BioelectricaAlterspan Labs
Minds of small things  ·  Article

Behaviour of single cells

Single cells such as Amoeba, Paramecium and Stentor move, feed, regenerate and respond to stimuli without a nervous system. Observers from the 1880s onward described these acts and asked what they show. Binet explained the amoeba's pseudopod by the mechanics of its surface layer.1 Recent authors read single-cell behaviour as evidence of learning without neurons, which makes it central to debates on cognition.9

Earliest held
1888, Binet, A.
Most discussed in
Behavior of the Lower Organisms, 1906
In the library
804 passages in 27 works
Rewritten
2026-10-03
18501875190019251950197520002025Binet, A., 18881Morgan, T. H., 19012Morgan, T. H., 19013Jennings, H. S., 19064Driesch, H., 19085Child, C. M., 19156Baluška F, Levin M, 20167Silic MR, Zhang G, 20238Fábregas-Tejeda A, Sims M, 20259
01

Early observations

Binet, in 1888, argued that protoplasmic masses, the amoeba above all, have a viscous and elastic outer layer and a liquid interior carrying granules.1 He held that the liquid is passive. It enters a pseudopod because it meets less resistance there. Jennings, in 1906, described how Paramecium and Stentor feed. In Stentor, prey are caught in the ciliary vortex, carried to the buccal pouch, and taken through the mouth into the internal protoplasm.4 Both authors described the whole act from the behaviour of one cell.

02

Nucleus and regeneration

Cutting cells into pieces showed what a fragment needs to survive. Nussbaum cut the ciliates Oxytricha and Gastrostyla, and pieces holding part of the nucleus regenerated a smaller whole organism.2 Gruber found the same in Stentor coeruleus. Pieces without a nucleus closed over the cut and moved about for a time, but they died.3 Child, in 1915, followed the death of Stentor in cyanide and showed that disintegration ran along the body axis in a regular order.6

03

Action or mere reaction

Authors disagreed over how to read such behaviour. Driesch, in 1908, held that a run of changing reactions to one repeated stimulus, which Jennings had found in Stentor, never deserves the name of real acting.5 He allowed fatigue as one possible cause. Silic and Zhang report that the first intracellular measurements of a resting membrane were made in Paramecium in 1934.7

04

Modern work

Baluška and Levin, in 2016, discussed a model of Dictyostelium amoebae in which a new pseudopod makes the local cortex more excitable while new pseudopods elsewhere are inhibited.8 They noted that this model carries a memory of earlier pseudopod positions.8 Fábregas-Tejeda and Sims, in 2025, cite work on Stentor coeruleus and the slime mould Physarum as evidence that habituation does not require neuronal processing.9 They treat as open whether the molecular storage of memory is shared between neuronal and non-neuronal organisms.9

SourcesEach quotation was checked word for word against the passage it opens.
  1. All protoplasmic masses, and especially the amoeba, consist of two parts, an enveloping membrane or ectosarc, viscous and elastic, and the central liquid contents holding granules in suspension.Binet, A., 1888 · The Psychic Life of Micro-organisms: A Study in Experimental Psychology · open at passage 32
  2. Nussbaum ('84, '86) cut into pieces the ciliate infusoria, oxytricha and gastrostyla. Those pieces that contained a nucleus quickly regenerated a new whole organism of smaller sizeMorgan, T. H., 1901 · Regeneration · open at passage 162
  3. Gruber obtained the same result on another ciliate infusorian, Stentor ccernleus. He found that, although the non-nucleated pieces close over the cut-surface, and move about for some time, they eventually die.Morgan, T. H., 1901 · Regeneration · open at passage 162
  4. Such animals are caught in the strong ciliary vortex, carried to the buccal pouch, which often contracts in such a way as to prevent their escape, and are then taken through the mouth into the internal protoplasm.Jennings, H. S., 1906 · Behavior of the Lower Organisms · open at passage 515
  5. a mere consecutive line of changes of reactions in response to one and the same often repeated stimulus, as discovered by Jennings in the Protozoon Stentor and in the earthworm, never deserves the name of real actingDriesch, H., 1908 · The Science and Philosophy of the Organism · open at passage 239
  6. Figs. 3-7 show the course of death and disintegration along the axis in Stentor coendeiis, one of the common infusoria.Child, C. M., 1915 · Individuality in Organisms · open at passage 99
  7. In this model, the appearance of a pseudopod makes the local cortex temporarily more excitable (a kind of potentiation), while globally new pseudopods are inhibited.Baluška F, Levin M, 2016 · On Having No Head: Cognition throughout Biological Systems · open at passage 20
  8. The first intracellular electrical measurements of the resting membrane in the protozoon Paramecium were performed in 1934 [29].Silic MR, Zhang G, 2023 · Bioelectricity in Developmental Patterning and Size Control: Evidence and… · open at passage 4
  9. have provided evidence that habituation (a simple form of learning) does not require neuronal processing.Fábregas-Tejeda A, Sims M, 2025 · On the prospects of basal cognition research becoming fully evolutionary… · open at passage 31
Linked ideas
Regenerationrelated to
Morgan and Verworn report that nucleated pieces of Stentor and other protozoa regenerate into whole cells.
Child describes a susceptibility gradient along the axis of a single Stentor cell, using cyanide disintegration.
Fábregas-Tejeda and Sims cite habituation in Stentor as learning that needs no neurons, a memory case outside nervous systems.
Levin (2025) uses the amoeba's small cognitive light cone to frame cancer as cells reverting to unicellular goals.
Manicka and Levin move from single-cell memory and decisions to tissues detecting the difference from a correct form.
Trial and errorrelated to
Jennings builds the idea from the movements of Paramecium and Amoeba, and compares how effective their differing movements are at escaping unfavourable conditions.
Tropismrelated to
Loeb offers tropisms as elements for a mechanistic account of animal behaviour, the same ground Jennings's trial-and-error work covers.
Jennings's work on lower organisms supplies the behavioural evidence, while he argues it cannot decide whether consciousness is present.
Binet and Jennings describe infusorian food habits that change with the medium, an early case of behavioural plasticity.
Basal cognitionrelated to
Single cells and other aneural organisms are cited as showing memory, prediction and learning without a nervous system.
Collective intelligence of cellsprecursor of / follows
Levin says cells derive from unicellular ancestors with rich behavioral repertoires; Verworn and Jennings describe swarm-spore responses to light.
Lotka's amoeba is his doubtful case: purposive or mechanistic cannot be settled while its working is unknown.
Jennings's infusoria show reactions to chemicals that vary with the past and present conditions of the individual.
Galvanotaxispart of / contains
Galvanotaxis is one single-cell response: Paramecium, Polytoma and Pleuronema swim toward or away from the kathode, and Amoeba contracts at the anode. Driesch calls it real taxis amongst Infusoria.
Metabolism and cell fateprecursor of / follows
Jennings made metabolic state the main determinant of reactions in simple organisms, an early form of the idea.
Loeb applies the same heliotropism experiments to Volvox, and Evangelidis et al. report gravisensitivity and geotropism in Physarum.
Physarum is a single cell whose foraging and choices are described in the held passages, so it is a unicellular case.
Physical forces and formprecursor of / follows
Verworn's surface-tension picture of amoeboid motion is an early physical account of single-cell movement.
Resting membrane potentialprecursor of / follows
Resting membrane potential was first measured inside a single cell in Paramecium.
Lyon describes bacteria judging signals against their own internal milieu.
Binet and Jennings tie the movements of bacteria and infusorians to light and to oxygen produced by chlorophyll.
Where it is discussedPassages matching Paramecium, infusoria, amoeba, Stentor
1906Behavior of the Lower Organisms · Jennings, H. S.398
1899General Physiology: An Outline of the Science of Life · Verworn, M.158
1888The Psychic Life of Micro-organisms: A Study in Experimental Psychology · Binet, A.75
1908The Animal Mind: A Textbook of Comparative Psychology · Washburn, M. F.30
1992On Growth and Form · Thompson, D. A. W.30
1915Principles of General Physiology · Bayliss, W. M.19
1908The Science and Philosophy of the Organism · Driesch, H.18
1901Regeneration · Morgan, T. H.17
1924Physiological Foundations of Behavior · Child, C. M.16
1925Elements of Physical Biology · Lotka, A. J.8