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Conditioning of the sensitive plant, Mimosa pudica
... It is unclear how this might have affected the results, though one might suggest that chemical signaling between subjects might have decreased the effect size. One potential difference that might limit the effects of such cross-signaling is the number of groups and randomized aspects spread across subjects (fan plus light against fan versus light, randomization of side, test against control), which was larger than some of the other studies (e.g., experimental against control in Armus, 1970). These contrary pairs (fan and light, side) might have resulted in simultaneous signal releases with contrary effects on the subjects. ...
... Taken together, the results of the studies are mixed, ranging from negative (Holmes & Gruenberg, 1965;Holmes & Yost, 1966) to positive (Armus, 1970;Gagliano et al., 2016) to unclear and possibly with uncontrolled confounds (Haney, 1969;Levy et al., 1970). The results of Gagliano et al. (2016) are among the clearest, and, it is interesting to note, the only one of the studies not to use M. pudica for subjects. ...
... Aside from potential mathematical issues with group studies such as the necessity of having a sufficiently large sample size, there is the issue of housing and caring for all the subjects. In some experiments the subjects were described as being housed or tested together (Armus, 1970;Gagliano et al., 2016;Haney, 1969;Levy et al., 1970), which, given the limits on space and resources, may be a practical necessity given the number of subjects. Using single-subject designs would allow for meaningful demonstrations of causality using fewer subjects, which would be helpful where space is limited. ...
Despite considerable research on the responses of plants to stimuli and a recent surge of interest in “plant intelligence,” few studies have been conducted on classical or respondent conditioning in plants. Studies of respondent conditioning in plants were reviewed, the majority of which used the sensitive plant (Mimosa pudica) as the subjects with seismonastic responses (leaflet-folding and leaf-drooping) as the unconditioned responses, and all of which used group designs. The reported results are mixed, with no replications of positive results. Issues have been noted with the methodology of these studies, including the lack of within-subject demonstrations, choice of putative conditioned stimuli, and potential unplanned interactions between subjects across experimental groups. Recommendations are made for addressing these issues in future research.
... While the experiment reported some conditioned responses to the CS, the experiment is difficult to interpret because of a lack of control groups (Applewhite, 1975). In further research, Armus (1970) replicated the experiment using a similar design and included a backward conditioning control group. However, attempts by Levy et al. (1970) failed to replicate the results of the original Haney experiments thereby calling into question the replicability of Armus (1970). ...
... In further research, Armus (1970) replicated the experiment using a similar design and included a backward conditioning control group. However, attempts by Levy et al. (1970) failed to replicate the results of the original Haney experiments thereby calling into question the replicability of Armus (1970). ...
This article provides an overview of the early Mimosa pudica literature; much of which is in journals not easily accessible to the reader. In contrast to the contemporary plant learning literature which is conducted primarily by plant biologists, this early literature was conducted by comparative psychologists whose goal was to search for the generality of learning phenomena such as habituation, and classical conditioning using experimental designs based on animal conditioning studies. In addition to reviewing the early literature, we hope to encourage collaborations between plant biologists and comparative psychologists by familiarizing the reader with issues in the study of learning faced by those working with animals. These issues include no consistent definition of learning phenomena and an overreliance on the use of cognition. We suggested that greater collaborative efforts be made between plant biologists and comparative psychologists if the study of plant learning is to be fully intergraded into the mainstream behavior theory.
... The question of plant learning through habituation or associative learning has intrigued researchers since the 19 th century. Studies from the 1960s and 70s report mixed results, with some positive (Armus, 1970), others unclear (Haney, 1969;Levy et al., 1970), and some negative (Holmes & Gruenberg, 1965;Holmes & Yost, 1966). Despite these attemps, plant learning studies lack sufficient rigor, appropriate design, and necessary controls, leading to unverified and inconsistent results (Abramson & Chicas-Mosier, 2016;Adelman, 2018;Loy et al., 2021). ...
To facilitate the study of learning in plants we share our experiences of trying to replicate Gagliano et al. (2016) pea plant experiment. In the course of our efforts, we identified eleven issues that must be addressed when attempting to replicate these experiments. The issues range from germination and transplantation of seedlings to experimental design and apparatus issues. We propose a number of solutions to overcome these hurdles.
... The learning can take the form of modifying existing behaviors, or giving rise to new behaviors; and it is interpretable as reflecting either conscious or unconscious detection of the contingency (Rescorla & Holland, 1982). Several studies have addressed the question of whether plants are capable of associative learning, in particular, through Pavlovian learning (Haney 1969 cited in Applewhite, 1975;Armus, 1970;Holmes & Gruenberg, 1965;Holmes & Yost, 1966;Levy et al. 1970). This form of learning creates a link between an originally neutral conditional stimulus (CS) that anticipates a biologically relevant unconditional stimulus (US), resulting in the learning of a new conditional response (CR) to the CS (Pavlov, 1927). ...
In a thought-provoking target article, Segundo-Ortin & Calvo (S&C) discuss the possibility that plants are sentient, focusing on a series of capacities normally attributed only to human and nonhuman animals. S&C propose learning as a marker for sentience. We review studies reporting associative learning in plants and find that they either lack essential controls or fail to produce replicable results. The capacity to learn has not yet been demonstrated in plants, so it cannot be used to support the hypothesis that plants are sentient. Further studies are needed. But agnosticism about sentience should not deter us from investigating unexpected new capacities in plants.
... Needless to say, the research on plant learning and memory is just flowering, and further independent replications are needed before we can claim confidently that plants are able to learn (Abramson & Chicas-Mosier, 2016). In fact, the literature yields a mixed bag of negative (Holmes & Gruenberg, 1965;Holmes & Yost, 1966), positive (Armus, 1970), and unclear results (Haney, 1969;Levy et al., 1970). Adelman (2018) reviews these results and Gagliano et al., (2016) and Markel (2020aMarkel ( , 2020b) discuss the evidence, or lack thereof, for associative learning in plants. ...
... Regarding Associative Learning, few studies show clear evidence of its occurrence in plants, and they all have several limitations (for a review see Adelman, 2018). For example, in Armus (1970), in which a Pavlovian Conditioning procedure was used with Mimosa pudica, darkness (CS) was paired with a shake (US) and the results showed that darkness elicited the defensive response, which consisted of the leaflet folding and the stem drooping. However, darkness is not a neutral stimulus because it elicits the leaflet folding without being paired with the US. ...
Since the beginning of the 21st century, the Minimal Cognition approach has emerged vigorously, focusing on the study of the adaptive behavior of the simplest organisms, including bacteria, assuming that they are sentient and information-processing entities. Although Minimal Cognition has occasionally used Pavlovian methods to try to demonstrate Associative Learning, neither the Psychology of Learning nor the Comparative Psychology traditions are prominent in the movement. However, the Psychology of Learning approach, with its highly sophisticated experimental designs, has done a great deal of research on Associative Learning in animals and carried out several studies on plants and unicellular organisms. The present work offers a comprehensive review of these experimental results, among invertebrates , plants and unicellular organisms (paramecia and the amoeba Physarum policephalum) showing that, while there are increasing instances of Associative Learning in many invertebrate phyla (and also many phyla with no data) there is no adequate evidence of it in unicellular protists (despite more than a century of experiments with paramecia and amoeba) or in plants (despite recent results that so claim). We then consider the alternative offered by Minimal Cognition and suggest some complementary ideas, from a Comparative Developmental Psychology approach, which we call "Minimal Development." Association between events can be considered a basic way to acquire knowledge (or cognition). Consequently, studying association in invertebrates and other kingdoms (protists, plants) can provide useful information about the origin and evolution of cognition, allowing us to know which organisms have shown evidence of learning by association. This review suggests that there is clear evidence of a wide array of associative phenomena in invertebrates , but this evidence is concentrated in a few species, since there is no conclusive evidence showing simple association in pro-tists and plants. As a conclusion, it is argued that association seems to show some limitations as a basic form of describing any behavioral change due to experience (learning) in simple organisms and that the psychology of learning can improve its scope by looking into the tradition of Comparative Psychology, which offers a framework based on phylogenetic and ontogenetic Developmental Psychology.
... Regarding Associative Learning, few studies show clear evidence of its occurrence in plants, and they all have several limitations (for a review see Adelman, 2018). For example, in Armus (1970), in which a Pavlovian Conditioning procedure was used with Mimosa pudica, darkness (CS) was paired with a shake (US) and the results showed that darkness elicited the defensive response, which consisted of the leaflet folding and the stem drooping. However, darkness is not a neutral stimulus because it elicits the leaflet folding without being paired with the US. ...
Since the beginning of the 21st century, the Minimal Cognition approach has emerged vigorously, focusing on the study of the adaptive behavior of the simplest organisms, including bacteria, assuming that they are sentient and information-processing entities. Although Minimal Cognition has occasionally used Pavlovian methods to try to demonstrate Associative Learning, neither the Psychology of Learning nor the Comparative Psychology traditions are prominent in the movement. However, the Psychology of Learning approach, with its highly sophisticated experimental designs, has done a great deal of research on Associative Learning in animals and carried out several studies on plants and unicellular organisms. The present work offers a comprehensive review of these experimental results, among invertebrates, plants and unicellular organisms (paramecia and the amoeba Physarum policephalum) showing that, while there are increasing instances of Associative Learning in many invertebrate phyla (and also many phyla with no data) there is no adequate evidence of it in unicellular protists (despite more than a century of experiments with paramecia and amoeba) or in plants (despite recent results that so claim). We then consider the alternative offered by Minimal Cognition and suggest some complementary ideas, from a Comparative Developmental Psychology approach, which we call "Minimal Development." (PsycInfo Database Record (c) 2021 APA, all rights reserved).
... Needless to say, the research on plant learning and memory is just flowering, and further independent replications are needed before we can robustly claim that plants are able to learn (Abramson & Chicas-Mosier, 2016). In fact, the literature yields a mixed bag of negative (Holmes & Gruenberg, 1965;Holmes & Yost, 1966), positive (Armus, 1970), and unclear results (Haney, 1969;Levy et al., 1970-see Adelman (2018 for a review, and Gagliano et al., 2016;Markel, 2020aMarkel, , 2020b for the latest exchanges on the evidence, or lack of, for associative learning in plant). In light of the inconsistent results being reported, at the Minimal Intelligence Lab, we currently aim to test independently the capacity for replication of Gagliano et al.'s (2016) results. ...
Unlike animal behavior, behavior in plants is traditionally assumed to be completely determined either genetically or environmentally. Under this assumption, plants are usually considered to be noncognitive organisms. This view nonetheless clashes with a growing body of empirical research that shows that many sophisticated cognitive capabilities traditionally assumed to be exclusive to animals are exhibited by plants too. Yet, if plants can be considered cognitive, even in a minimal sense, can they also be considered conscious? Some authors defend that the quest for plant consciousness is worth pursuing, under the premise that sentience can play a role in facilitating plant's sophisticated behavior. The goal of this article is not to provide a positive argument for plant cognition and consciousness, but to invite a constructive, empirically informed debate about it. After reviewing the empirical literature concerning plant cognition, we introduce the reader to the emerging field of plant neurobiology. Research on plant electrical and chemical signaling can help shed light into the biological bases for plant sentience. To conclude, we shall present a series of approaches to scientifically investigate plant consciousness. In sum, we invite the reader to consider the idea that if consciousness boils down to some form of biological adaptation, we should not exclude a priori the possibility that plants have evolved their own phenomenal experience of the world.
This article is categorized under: Cognitive Biology > Evolutionary Roots of Cognition
Philosophy > Consciousness
Neuroscience > Cognition
... Some of these disputes center around particular terminology and language, but some basic empirical questions remain contentious, including the simple question: can plants learn? A series of experiments on associative conditioning have been carried out in plants since the 1960s, notably the efforts of Holmes and Gruenberg, 1965, Haney, 1969, Levy et al., 1970, and Armus, 1970. These studies generally failed to observe conditioning in plants, and those that concluded in favor of conditioning lacked sufficient controls to rule out other explanations, as reviewed by Adelman, 2018. ...
Gagliano et al. (Learning by association in plants, 2016) reported associative learning in pea plants. Associative learning has long been considered a behavior performed only by animals, making this claim particularly newsworthy and interesting. In the experiment, plants were trained in Y-shaped mazes for 3 days with fans and lights attached at the top of the maze. Training consisted of wind consistently preceding light from either the same or the opposite arm of the maze. When plant growth forced a decision between the two arms of the maze, fans alone were able to influence growth direction, whereas the growth direction of untrained plants was not affected by fans. However, a replication of their protocol failed to demonstrate the same result, calling for further verification and study before mainstream acceptance of this paradigm-shifting phenomenon. This replication attempt used a larger sample size and fully blinded analysis.
... Some of these disputes center around particular terminology and language, but some basic empirical questions remain contentious, including the simple question: can plants learn? A series of experiments on associative conditioning have been carried out in plants since the 1960s, notably the efforts of Holmes and Gruenberg, 1965, Haney, 1969, Levy et al., 1970, and Armus, 1970. These studies generally failed to observe conditioning in plants, and those that concluded in favor of conditioning lacked sufficient controls to rule out other explanations, as reviewed by Adelman, 2018. ...
Gagliano et al. (Learning by association in plants, 2016) reported associative learning in pea plants. Associative learning has long been considered a behavior performed only by animals, making this claim particularly newsworthy and interesting. In the experiment, plants were trained in Y-shaped mazes for 3 days with fans and lights attached at the top of the maze. Training consisted of wind consistently preceding light from either the same or the opposite arm of the maze. When plant growth forced a decision between the two arms of the maze, fans alone were able to influence growth direction, whereas the growth direction of untrained plants was not affected by fans. However, a replication of their protocol failed to demonstrate the same result, calling for further verification and study before mainstream acceptance of this paradigm-shifting phenomenon. This replication attempt used a larger sample size and fully blinded analysis.
... Some of these disputes center around particular terminology and language, but some basic empirical questions remain contentious, including the simple question: can plants learn? A series of experiments on associative conditioning have been carried out in plants since the 1960s, notably the efforts of Holmes and Gruenberg, 1965, Haney, 1969, Levy et al., 1970, and Armus, 1970. These studies generally failed to observe conditioning in plants, and those that concluded in favor of conditioning lacked sufficient controls to rule out other explanations, as reviewed by Adelman, 2018. ...
Gagliano et al. (Learning by association in plants, 2016) reported associative learning in pea plants. Associative learning has long been considered a behavior performed only by animals, making this claim particularly newsworthy and interesting. In the experiment, plants were trained in Y-shaped mazes for 3 days with fans and lights attached at the top of the maze. Training consisted of wind consistently preceding light from either the same or the opposite arm of the maze. When plant growth forced a decision between the two arms of the maze, fans alone were able to influence growth direction, whereas the growth direction of untrained plants was not affected by fans. However, a replication of their protocol failed to demonstrate the same result, calling for further verification and study before mainstream acceptance of this paradigm-shifting phenomenon. This replication attempt used a larger sample size and fully blinded analysis.
... A series of experiments on associative conditioning have been carried out in plants since the 1960s, notably the efforts of Holmes and Gruenberg (Holmes and Gruenberg, 1965) , Haney (Haney, 1969) , Levy et al . (Levy et al. , 1970) , and Armus (Armus, 1970) . These studies generally failed to observe conditioning in plants, and those that concluded in favor of conditioning lacked sufficient controls to rule out other explanations, as reviewed by Adelman (Adelman, 2018) . ...
Gagliano et al. (Learning by association in plants, 2016) reported associative learning in pea plants. Associative learning has long been considered a behavior performed only by animals, making this claim particularly newsworthy and interesting. In the experiment, plants were trained in Y-shaped mazes for three days with fans and lights attached at the top of the maze. Training consisted of wind consistently preceding light from either the same or the opposite arm of the maze. When plant growth forced a decision between the two arms of the maze, fans alone were able to influence growth direction, whereas the growth direction of untrained plants was not affected by fans. Importantly, some plants were trained to grow towards the fan and others to grow away, demonstrating the flexibility of associative learning. However, a replication of their protocol failed to demonstrate the same result, calling for further verification and study before mainstream acceptance of this paradigm-shifting phenomenon. This replication attempt used a larger sample size and fully blinded analysis.
... This form of learning is ubiquitous in the animal kingdom 17,18 , including all major vertebrate taxa and several invertebrate species 19 and can also be implemented in artificial networks and machines 20 . Whilst the possibility that plants also learn by association has been considered by earlier studies 21,22 , our current study provides the first unequivocal evidence. ...
... This form of learning is ubiquitous in the animal kingdom 17,18 , including all major vertebrate taxa and several invertebrate species 19 and can also be implemented in artificial networks and machines 20 . Whilst the possibility that plants also learn by association has been considered by earlier studies 21,22 , our current study provides the first unequivocal evidence. ...
In complex and ever-changing environments, resources such as food are often scarce and unevenly distributed in space and time. Therefore, utilizing external cues to locate and remember high-quality sources allows more efficient foraging, thus increasing chances for survival. Associations between environmental cues and food are readily formed because of the tangible benefits they confer. While examples of the key role they play in shaping foraging behaviours are widespread in the animal world, the possibility that plants are also able to acquire learned associations to guide their foraging behaviour has never been demonstrated. Here we show that this type of learning occurs in the garden pea, Pisum sativum. By using a Y-maze task, we show that the position of a neutral cue, predicting the location of a light source, affected the direction of plant growth. This learned behaviour prevailed over innate phototropism. Notably, learning was successful only when it occurred during the subjective day, suggesting that behavioural performance is regulated by metabolic demands. Our results show that associative learning is an essential component of plant behaviour. We conclude that associative learning represents a universal adaptive mechanism shared by both animals and plants.
A selective review of the rapid movement displayed by the “sensitive” plant, Mimosa pudica is presented. This paper attempts to elucidate the similarities that exist between animal systems and the plant Mimosa. Various fundamental analogies are described as follows: (1) Mimosa, like animals, displays behavioral plasticity or modification in response to specific stimuli; (2) Mimosa contains specialized structures which play roles similar to various structures associated with animals. Specialized phloem cells in Mimosa constitute a conduction pathway not unlike a simple nerve in animals. Mimosa motor organs display properties similar to animal muscles. All specialized structures enable Mimosa to exhibit morphological movements via stimulus induction; (3) The mechanisms involved in the animal and Mimosa response appear to be similar at a physiological and biochemical level. These primarily being (a) transmission and propagation of electrical potential, (b) ionic exchange, (c) membrane permeability modification, (d) cation involvement, (e) use of transmitter-like substances, and (f) energy dependence; (4) Similar effects are induced by various chemical agents in Mimosa and animals. Based on these similarities it is suggested that the plant Mimosa contains a neural capacity which manifests itself through a simple “nervous system.” Theoretical interpretations are presented which attempt to relate current psychobiological research to factors involved in Mimosa pudica. The use of Mimosa as a subject of investigation in the neurosciences at the classroom and laboratory research level is stressed.
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