Studying non-human species, particularly mammals, in a
laboratory setting can be helpful in decoding the incredible complexity of
human speech. Many highly vocalizing species such as songbirds learn the
intricacies of their dialect from their parents. Avian brains, however, are
wired much differently than mammalian brains. In order to more closely
approximate the dynamics of human language learning, studies have been done on
the singing and clicking sounds of whales and dolphins. It would be helpful,
though, to switch to smaller animals that are easier to work with in a
controlled experiment. That is what researchers from Tel Aviv University in
Israel had in mind when they started studying Egyptian fruit bats. Bats show
similar patterns of vocal learning and are easier to manipulate in a laboratory
setting.
Similar to human accents or dialects, young bats learn
distinct patterns of vocalizing from their local population that are
distinguishable from the vocal patterns of bats raised in different colonies.
To demonstrate this, researchers brought 15 pregnant females of the species Rousettus aegyptiacus into a lab and
placed five each into one of three chambers. After all the bats had given
birth, researchers started playing the recorded noises of three different bat
colonies. One chamber received noises that were higher in pitch on average,
another received lower pitched noises, and the last chamber received a mix of
both. After a total of 30 weeks after birth, bats in the high-pitched chamber
made calls that were noticeably higher in frequency than bats in the other two
chambers. In the future, the researchers also plan to release the bats into new
wild colonies to observe whether their dialect remains the same, changes to
match the new colony, or influences the new colony's dialect.
This study points out topics to compare and contrast with
human development. For example, birds usually learn their speech patterns
directly from their parents, whereas the bats did not do so directly. The
unique factor in the bats' speech patterns were instead attributable to their
general environment, similar to the different cultures that humans grow up in.
On the other hand, human families are more isolated by living in different
houses rather than a communal living area, which still allows for cultural
influence but to a slightly lesser degree compared to bats. Knowing these
similarities and differences between humans and other species can help
scientists map out how language developed in the first place in different
evolutionary lines, what parts of the human brain to look at when researching
how the brain processes and produces speech, and what might be the optimal
environment for children to develop high levels of communication. For example,
some parts of the brain may develop in a much more isolated fashion, whereas
other parts of the brain may be much more highly influenced by the social
environment of the individual. This article implies that these more socially
influenced brain pathways would be more directly correlated with the
development of accents, dialects, and perhaps similar forms of communicating
one's thoughts effectively.
In addition to the interesting societal implications, I also
chose this article because I believe the experiment it was based on was
well-controlled. For example, the researchers chose bat mothers that were not
closely related to ensure that the experimental results observed were not due
to genetic differences. In the lab setting there were no random noises or other
stimuli that one might encounter in the wild that could affect the final
results. Instead each chamber was acoustically isolated from the outside world
and from other noises in the lab such as the recordings fed into the other
chambers. The results were also relatively unique. Although it may be intuitive
given how important sound is in such dark environments, it had never been shown
how clearly the speech of newborn bats is influenced by their noisy
surroundings.
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