It looks like that ant-self recognition study should have been published somewhere better—it could be better presented and is missing some controls, but otherwise seems sound and was done by two established researchers.
I’m personally much more skeptical of the work. Most notably, the paper’s results are suspiciously clear-cut—all the of treated ants showed the mirror test behavior and none of the control ants did. Generally mirror self-recognition tests are not this straightforward and it is common, even with chimps, for some tested subjects to not pass. Unless ants are potentially smarter than chimps, I don’t think we should expect results this clear. Instead, this suggests something in the study may have gone wrong.
Also Max Carpendale, then a contract researcher with Rethink Priorities, pointed out to me that one of the authors of the paper, Marie-Claire Caemmarts, has a history of making dubious claims outside mainstream scientific consensus. For example, she has published research that suggests cell phone radiation and Wi-Fi are damaging to human health, for which she has received criticism of bad science.
Thanks for the comments Peter and Michael. I’m not very familiar with the mirror test in general so I can’t comment with confidence about how well this compares to the results with other species. But after having looked back at Table 2 in the paper reporting the mirror test results I’d argue the results aren’t so clear cut—one ant never cleaned itself, whereas the other ants cleaned themselves between 1 and 9 times over the six minute trial (also, the behaviour never occured in juvenile ants). I don’t think this indicates that ants are smarter than chimps, another explanation is simply that, assuming cleaning occurs because the ants visually recognised the paint spot from their reflection, that this triggered a reflexive grooming behaviour. Chimps probably have more complex motivations—if they see the paint spot some may want to remove it, but others might not be in the mood for cleaning or could enjoy having it there. If the difference is then between reflexive ant cleaning vs. voluntary chimp cleaning you could then go onto discuss the relevance of each type of behaviour for demonstrating self-recognition, but I don’t think we are there yet.
Admittedly, this study was not performed rigorously. The review Michael links to (Gallup 2018) presents some important criticism. The ants also could have perceived the paint through mechanosensory hairs on their head—although the difference in grooming between brown and blue paint seems to suggest this wasn’t the case. Another point is that this study doesn’t really define what was considered cleaning behaviour, and it may be that the threshold for this was lower than that used in by chimp researchers, raising the likelihood of false positives for the ants. In addition to clear monitoring of the ant grooming pre-, during, and post- mirror exposure, it would also be useful to do a recovery experiment whereby the blue paint was covered with brown paint—if this prevented later grooming behaviour it would strongly suggest that the grooming was related to the ants visual perception of its reflection.
It’s also a fair point that both Caemmarts do not perform very rigorous research studies and generally publish them in lowly ranked to predatory journals. Publishing in low ranked journals isn’t a crime in itself, although the peer review usually isn’t very rigorous and I wouldn’t be surprised if these authors simply keep submitting the same manuscript to a journal until one will take it without revisions (this is poor scholarship but not uncommon). However, it does present a bit of problem if the first report on a controversial topic (invertebrate self-recognition) comes out like this—it probably didn’t get much attention from other ant cognition researchers (there might not be many anyway), and a simple replication study can’t be published in highly ranked journal (if the results held up and the study was done well I think this would have made it into mid to top ranked generalist journal).
In reality, this is a pretty simple experiment to replicate with ants. I know a few ant navigation researchers in Europe who could easily supervise a student to replicate it over summer (the Myrmica genus is quite common). I can put you in contact if this is a useful point for RP to confirm for the invertebrate sentience project? I’d also wager $50 that this does replicate, insofar that the ants groom paint spots based on their reflection but besides any interpretation of self-awareness based on this result.
Hey Gavin, we (at Rethink Priorities) would be interested in exploring funding for this. Would you be able to reach out to peter@peterhurford.com and we can discuss next steps?
After hearing opinions about the Cammerts from another academic who knows them‚ I’ve unfortunately become a lot less confident that this study could replicate.
Is the report by Cammaerts and Caemmaerts (2015) positive evidence of self-recognition in ants? Our answer is an emphatic no. Too many crucial methodological details are not given. No formal period between marking the subjects and then exposing them to the mirror was included; the reader is simply asked to accept that no self-cleaning movements occurred before marked ants first saw themselves in the mirror and that marked ants without any mirror did not do so. There is no clear mention of how these data were collected. Were the ants recorded on video? Were they observed directly? In other studies of ant behavior some means of magnification are used, but Caemmerts and Cammaerts provide no information about this, and it is not even clear if any attempt to assess inter-observer reliability was made.
It also remains a possibility that responses to the mirror on the mark test were confounded by chemical cues from the ant’s antennae and chemoreceptors on the mandibles. For instance, if the blue dye was chemically different from the brown dye, chemoreception could explain why ants marked with blue dye were more likely to be attacked by other ants. It is also important to note that the ants must have sensed that they had the marks on themselves through these and other olfactory channels prior to being exposed to the mirror, which would invalidate the mark test.
Notwithstanding the absence of evidence for vision-based individual facial recognition in ants, it would be astonishing if such poorly sighted, small brained insects − especially those without any mirror experience − could immediately use their reflection to try to remove a freshly applied foreign mark that was only visible in the mirror
It looks like that ant-self recognition study should have been published somewhere better—it could be better presented and is missing some controls, but otherwise seems sound and was done by two established researchers.
I’m personally much more skeptical of the work. Most notably, the paper’s results are suspiciously clear-cut—all the of treated ants showed the mirror test behavior and none of the control ants did. Generally mirror self-recognition tests are not this straightforward and it is common, even with chimps, for some tested subjects to not pass. Unless ants are potentially smarter than chimps, I don’t think we should expect results this clear. Instead, this suggests something in the study may have gone wrong.
Also Max Carpendale, then a contract researcher with Rethink Priorities, pointed out to me that one of the authors of the paper, Marie-Claire Caemmarts, has a history of making dubious claims outside mainstream scientific consensus. For example, she has published research that suggests cell phone radiation and Wi-Fi are damaging to human health, for which she has received criticism of bad science.
Thanks for the comments Peter and Michael. I’m not very familiar with the mirror test in general so I can’t comment with confidence about how well this compares to the results with other species. But after having looked back at Table 2 in the paper reporting the mirror test results I’d argue the results aren’t so clear cut—one ant never cleaned itself, whereas the other ants cleaned themselves between 1 and 9 times over the six minute trial (also, the behaviour never occured in juvenile ants). I don’t think this indicates that ants are smarter than chimps, another explanation is simply that, assuming cleaning occurs because the ants visually recognised the paint spot from their reflection, that this triggered a reflexive grooming behaviour. Chimps probably have more complex motivations—if they see the paint spot some may want to remove it, but others might not be in the mood for cleaning or could enjoy having it there. If the difference is then between reflexive ant cleaning vs. voluntary chimp cleaning you could then go onto discuss the relevance of each type of behaviour for demonstrating self-recognition, but I don’t think we are there yet.
Admittedly, this study was not performed rigorously. The review Michael links to (Gallup 2018) presents some important criticism. The ants also could have perceived the paint through mechanosensory hairs on their head—although the difference in grooming between brown and blue paint seems to suggest this wasn’t the case. Another point is that this study doesn’t really define what was considered cleaning behaviour, and it may be that the threshold for this was lower than that used in by chimp researchers, raising the likelihood of false positives for the ants. In addition to clear monitoring of the ant grooming pre-, during, and post- mirror exposure, it would also be useful to do a recovery experiment whereby the blue paint was covered with brown paint—if this prevented later grooming behaviour it would strongly suggest that the grooming was related to the ants visual perception of its reflection.
It’s also a fair point that both Caemmarts do not perform very rigorous research studies and generally publish them in lowly ranked to predatory journals. Publishing in low ranked journals isn’t a crime in itself, although the peer review usually isn’t very rigorous and I wouldn’t be surprised if these authors simply keep submitting the same manuscript to a journal until one will take it without revisions (this is poor scholarship but not uncommon). However, it does present a bit of problem if the first report on a controversial topic (invertebrate self-recognition) comes out like this—it probably didn’t get much attention from other ant cognition researchers (there might not be many anyway), and a simple replication study can’t be published in highly ranked journal (if the results held up and the study was done well I think this would have made it into mid to top ranked generalist journal).
In reality, this is a pretty simple experiment to replicate with ants. I know a few ant navigation researchers in Europe who could easily supervise a student to replicate it over summer (the Myrmica genus is quite common). I can put you in contact if this is a useful point for RP to confirm for the invertebrate sentience project? I’d also wager $50 that this does replicate, insofar that the ants groom paint spots based on their reflection but besides any interpretation of self-awareness based on this result.
Hey Gavin, we (at Rethink Priorities) would be interested in exploring funding for this. Would you be able to reach out to peter@peterhurford.com and we can discuss next steps?
After hearing opinions about the Cammerts from another academic who knows them‚ I’ve unfortunately become a lot less confident that this study could replicate.
There’s some criticism here:
Hi MichaelStJules! We’ll consider that paper for a clarificatory commentary on this. Thanks again for your suggestions!