Source: Radio New Zealand
pixabay
Follow Our Changing World on Apple, Spotify, iHeartRadio or wherever you listen to your podcasts.
Our brains never touch the outside world.
We experience a perception of the world that the brain builds based on all the sensory inputs it receives, as well as existing knowledge.
This is how our sensory systems, like vision, work. We see things because light reflects off a surface and then bounces off the back of our eyeballs, but from there the brain does a lot of work to create an image and fill in the blanks.
These interactions of physical inputs, sensory systems and our brains allow us to develop our sense of self, and how we fit in the world. And this is why neuroscientist Professor Vincent Reid is totally fascinated about where and when this all begins.
Studying sight in the womb
Vincent, now head of the School of Psychological and Social Sciences at the University of Waikato, spent 25 years of his research career investigating how infants learn, including how infants perceive the world through sight. But he realised that he, and others in the field, were working off assumptions.
There was this idea that newborn abilities and preferences in the realm of vision were rapidly acquired directly after birth. But, Vincent thought, could it be possible that these visual abilities and preferences already existed in the womb?
“And so that’s when I started looking at the human foetus and realised that we really didn’t know very much at all about what was going on in the third trimester of pregnancy,” Vincent said.
“Specifically when you had sensory systems that are operational. But at the same time, we didn’t even understand the environment in which they were processing information.”
In 2017 Vincent, then based at Lancaster University in the United Kingdom, did a world-first experiment to investigate whether foetuses would respond to certain light stimuli. He did this using lasers and ultrasound.
On ultrasound images a third trimester foetus’ eye in the womb appears as a large, round, dark circle. As the eye moves, light reflects off the lens – a bright disc on this dark ball. By tracking this movement, researchers can determine the direction in which a foetus in the womb is looking.
By shining a red laser with three dots against the womb, Vincent and his team were able to show that the foetuses displayed a preference for a “top-heavy” T shape, compared to the inverse.
At the time other researchers in the field challenged these results. But in 2025 a group in Italy saw the same response in their study.
It is an intriguing finding because newborn infants show a strong preference for looking at faces, thought to be one of these rapidly learned abilities post-birth.
However, if the preference for a “face-like” T shape already exists in the womb, this disrupts this idea of how the visual system develops.
Since those early findings, further work by Vincent’s group at the University of Waikato indicates that these third trimester foetuses also show an effect called “anticipation” where they react to a sound cue and look towards a light source before it switches on.
Part of the challenge in the field was that it remained unclear how much light actually gets into the womb, so Vincent set out to address this question by recruiting some mathematical colleagues.
A red moonlit night
Associate Professor Jacob Heerikhuisen’s research involves mathematical modelling of all sorts of different things. But modelling how light particles, called photons, would bounce, scatter and move through clothing and tissue to get into the womb was a new one for him and Dr Zac Isaac, who was doing his PhD research with Jacob at the time.
With Vincent’s help, the team fossicked around in various biology textbooks to find the light properties related to all the different layers – skin, fat, muscle, the wall of the uterus and the amniotic fluid.
Then they built a model to account for all these layers, set realistic parametres for each of them and investigated how much light would get through.
Associate Professor Jacob Heerikhuisen, Dr Zac Isaac and Professor Vincent Reid from the University of Waikato Univeristy of Waikato
“The level of light is comparable to a night sky with a full moon,” Jacob said.
“So certainly when I go outside now, every time there’s a moon, I’m like, oh, yeah, this is like the amount of light that gets through to a foetus. It’s significant.”
Their model also revealed that the wavelength of light more likely to get through was in the red spectrum. Blue and green light did not appear to penetrate far enough.
The work has excited Vincent because of what it means for the environment within the womb that the visual system is already developing in.
According to this modelling the light that is getting through is enough for the foetus to have a visual experience, Vincent said, and he would like to know how that is shaping vision, even before birth.
From a psychology point of view, it was fascinating to think about, but the results have a practical application too, Vincent said, particularly in neonatal care units where pre-term babies are likely experiencing an environment very different to what they should be.
“This work can actually inform what those units should look like, what they should do… which then, in theory, would lead to downstream health benefits for those children.”
Sign up to the Our Changing World monthly newsletter for episode backstories, science analysis and more.
– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
LiveNews: https://nz.mil-osi.com/2026/01/27/our-changing-world-sight-in-the-womb/