More evidence suggests self-awareness is also for some fish
Date:
February 17, 2022
Source:
Osaka City University
Summary:
Researchers address criticisms to previous work by providing
additional evidence to suggest the cleaner fish Labroides dimidiatus
has Mirror Self-Recognition.
FULL STORY ==========================================================================
An international team of researchers respond to criticisms on previous
work that demonstrated Mirror Self-Recognition (MSR) in the cleaner fish Labroides dimidiatus, by 1) successfully repeating the mark test with
a larger sample size, 2) showing the MSR behaviour to be the visual
result of the mark not a physical response to it, and 3) showing that MSR-trained fish do not show aggression to spatially varied mirror
images of themselves. Additionally, they further demonstrate potential self-awareness in L. dimidiatus by showing that they do not demonstrate
MSR behaviour when visually presented with the mark on other fish and
solidify the importance of ecologically relevant marks presented in
previous work by showing MSR behaviour of L. dimidiatus with brown marks,
meant to resemble a main food source of the fish, as opposed to no such behaviour in fish with green or blue marks.
========================================================================== Mirror Self-Recognition (MSR) is seen as evidence for self-awareness and passing the mark test, in which animals touch or scrape a mark placed on
their body in a location that can only be indirectly viewed in a mirror,
is used to determine the capacity of an animal for MSR. Aside from
chimpanzees, the evidence for other animals having passed the mark test
has been criticized and thus inconclusive. By addressing criticisms placed against their previous work on the cleaner fish Labroides dimidiatus,
an international team of researchers led by Masanori Kohda from the
Graduate School of Science, Osaka City University, has provided further evidence to suggest the fish have the capacity for MSR.
This new experiment was recently published in PLOS Biology.
"Previously, using a brown marking on the throat area of L. dimidiatus,
we had shown 3 out of 4 cleaner fish to scrape their throats several
times after swimming in front of a mirror," states Professor Kohda,
"a number on par with similar studies done on other animals like
elephants, dolphins, and magpies." However, one of the criticisms laid
against this result was sample size and the need for repeated studies
showing positive results. Teaming up with researchers from the Max Planck Institute of Animal Behaviour in Germany and the University of Neucha^tel
in Switzerland, this study increased the sample size to 18 cleaner fish,
with a 94% positive result of 17 of them demonstrating the same behaviour
from the previous study.
But why a brown mark? "After looking at similar studies done on monkeys,
pigs, dogs, cats, etc. that clearly tested negative, we wondered if the
reason these animals didn't attend to the mark was because it didn't
represent something in their natural environment they would be concerned about," says Prof. Kohda. "In our previous study, we used a brown mark
as it may look like a small parasite that is a main food source for
L. dimidiatus." A criticism in response to this was the possibility that
the physical sensation of the mark, together with seeing the brown mark
in the mirror, may trigger behaviour that doesn't conclusively suggest
MSR. To address this, the team tested how the fish would respond to a
physical stimulus in their throat by injecting the brown mark 3mm deep
(as opposed to 1mm). At such a depth the mark was hardly visible, yet
they found that fish with the deeper injection scraped their throat
at similar rates, whether a mirror was absent or present. To further
solidify the importance of using marks that are ecologically relevant
to the animals in MSR studies, the team found that no fish injected with
green or blue marks demonstrated the scraping behaviour.
Lastly, some criticisms wondered if L. dimidiatus recognized the
mirror image as itself and not another fish. A mirror-trained animal
is one that is introduced to a mirror image of itself and goes through
3 steps. First it expresses some kind of aggressive behaviour as it
likely perceives the mirror- image as another animal, then it shows
unnatural, yet non-aggressive movement, as it confirms the mirror image
is not another animal, and last it repeatedly looks at its own body
with no aggression. At this point MSR is possible as it can now see
the mark and try to scrape it off. "Our previous study demonstrated
MSR in L. dimidiatus," says Prof. Kohda, "however studies with other
animals have shown that simply moving a mirror reignites aggressive
behaviour suggesting the animal has only learned a spatial contingency,
not MSR." To address this, the team transferred mirror-trained cleaner
fish to a tank with a mirror on one side of the tank and then 3 days
later to a tank with a mirror on the other side and saw the fish show
no aggression towards their mirror image in both tanks.
Also, to ensure the L. dimidiatus that passed the mark test truly are recognizing themselves, they placed mirror-trained fish in adjacent
tanks that were separated by transparent glass. After 2-3 days when
fish largely reduced their aggressive behaviour towards each other,
they were marked the standard way the following night. None of the
fish scraped their throat during the 120 mins of exposure to each other
the following morning. "This result suggests that a visual ecologically relevant stimulus on another fish is not enough to induce throat scraping
on marked subjects," says Prof. Kohda. "We still have much work to be
done, especially quantitatively, to show that fish, as well as other
animals have the capacity for MSR, however as a result of this study we reiterate the conclusion of our previous study that either self-awareness
in animals or the validity of the mirror test needs to be revised." ========================================================================== Story Source: Materials provided by Osaka_City_University. Note: Content
may be edited for style and length.
========================================================================== Related Multimedia:
* Fish_looking_at_a_mirror ========================================================================== Journal References:
1. Masanori Kohda, Shumpei Sogawa, Alex L. Jordan, Naoki Kubo, Satoshi
Awata, Shun Satoh, Taiga Kobayashi, Akane Fujita, Redouan
Bshary. Further evidence for the capacity of mirror
self-recognition in cleaner fish and the significance of
ecologically relevant marks. PLOS Biology, 2022; 20 (2): e3001529
DOI: 10.1371/journal.pbio.3001529
2. Masanori Kohda, Takashi Hotta, Tomohiro Takeyama, Satoshi Awata,
Hirokazu
Tanaka, Jun-ya Asai, Alex L. Jordan. If a fish can pass the mark
test, what are the implications for consciousness and self-awareness
testing in animals? PLOS Biology, 2019; 17 (2): e3000021 DOI:
10.1371/ journal.pbio.3000021 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/02/220217141331.htm
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