication that if plants can be read through the scientific apparatus developed to address and understand human cognition in terms of information, then they might be granted similar status as intelligent and conscious organisms, along with whatever ethical consequences that recognition would entail.
This trajectory of research on plant behavior and perception understood in informational terms came together most visibly during the past two decades under the research program of “plant neurobiology.” In its opening salvo, it aimed “at understanding how plants perceive their circumstances and respond to environmental input in an integrated fashion” and to “illuminate the structure of the information network that exists within plants.”[4] This seemingly delimited scope might have been passed off without all too much controversy in the broader cognitive and behavioral science research communities. A signaletic account of plant behavior building on quantitative models of information processing could have been expected to appeal to broader efforts looking to elucidate the structure and physical correlates of information networks and communicative activities in other organisms.
In practice, we find this to be far from the case. Rather than producing any reconciliation across these research domains, work under the banner of plant neurobiology—or more loosely, “plant signalling and behavior,” as the primary society for this work has since rechristened itself[5]—has been dogged with controversy in cognitive, neurobiological, and plant sciences. Whether because of or despite their often quite narrow and specific empirical results, researchers affiliated with the plant neurobiology research program have been regularly accused of misleading or exaggerated claims about the implications of those results and of stretching terms such as “intelligence,” “communication,” and “consciousness” beyond commonsense connotations and their typical use within both popular and scientific communities. It is not just common, but typical, for studies from plant intelligence advocates to be met with immediate rebukes on these grounds in the pages of the very same journal issues within which their positive claims are published.
Crucially, these tensions persist despite seemingly significant conceptual concessions on the part of these researchers. Language of information, signals, cues, and sensing abounds in their work; however, certain associated terms—“code,” “sign,” “interpretation”—are conspicuously scant. Since the interlocking discourses of information andcode were central to many of the preceding research programs that set the stage for this kind of cybernetic-biological inquiry,[6] the judicious excision of the latter bundle of terms suggests an intentional omission. Though these terms have no doubt lost some of their luster since the heydays of structuralism and semiotics, they are seemingly avoided as much for the risky connotations that used to be their source of rhetorical power: namely, their association with notions of literacy, systematicity, and meaning more broadly. As even the plant intelligence advocates would appear to have it, they are after a restricted form of (natural) communication without, or prior to, culture.
On the other hand, and in fairness to its critics, work concerning plant signaling and communicative behavior often betrays a more ambitious aim: seeking to identify in plants various anatomical and functional correlates of human and animal cognition, as the initial name of plant neurobiology once suggested. With overtones, or even explicit evocations, of Charles and Francis Darwin’s famous suggestion that root tips may act like the brain of the plant, many researchers associated with plant neurobiology can be rightfully characterized as making use of fairly slippery analogies in their characterizations of plant behaviors as neuron-like or otherwise comparable to specific human and animal neurological functions.
This is especially true in the public arena, where restricted claims about plants as vitally active information processors are often quickly transformed into suggestive and charismatic demonstrations of their intelligence. Public faces of this research, such as Stefano Mancuso and Monica Gagliano, or science writers-cum-spokespeople, like Michael Pollan, often lean into this gray area, not least because of its apparent and appealing ethical implications in an era of rampant anthropogenic environmental destruction. Both sides of the debate tend to see this as a, if not the, primary consequence of their argument, which leads to some degree of handwringing by critics wanting to maintain their environmentalist credentials while still rejecting what they see as misleading or pseudoscientific construals of key terms, concepts, and results.
Without wanting to take a strong stance on one side of the controversy or the other, extrapolating from this instance of scientific boundary policing can be extremely revealing both for what it says about standard conceptualizations of plant behavior and physiology and, more generally, what function information is allowed to serve in contemporary scientific models of communication, cognition, and consciousness. The relevant question here is not what ethically entails us to plants only after we have somehow empirically proven them to possess a greater degree of human-like cognition on the basis of their ability to process information, as both the pro- and anti-plant-intelligence camps are often concerned. It is found instead, as Jeffrey Nealon nicely advocates, in “paying closer attention to the power effects rendered by the myriad practices by which we do in fact differentiate ourselves form other forms of life.”[7] We can ask what it is that we want in wanting plants to (not) be intelligent. The organization of these fields is historically such that while reaction to informational stimuli may be granted to plants as material facts, the corollary forms of intelligence or culture addressed by conventional information and communication theories remain a privileged domain for humans. This line is drawn upstream of experimental results.
A restrictive stance on what physical information processing would empirically prove is resonant with the attempts to debunk specific claims for plant intelligence—for example, that stimulus reaction is not necessarily proof of goal-directed behavior, or that electrical signaling in plants has physiological rather than information-integration functions. However, it is even clearer in the attempts to argue a priori that consciousness is precluded from plants. One trend in this respect has been to appeal to a recent popular hypothesis for the evolution of primary consciousness in animals. Termed “neurobiological naturalism,” this theory identifies a strict set of requirements for the initial evolution of image-based and affective forms of consciousness that are needed by highly mobile organisms to effectively navigate their environments. These requirements are the presence of a multicellular organism with a nervous system, relatively complex brain, and diverse array of senses.[8] This specific neurophysiological structure is identified as the only basis of consciousness worthy of the name, and it limits the candidates to vertebrates, arthropods, and cephalopods, anchoring a cerebrocentric norm and prescriptive model of consciousness clearly recognizable to phenomenal human experience.
Working backwards in this way from a picture of human or animal consciousness towards its strict evolutionary and physiological prerequisites would seem to cut against a common picture of the modern cognitive and behavioral sciences. We often tend to think of these cybernetically inflected subjects as being physically and/or quantitatively reductionist in a fashion that points to antihuman or posthuman models of information and intelligence. We might then expect a desire to widen the range of subjects to be addressed by a materialist account of information processing. Yet the tendency for these derived fields to delimit their scope of inquiry makes more sense when we recall that twentieth-century information and communication theories did not begin from bottom-up mathematical analyses of these concepts as abstract entities. Instead, they were predicated on particular and political uses within the human and social sciences.
This has been well demonstrated in historical studies of these disciplines. Bernard Geoghegan, in his recent account of the early years of cybernetics, emphasizes how its research trajectory was institutionally backed with an eye towards applications in liberal social reform programs during the interwar period, prior to more widely recognized military considerations. The Josiah Macy Jr. Foundation and its officers, with their focus on Progressive Era theories of social hygiene, viewed their storied Macy Conferences “as a forum where the rational tasks of the humanities and social sciences could be developed and gradually extended to the natural sciences.”[9] Geoghegan’s account accentuates the degree to which early “cybernetics was a humanism,” only one that relied on the imprimatur of natural science and engineering to bolster the political authority of its technocratic programs and its theories of culture and society.
With this background in mind, we can recognize consequences for certain contemporary information-theoretical models and discourses of communication or cognition. Namely, that they typically move froma subject recognized in advance as intelligent and towards the physical and/or informational correlates of that quality, but they encounter much greater resistance in the reverse direction. Consciousness or cultural activity are often taken as prerequisites to be explained, not something to be demonstrated via the inductive analysis of phenomena related to the integration and transmission of information.
This is well demonstrated via more recent attempts to justify plant intelligence claims through just such a domain-agnostic model: Integrated Information Theory (IIT), a theory of consciousness that aims to define it in quantitative terms as a measure of information integration within a system.[10] IIT has been enrolled by some in the plant neurobiology camp as a candidate theory for justifying their study of plant intelligence.[11] Unsurprisingly, this has been summarily rejected by those opposed to plant neurobiological work because IIT marks as “conscious” entities that are traditionally designated as “nonconscious,” and thus these terms would lose their understood meanings.[12] A kind of “common sense” razor is imposed to answer the question of what consciousness can or cannot cover, enshrining it as a presumption of our models of information and communication rather than an outcome.[13]
The explanatory power accorded to a mechanistic or signaletic conception of information appears to only hold water when the phenomena it seeks to explain are assumed to be already well defined. The circularity of this move has been observed,[14] and it is not clear that attempting to assert novel treatments of such polyvalent terms as “intelligence” or “consciousness” could bring us closer to an objective consensus of their proper domain of application. This is true even when both sides appear to agree that plants are “less” intelligent and/or conscious than other forms of life, and their schism mostly concerns whether it is a difference in degree or in kind. Whether in attempting to analogize from our human experiences or conversely draw a line in the sand across which such concepts cannot be extended, we remain in a scene within which intelligence is something we know ourselves to have and may at best only contingently and partially grant to other kinds of living beings. If we were to abandon the language that invites these comparisons (e.g., plants as information processors or even quasi-brains) and insist on radically alternative conceptual schema for attempting to describe what it is that plants do, would we stop trying to plot them on this graded continuum of life? History and intuition would suggest the answer to this question is a resolute no, but its consideration might invite a crack into the surety of the foundation from which our existing accounts seem unable to depart.
Notes
[1] Richard Karban, Plant Sensing and Communication (University of Chicago Press, 2015), 9.
[2] Travis Brisini, “Phytomorphizing Performance: Plant Performance in an Expanded Field,” Text and Performance Quarterly 39, no. 1 (2019): 5.
[3] See, e.g., Jean-Pierre Dupuy, On the Origins of Cognitive Science: The Mechanization of the Mind (MIT Press, 2009).
[4] Eric D. Brenner et al., “Plant Neurobiology: An Integrated View of Plant Signalling,” Trends in Plant Science 11, no. 8 (2006): 413.
[5] The Society of Plant Signalling and Behavior, “Our Mission,” available at https://www.plantbehavior.org/about-us.
[6] See e.g., Lily E. Kay, Who Wrote the Book of Life? A History of the Genetic Code (Stanford University Press, 2000).
[7] Jeffrey T. Nealon, Plant Theory: Biopower and Vegetable Life (Stanford University Press, 2016), 13.
[8] Lincoln Taiz et al., “Plants Neither Possess nor Require Consciousness,” Trends in Plant Science 24, no. 8 (2019): 677–87; and Todd E. Feinberg and Jon Mallatt, The Ancient Origins of Consciousness: How the Brain Created Experience (MIT Press, 2016).
[9] Bernard Dionysius Geoghegan, Code: From Information Theory to French Theory (Duke University Press, 2023), 41.
[10] Giulio Tononi, “Consciousness as Integrated Information: A Provisional Manifesto,” The Biological Bulletin 215, no. 3 (2008): 216–42.
[11] Pedro A. M. Mediano, Anthony Trewavas, and Paco Calvo, “Information and Integration in Plants: Towards a Quantitative Search for Plant Sentience,” Journal of Consciousness Studies 28, no. 1–2 (2021): 80–105.
[12] Jon Mallatt et al., “Integrated Information Theory Does Not Make Plant Consciousness More Convincing,” Biochemical and Biophysical Research Communications 564 (2021): 166–69.
[13] See also Scott Aaronson, “Why I Am Not an Integrated Information Theorist,” Shtetl-Optimized (May 2014), available at https://scottaaronson.blog/?p=1799.
[14] Chauncey Maher, “Experiment Rather than Define,” Trends in Plant Science 25, no. 3 (2020): 213–14.