Study
Associative learning in the box jellyfish Tripedalia cystophora
Bielecki, Jan; Nielsen, Sofie K. D.; Nachman, Gösta; Garm, Anders
Current Biology, 2023
Box jellyfish were placed in a circular arena patterned with grey and white stripes simulating mangrove roots at varying apparent distance. Contrast was manipulated so that the animals initially misjudged distance and collided, and their pivot-turn responses were measured over successive minutes.
- Studied in
- Tripedalia cystophora
- Sample size
- box jellyfish tested in patterned arenas
Within a few minutes the animals increased their distance from the wall and increased successful avoidance turns, adjusting behaviour to the altered contrast. The change required pairing of the visual stimulus with the mechanical consequence of a collision, which is the structure of associative learning rather than habituation.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Associative learning is present in an animal with no centralised brain, indicating that the capacity does not require a central nervous system of the kind previously assumed.
How NatureHQ reads it
The importance here is not that a jellyfish is clever. It is that a nervous system of about a thousand neurons, arranged as four separate visual processing centres with no brain joining them, is enough for a form of learning that had been treated as requiring one. That is a claim about what brains are *for*, made by removing the brain and finding some of the function still there.
- One species, small numbers, and a short observation window.
- The learning demonstrated is specific and simple; nothing here speaks to memory beyond minutes.
- Distinguishing associative learning from sensitisation in an animal this unlike us is genuinely difficult, and the design addresses it rather than settling it.
Moving the goalposts on an animal with no brain
Box jellyfish steer around mangrove roots using vision. Can an animal with about a thousand neurons and no brain learn, or is that steering a fixed reflex?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: Cell PressPublished in a Cell Press journal.
doi.org/10.1016/j.cub.2023.08.056
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-11.