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Associative learning in plants

Associative learning is the process by which an organism comes to treat one stimulus as a signal for another, so that the first alone elicits the response normally tied to the second.5 Pavlov studied it in dogs, and it was long held to belong to animals with nervous systems.3 A 2016 report of it in pea plants, and a later failed replication, made it a test case for learning without neurons.47

Earliest held
1915, Bayliss, W. M.
Most discussed in
Conditioned Reflexes: An Investigation of the…, 1927
In the library
170 passages in 33 works
Rewritten
2026-10-10
18501875190019251950197520002025Bayliss, W. M., 19151Pavlov, I. P., 19272Fernando CT, Liekens AM, Bingle LE…, 20093Gagliano M, Vyazovskiy VV, Borbély AA…, 20164Markel K, 20205Markel K, 20206Markel K, 20207Gershman SJ, Balbi PE, Gallistel CR…, 20218Levin M, 20259
01

Pavlov's paradigm

Bayliss (1915) described Pavlov's method as resting on two mechanisms, temporary association and the analysers. A stimulus given several times together with an unconditioned stimulus, such as food in the mouth, ends by exciting salivary secretion when presented alone.1 In his 1927 book Pavlov reported dog experiments in which a neutral stimulus applied 10 seconds, 5 seconds or even 1 second after the unconditioned stimulus began gave negative results. He concluded that the first condition for forming a new conditioned reflex is the time relation between the two stimuli.2

02

Claims beyond nervous systems

Fernando and colleagues (2009) noted that associative learning is traditionally thought to be confined to animals with nervous systems.3 They argued that molecular circuits within single cells resemble neural networks, and that chemical kinetics can in principle implement such networks, so nothing confines the mechanisms of associative learning to neural tissue.3 Gagliano and colleagues (2016) went further and claimed that associative learning is an essential component of plant behaviour. They proposed it as a universal adaptive mechanism that arose in plants and animals by convergent evolution.4

03

The pea maze and its replication

Markel (2020) summarised the Gagliano design. Pea plants grew in Y-shaped mazes for three days with fans and lights at the top, and wind consistently preceded light from the same or the opposite arm.6 When growth forced a choice between arms, fans alone were reported to influence direction, while untrained plants were not affected by fans.6 Markel's replication of the protocol used a larger sample and fully blinded analysis. It failed to show the same result. Markel called for further verification before the finding is accepted.7

04

Single cells and networks

Gershman and colleagues (2021) reviewed evidence for Pavlovian conditioning in single cells. They described it as a sophisticated form of learning and left open whether unicellular organisms match that sophistication.8 Levin (2025) reported that simple gene regulatory network models show habituation, sensitization and Pavlovian conditioning. Repeated pairing of an initially neutral node with a stimulus node lets the neutral node trigger the response alone. This is a dynamical state memory that needs no change in network topology or edge strength.9

SourcesEach quotation was checked word for word against the passage it opens.
  1. By the former, a stimulus presented several times in conjunction with an unconditioned stimulus, such as food in the mouth, has ultimately the effect of exciting salivary secretion when presented alone.Bayliss, W. M., 1915 · Principles of General Physiology · open at passage 2192
  2. We thus see that the first set of conditions required for the formation of a new conditioned reflex encompasses the time relation between the presentation of the unconditioned stimulus and the presentation of that agentPavlov, I. P., 1927 · Conditioned Reflexes: An Investigation of the Physiological Activity of the… · open at passage 78
  3. Associative learning is traditionally thought to be confined to animals with nervous systems (Walters et al. 1979; Kandel et al. 2000; Fanselow & Poulos 2004).Fernando CT, Liekens AM, Bingle LE, Beck C, Lenser T…, 2009 · Molecular circuits for associative learning in single-celled organisms · open at passage 2
  4. Our results now show that associative learning is also an essential component of plant behaviour.Gagliano M, Vyazovskiy VV, Borbély AA, Grimonprez M…, 2016 · Learning by Association in Plants · open at passage 16
  5. Learning is demonstrated when presentation of the conditioned stimulus can elicit responses normally associated with the unconditioned stimulus.Markel K, 2020 · Lack of evidence for associative learning in pea plants · open at passage 4
  6. Training consisted of wind consistently preceding light from either the same or the opposite arm of the maze.Markel K, 2020 · Lack of evidence for associative learning in pea plants · open at passage 0
  7. 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.Markel K, 2020 · Lack of evidence for associative learning in pea plants · open at passage 0
  8. It is an open question whether unicellular organisms exhibit a comparable level of sophistication in their learning capabilities.Gershman SJ, Balbi PE, Gallistel CR, Gunawardena J, 2021 · Reconsidering the evidence for learning in single cells · open at passage 4
  9. This is a kind of dynamical state memory that does not require any hardware changes to the topology of the network or the strength of the edges (promoters).Levin M, 2025 · The Multiscale Wisdom of the Body: Collective Intelligence as a Tractable… · open at passage 23
Linked ideas
Conditioned reflexprecursor of / follows
Pavlov's conditioned reflex in dogs supplies the stimulus vocabulary and the paradigm that the plant experiments tried to reproduce.
Basal cognitionrelated to
Claims of learning in plants and single cells belong to the wider argument that cognition does not require a nervous system.
Another non-neural substrate proposed for learning-like memory, here in tissue networks rather than plants.
Network models in which memory and conditioning-like behaviour are sought without neurons.
Early and modern arguments about learning in single cells, the other main non-neural test case.
Disputes over what counts as learning in plants bear on which criteria can be applied outside animals.
Another case in which memory and learning are sought in organisms or cells without conventional neural circuitry.
Lyon calls associative learning in prokaryotes unexplored; plants offer another non-neural case where learning is asked about.
Where it is discussedPassages matching associative learning in pea plants, associative learning, Pavlovian conditioning in plants, neutral stimulus
1927Conditioned Reflexes: An Investigation of the Physiological Activity of the… · Pavlov, I. P.48
2012Evolution of associative learning in chemical networks · McGregor S, Vasas V, Husbands P…17
2009Molecular circuits for associative learning in single-celled organisms · Fernando CT, Liekens AM, Bingle LE…17
2016Learning by Association in Plants · Gagliano M, Vyazovskiy VV, Borbély AA…11
2020Lack of evidence for associative learning in pea plants · Markel K10
2021Behaviorist approaches to investigating memory and learning: A primer for… · Abramson CI, Levin M10
2015The cognitive cell: bacterial behavior reconsidered · Lyon P5
2021Reconsidering the evidence for learning in single cells · Gershman SJ, Balbi PE, Gallistel CR…5
2022Learning in Transcriptional Network Models: Computational Discovery of… · Biswas S, Clawson W, Levin M5
2021Towards the Idea of Molecular Brains · Timsit Y, Grégoire SP4