Are insects conscious?

I recently discovered an intriguing publication investigating the intellectual faculties of ants. In “Are Ants (Hymenoptera, formicidae) capable of self recognition?” Marie-Claire and Roger Cammaerts claim that ants are able passing the mirror test – a technique intended to assess cognitive self-awareness in animals [1]. The animal is marked on its body with a coloured dot and put in front of a mirror. If the subject tries to investigate the spot on itself, that is seen as a sign of self-recognition. An animal that is unable to identify itself might assume the mirror image depicts a conspecific and could try to attack it or exhibit avoidance behavior. There is a long list of otherwise quite intelligent animals, such as rhesus macaques, grey parrots or cats, that have failed the test, so this result seems quite extraordinary. I found the methodology pretty sound, however, the journal is a bit dodgy and discussion has arisen about the legitimacy of the results (see for example the discussion on Wikipedia here or here a blog entry by author and biologist Peter Watts). I have not found any attempt to replicate this exact experiment, so this is a bit of a dead-end. However, the paper got me thinking about whether insects might possess some form of consciousness. This article is dedicated to investigating this topic.

To give a meaningful answer to the question, “consciousness” needs to be defined. Examining this issue rigorously is the topic of dissertations and beyond the scope of this essay. Here, I am using the definition proposed by the philosopher Thomas Nagel in his famous article “What is it like to be a bat?” [2].

But no matter how the form may vary, the fact that an organism has conscious experience at all means, basically, that there is something it is like to be that organism. There may be further implications about the form of the experience; there may even (though I doubt it) be implications about the behavior of the organism. But fundamentally an organism has conscious mental states if and if only there is something that it is like to be that organism – something it is like for the organism.

This approach is echoed in “What insects can show us about the origins of consciousness”, which makes a strong case for insect consciousness [3]. The authors, Andrew B. Barron and Colin Klein, rely mainly on a theory developed by the Swedish-American neuroscientist Björn Merker that designates the human midbrain and not, as sometimes assumed, the cortex as the origin of consciousness. The midbrain is the place where, in mammals, the body is simulated spatially within its surroundings. This enables the animal to consider things not captured by its senses such as a piece of food under a leaf. Additionally, the midbrain also “makes decisions” when there are competing desires or preferences. Insect brains all share a common structure that centers around the central complex. The authors propose that this area is functionally analogous to a midbrain and enables the representation of visual space. They strengthen their case by citing evidence that insects have the capacity for selective attention and give examples of behaviors that go beyond simple mechanical processes. Interestingly, the authors also expand their theory to assess which animals don’t have consciousness. The roundworm C. elegans is able to memorize things, however, there is no evidence that it can model itself spatially – which is a requirement according to Barron’s and Klein’s argument.  Their conclusion has been criticized by various authors. The main point of contention is whether the cortex is needed to generate a subjective experience [4]. Key argues that some form of high-level representations are needed for this and that assessing capacity for consciousness is not possible by comparing the insect and vertebrate brains [5].

Mallat, Jon and Feinberg state that consciousness is not confined to a single brain area but might be widely distributed. They also attack Merker’s claim that consciousness originates in the midbrain [6]:

To this day, the dominant paradigm in consciousness studies is that primary consciousness of mapped mental images in mammals comes from the cerebral cortex or from interactions between the cortex and the thalamus, not from the superior colliculus/tectum as Merker claims. […]

Medical neuroimaging and brain-lesion studies strongly support cortical consciousness when the results are interpreted in the most direct and straightforward way: damage to the cortex leads to loss of some sensory consciousness (Boly et al., 2013; Feinberg, 2009). Destruction of the visual, occipital, cortex causes blindness in primates.

I am not qualified in any way to weigh in on this disagreement and therefore must look somewhere else to try to answer this question for myself.

One such method is an appeal to authority. Peter Singer, possibly the world’s best-known animal rights philosopher, ponders the thesis in a blog post on the basis of the article by Barron and Klein. He concludes that, while insect consciousness, is far neither certain nor impossible, it is worth considering. However, before any insect rights campaigns are launched, we should do more to prevent the suffering of vertebrates – which we know are able to do so.

This thought marks the end of this essay. While I would have loved to learn more about the topic, the sources were sparse and the disagreements too strong for a noob like me to draw any firm conclusions. However, this project got me interested in what it means to be conscious  and I am looking forward to go deeper into this issue.

References

[1] Cammaerts, M.-C., & Cammaerts, R. (2015). ARE ANTS (HYMENOPTERA, FORMICIDAE) CAPABLE OF SELF RECOGNITION? Journal of Science, 5(7).

[2] Nagel, T. (1974). What Is It Like to Be a Bat? The Philosophical Review, 83(4), 435–450. https://doi.org/10.2307/2183914

[3] Barron AB, Klein C. What insects can tell us about the origins of consciousness. Proc Natl Acad Sci U S A. 2016 May 3;113(18):4900-8. doi: 10.1073/pnas.1520084113. Epub 2016 Apr 18. PMID: 27091981; PMCID: PMC4983823.

[4] Allen-Hermanson, Sean. (2016). Is cortex necessary?. Animal Sentience. 1. 10.51291/2377-7478.1137.

[5] Key, B. (2016). Phenomenal consciousness in insects? A possible way forward. Animal Sentience, 1(9). https://doi.org/10.51291/2377-7478.1159

[6] Mallatt, J., & Feinberg, T. E. (2016). Insect consciousness: Fine-tuning the hypothesis. Animal Sentience, 1(9). https://doi.org/10.51291/2377-7478.1141