Summary: A new study provides the first empirical evidence that an invertebrate can use a mirror as an abstract spatial tool to interpret its surroundings. Researchers found that the California two-spot octopus (Octopus bimaculoides) can read mirror reflections to locate and intercept prey that is entirely out of its direct line of sight.
By showing that an organism so distantly related to humans can perform this visual task, the research supports the idea that complex spatial cognition can evolve independently in very different branches of life—an example of convergent evolution in neural solutions to ecological challenges.
Key Facts
- First invertebrate demonstration: Mirror use for spatial localization has been documented in some mammals and birds, but this study is the first to show an invertebrate using mirror reflections to infer the location of an occluded object.
- 73% success rate: In training and test trials at Dartmouth’s Octopus Lab, octopuses chose the correct hidden location about 73% of the time when relying on mirror information.
- Virtual prey to isolate vision: To prevent chemosensory or tactile cues from influencing behavior, the experiment used a projected virtual crab visible only via the mirror so animals had to rely on vision and spatial inference.
- 180-degree navigation response: When a virtual crab was projected behind the octopus and visible only in a frontal mirror, the animals did not attack the reflection. Instead they turned 180 degrees or climbed overhead to reach the actual projection site and obtain a live food reward.
- Faster spatial planning over time: Overhead tracking of a point between the eyes on the mantle showed that octopuses did not always take the shortest path but became quicker and more efficient at reaching the hidden stimulus as training progressed.
- Evidence for convergent evolution: Lead author Mary Kieseler notes that humans and octopuses diverged from a distant common ancestor hundreds of millions of years ago; the independent emergence of mirror-mediated spatial ability points to convergent evolution of cognitive strategies.
- Internal map hypothesis: Senior author Peter Tse interprets the behavior as consistent with an internal spatial representation—an internal map that links reflected information with real-world coordinates, useful for hunting in complex marine habitats.
Source: Dartmouth College
Octopuses are known for notable intelligence—Inky the Octopus’s escape from the National Aquarium of New Zealand in 2016 being a well-known example.
The new Dartmouth study demonstrates that octopuses can use mirror reflections to find food that is out of view, revealing a previously undocumented form of spatial cognition in an invertebrate. The findings are published in the journal Current Biology.
“These experiments are the first to show that invertebrates can use mirrors to interpret their environment and locate prey,” says lead author Mary Kieseler, who completed the work as a PhD student in Dartmouth’s Department of Psychological and Brain Sciences and is now a postdoctoral researcher. “Mirror-mediated localization has previously only been documented in a subset of vertebrates.”
Researchers trained three California two-spot octopuses (Octopus bimaculoides) to refrain from attacking a prey image in a mirror and instead to infer and move to the real location of the hidden stimulus behind them. Training began with acclimation to the mirror followed by a live-reward task in which a crab placed in a jar was visible in the reflection; to obtain that crab, the octopus had to navigate a 90-degree turn and reach the hidden reward.
Because octopuses possess sensitive chemoreceptors that allow them to detect chemical cues through touch, the researchers used a projected virtual crab during critical trials so the animals could not rely on smell or taste. The virtual crab was projected onto the tank wall behind the octopus and visible only via a frontal mirror. The animal started in an open-top start box facing the mirror. Rather than attacking the mirror image, the octopuses turned away or climbed over the box to reach the projection site and receive a live crab as a reward.
Overall, the octopuses selected the correct side about 73% of the time. Motion tracking of a point between the animals’ eyes from overhead allowed the team to analyze paths and timing. Although the octopuses did not always pick the shortest route, they became faster and more consistent at locating the hidden stimulus with experience.
“We don’t enter the world knowing how to use a mirror; we learn it,” says senior author Peter Tse, professor of psychological and brain sciences. “Like a new driver learning to use a rearview mirror, octopuses learned to interpret mirror reflections to infer where objects are located in space.”
The habitats octopuses occupy—coral reefs and complex seafloor terrains—pose navigational and predation challenges. Fast, accurate localization of prey reduces the risk of becoming prey. Tse notes that effective hunters benefit from mental maps of their surroundings; these experiments suggest octopuses may form internal spatial representations that map reflected images onto real-world coordinates, although the authors emphasize that further research is needed to confirm the extent of these internal maps.
Key Questions Answered:
A: Octopuses have strong chemosensory abilities on their skin, so a live crab could be detected by chemical or tactile cues. A projected digital image visible only via the mirror forced the animals to rely exclusively on visual inference and spatial reasoning.
A: Instead of approaching the visible reflection, the octopus inferred the true location of the prey behind it and executed a full 180-degree turn or climbed over the enclosure to reach the occluded projection site, indicating that it linked the reflected image to a separate physical location.
A: The behavior supports the idea of convergent evolution: octopuses and humans diverged from a common ancestor hundreds of millions of years ago, yet both lineages appear to have evolved similar cognitive solutions—such as mirror-mediated spatial inference—to navigate complex environments.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full by the editorial team.
- Additional explanatory context was provided by staff for clarity.
About this neuroscience research news
Author: Amy Olson
Source: Dartmouth College
Contact: Amy Olson – Dartmouth College
Image credit: Mary Kieseler
Original Research: Closed access. “Octopus bimaculoides can learn to utilize a mirror to localize a reward outside the line of sight” by Mary Kieseler, Marvin R. Maechler, Kelly R. Finn, Carl Harris, Jay Michael Vincelli, Zachary Hoffman, Navneet Dhanoa, Jean Fang, Scott Gies, James McHugh, III, Julia Valenti, Mira Ram, John O. Fitzgerald, Madison Augusto, David Edelman, and Peter U. Tse. Current Biology
DOI: 10.1016/j.cub.2026.05.012
Abstract
Octopus bimaculoides can learn to utilize a mirror to localize a reward outside the line of sight
Mirror-mediated localization of hidden objects is well established in some vertebrates but had not been demonstrated in invertebrates prior to this study. Using a mirror to locate occluded items is a form of mediated perception that links a visible reflection to a real, but hidden, spatial location and is considered by some researchers to be a step toward more advanced mirror-related cognition.
Cephalopods offer a compelling test case for convergent cognition. After diverging from a distant common ancestor more than 500 million years ago, cephalopods independently evolved complex perceptual and cognitive abilities that in some respects resemble those of mammals. They also typically react to mirror images as if they were other individuals. In these experiments, a virtual crab visible only in a mirror was projected onto a tank wall. Three Octopus bimaculoides were trained to go to the projection site rather than the mirror itself.
All three octopuses learned the task, selecting the correct side in roughly 73% of trials. Crucially, they sometimes inhibited a direct approach to the salient reflection and instead moved away from the mirror—climbing over chamber walls when necessary—to reach the visually occluded location aligned with the reflected prey. This pattern of behavior suggests both the capacity to inhibit reflexive responses to visible stimuli and the integration of mirror information with a spatial representation of the three-dimensional tank environment.
These results extend mirror-use capabilities to invertebrates and indicate that cephalopods can employ mirror reflections for spatial navigation. The independent evolution of mirror-mediated spatial abilities across diverse taxa suggests that similar cognitive strategies may arise repeatedly when species face comparable ecological navigation challenges.