Neuroscientist Giorgio Vallortigara ponders the mystery of how exactly babies quickly recognize things when they are born — like human faces — that they simply cannot have learned. We might call it “imprinting” or “instinct” but that’s just a classification, not an explanation.
The author of Born Knowing (MIT Press, 2021) decided to start with chicks. That’s a bit simpler. Psychology students know, of course, that newly hatched chicks seem to know that they should follow their mother and do what she does. But what specific cues enable them to identify their mother? It turns out, according to his and colleagues’ research, that they are looking for specific geometrical patterns:
Chicks need to actively explore and learn about their environment from the moment they hatch. Therefore, they learn very rapidly to identify and attach to their mother and siblings. For a long time, this imprinting process has been considered a form of exposure learning that is devoid of any constraints. In 1935, Martina the goose famously imprinted on the zoologist Konrad Lorenz – a very implausible mother. However, more recent research has shown that newly hatched chicks are not tabulae rasae: they hatch with predispositions to attend to, and thus to imprint on, particular kinds of stimuli. Before they have ever seen a mother hen, chicks prefer to approach objects that roughly resemble the shape of a mother hen, as originally shown by the neurobiologist Gabriel Horn and his colleagues. In my lab, we found that the configuration of the mother’s head features can be reduced to just an ovoid outline that contains three high-contrast blobs arranged as an inverted triangle – a sort of emoticon with eyes and beak/mouth.Giorgio Vallortigara, “Babies and chicks help solve one of psychology’s oldest puzzles” at Psyche (February 2, 2022) Horn’s paper and one of Vallortigara’s papers require a subscription. However, this one, from 2019, is open access.
In short, they don’t need to know that it is “mommy’s face.” It is a geometric outline that they are scanning for. But how do they know that that is the outline they should seek?
It’s the same with bats:
A new Tel Aviv University study has revealed, for the first time, that bats know the speed of sound from birth. In order to prove this, the researchers raised bats from the time of their birth in a helium-enriched environment in which the speed of sound is higher than normal.
They found that unlike humans, who map the world in units of distance, bats map the world in units of time. What this means is that the bat perceives an insect as being at a distance of nine milliseconds, and not one and a half meters, as was thought until now.Tel Aviv University, “Bats Know the Speed of Sound From Birth” at Neuroscience News (May 8, 2021)
But the key takeaway point is that the bats do not actually learn this information. They were born knowing it. When the researchers, led by Prof. Yossi Yovel, head of the Sagol School of Neuroscience at Tel Aviv University, manipulated the bats’ learning environment via helium so as to increase the speed of sound, both adults and pups landed, off target, in front of the intended insect prey. Post-birth learning had made no difference and the error could not be corrected.
Some explanations sound frustrating:
”Because bats need to learn to fly within a short time of their birth,” explains Prof. Yovel, “we hypothesize that an evolutionary ‘choice’ was made to be born with this knowledge in order to save time during the sensitive development period.”Tel-Aviv University, “Bats know the speed of sound from birth, scientists discovery” at ScienceDaily (May 5, 2021) The paper is open access.
But there is a logical fallacy here. Of course it is an advantage for the bat pup to be born with the ability to do speed-of-sound calculations. But how, exactly, is that advantage obtained? It would be an advantage, for example, for every child to be born with the ability to do calculus. But no path appears to exist for most children to make that happen. So it doesn’t.
That said, babies are born knowing some things, but that knowledge wanes. And this is where Vallortigara’s research gets really interesting:
The same kind of preference was subsequently discovered in human neonates, as the cognitive neuroscientist Mark Johnson and colleagues showed, based on the newborns’ eye gaze. Recently, my team used EEG to measure electrical activity in the brains of newborns as they saw face-like, inverted face-like, or scrambled face-like configurations, and we found impressive selectivity of response to the first pattern. That is, we observed a significantly stronger change in our measure of cortical activity in response to the upright face-like stimuli, as compared with the other stimuli. We also revealed the involvement of cortical areas that overlap with the adult face-processing circuit. Our findings suggest that the cortical route specialised for face processing is already functional at birth.Giorgio Vallortigara, “Babies and chicks help solve one of psychology’s oldest puzzles” at Psyche (February 2, 2022)
Babies (and chicks) also preferred biological motion to mechanical motion. But how did they know? Now here’s what happens with the babies:
It’s interesting to note that these life-detecting abilities appear to wax and wane as babies age. For instance, the preference for biological motion seems to vanish at one and two months of age in human infants, and then to reappear by three months. A likely explanation is that, at birth, animals possess innate mechanisms that act in a reflex-like manner, serving to direct their attention to relevant stimuli in the environment, such as caregivers. Then a second mechanism, based on learning, might take precedence, allowing more specific recognition – ie, the face of Mom as opposed to a stranger, or the movement of one’s own species as opposed to generic biological motion, and so on.Giorgio Vallortigara, “Babies and chicks help solve one of psychology’s oldest puzzles” at Psyche (February 2, 2022)
So there are two stages in babies’ recognition of other humans; one is innate and covers the first months of life after birth, gradually waning in favor of the second, which is learned. That may have implications for the detection and early treatment of autism spectrum disorder (ASD):
The diagnosis of ASD cannot be performed before two to three years of age, and we know that an early diagnosis would be extraordinarily valuable, enabling prompt psychological and social interventions. Differences in animacy detection could potentially be of aid in such a diagnosis. Using the behavioural techniques we developed for animacy detection, we tested newborns with an increased likelihood of ASD (ie, those who have an older sibling diagnosed with ASD). We found that these newborns appeared to have deficits in animacy detectors for face-like and biological-motion stimuli, based on looking time. It seems likely that there is a delay in their appearance, as some evidence for canonical preferences does emerge in these babies, but later on, at about four months. A delay in the development of animacy detectors could potentially affect the mutual interaction between an infant and a mother, but more research would be needed to test that hypothesis.Giorgio Vallortigara, “Babies and chicks help solve one of psychology’s oldest puzzles” at Psyche (February 2, 2022)
To try to pinpoint a neurological basis for innate knowledge, Vallortigara’s team looked at the brains of chicks:
By analysing the expression of so-called early genes (which guide the production of certain proteins that can be made visible by colouring them in the cells) we were able to identify tiny regions selectively involved in the preference for face-like stimuli (the nucleus taenia, which is homologous to the lateral part of the mammalian amygdala) and for changes of speed (the lateral septum, a brain area that has remained mostly the same in different classes of vertebrates such as mammals and birds).Giorgio Vallortigara, “Babies and chicks help solve one of psychology’s oldest puzzles” at Psyche (February 2, 2022)
Much more research needs to be done, of course. Meanwhile, if this research holds up, it turns out that both the Nature Party and the Nurture Party are right. Yes, there is an innate program that guides newborns to look for human faces and live body movements. But that it wanes and is replaced by personal learning over the subsequent weeks and months — a design that coincides with the infant’s increasingly complex needs.
You may also wish to read: Source of most animal intelligence still a mystery. Eric Cassell takes questions: If life forms are born or hatched knowing this stuff, it isn’t learned. But if it’s in the genes, where is it? Questions range from “Do animals have free will?” through “How do migratory animals adapt to magnetic poll reversals” which may come every 1000 years or so?