Imagine a baby’s nursery, and two colour palettes usually come to mind; bold high contrast black and white patterns, or soothing pastel rainbows. The difference is pretty striking, and one option under-estimates infant vision, while the other over-estimates it. Today we’re talking about how colourful the world looks to babies, but first we need to understand how we work out what they can see.
How do we know what colours a baby can see?
The saying ‘never work with animals or children’ can imply to scientists that these groups are so unpredictable that working with them results in random data, particularly for those participants who aren’t able to press buttons, or verbally report what they’re seeing. However, developmental science has shown that infant behavior is actually, on average, very predictable. If you trust an undergraduate to spend 3 hours in a dark room doing a long repetative task, you can certainly trust a baby to look at some colours.
In the 50s, Fantz and collegues were among the first to demonstrate this reliability in behaviour by pairing simple objects or pictures (‘stimuli’) together, and recording what infants looked for longer at. Pairing a face and a scrambled face together results in infants on average looking longer at the face than its’ scrambled partner (see figure 1 right – example 12 for what these look like). This idea is known as ‘preferential looking’, and is still used by developmental psychologists today, and these findings have proven to be highly replicable and reliable.
Figure 1. Left : an early example of a Fantz looking box. Infants lie on their backs on a sliding bed while researchers look the top to record the infant looks to the left or the right of centre. Right : an example of some of the pairs used in Fantz box.
One of the most memorable findings is that infants would rather look at a high contrast stimulus than a low contrast one (see figure 1 right, example 9 for a pairing of different contrast levels). This is likely the origin of the pervasive ‘babies only see in black and white’ myth commonly encountered by developmental researchers working in colour science. However, research by scientists such as Davida Teller in the 1980s harnessed the power of preferential looking to carry out psychophysical** experiments on infant colour vision, showing that infants do see colour. Stimuli were paired to show infants will look preferentially at chromatic over achromatic stimuli, that looking increases with increasing saturation, demonstrating that it is possible to measure colour discrimination thresholds of even very young infants.
The methods used to study the development of colour perception have hugely expanded since then, and in addition to preferential looking measures researchers use methods such as fNIRs (a measure of blood flow to the brain in response to stimuli, particularly suited to a set of participants without much hair!), EEG (measure of electrical activity taken from the scalp), and eye movement data (such as target detection, looking duration, or gaze patterns) to reliably build up a picture of infant vision and colour perception.
**note ‘psychophysical’ is a fancy way of saying ‘having total control over your stimulus, and then measuring how it appears to your participant. For example, I could put the T.V. on, and turn it up by 1 point, and get you to rate on a 1-10 scale how loud it seems. If you’re anything like me, at some point you can’t hear it, and at some point it’s just loud and turning it up more doesn’t make much difference to how loud it seems. This is essentially a psychophysical experiment, I’m controlling the input (T.V. volume), and you’re reporting how loud it actually feels.
How do babies see colour?
The infant retina (the part of the eye with light sensitive cells) has the same colour receptors found on adult retinas. Comparing the retina of an adult and an infant side-by-side, infant’s colour receptors are noticeably shorter and not as densely packed as they are in adults. Over the first 15-months these cells elongate and migrate towards the fovea (which in adults is particularly densely packed with colour receptors).
Of course, having the same tools for colour vision doesn’t guarantee that infant and adult colour vision will be working in the same way. By pairing different colours, researchers have shown that even newborns are able to discriminate intense red light from equally intense white, but not a saturated blue from its achromatic (meaning, not coloured) partner. The ability to tell apart blue comes ‘online’ later, at around 2-3 months of age, and we can be confident that by 3 months old infants, like adults, have two paths for colour vision (a ‘red-green’ & ‘blue-yellow’ pathway – see figure 2), and a luminance pathway (light vs dark).
Figure 2. Showing how the two chromatic pathways of colour vision combine for us to see in colour. You can see that the calling these the ‘red green’ and ‘blue yellow’ are a bit of a misnomer, but these pathways show how the signals from colour receptors in our eye combine to tell us how much ‘red vs green’ or ‘blue vs yellow’ is present.
Although infants have the same toolkit and pathways to seeing colour there are differences between what adults and infants see. The difference between two colours needs to be much larger for infants to be able to see it. Two shades of red that are only slightly different may look identical to infants. How big a difference is needed for a child to tell apart different shades of colour decreases exponentially over development– Knoblauch et al show that with every doubling of age (e.g. from 3 to 6 months, or 6 to 12 months) the size of the difference needed halves. This explains why those aesthetic pastel colours in nurseries may be wasted on babies – the saturation of these colours may be below what infants can reliably discriminate from grey.
We understand a great deal about how maturing physiology shapes how babies colour their world, but there is still much research to be done about what infants do with this colour vision. How does a looking preference in infancy turn into what we call aesthetic preference (or ‘liking’) in adults? When do infants learn what colour objects and environments are supposed to be? What happens if infants get a different visual input when they're young? Studying infants can show what information we learn to tune into in order to process our world efficiently and effectively, and reveals how the ‘default settings’ of the visual system lay the foundations of our adult experience with colour.
Can babies be colourblind?
Colourblindness is more accurately described as 'colour vision deficiency' (CVD) as it's just like the colour pallette being used to colour the world is different, rather than there being no colour at all. Total colourblindness is very rare, but the most common type of CVD ('red-green colourblindness') occurs in about 1 in 12 people who are XY (boys), and rates are much lower in people who are XX (girls), only 1 in 200. As this sort of CVD is genetic, then yes, babies would be born with it.
At the moment, there's no 'in lab' test that can really be done with babies to find out if they have CVD. Instead we have to wait until the children are school age and they can tell us what they see when we give them a CVD test. These tests are specially designed so that people who have CVD give different responses to people who do not have CVD. In the UK mandatory screening for CVD is no longer part of the health screening that primary school children get, although it did used to be. This is a pretty controversial decision as it means that some children may not ever know they have CVD, or may find out at the point of taking a test for their chosen career (e.g. pilot). Given how colour coded the school environment is, it's possible that some children may find school difficult, or feel excluded without knowing why. For example, they might be unable to complete a maths puzzle because it relies on telling apart red and green blocks, or parts of their textbook might not be accessible to them. These small challenges might add up, but currently there is very little information about the impact of undiagnosed and diagnosed CVD on wellbeing in schools.
Find out more:
Some quick facts about the development of vision https://www.youtube.com/watch?v=4dLpqs4n-B8
Brown, A. M., & Lindsey, D. T. (2013). Infant color vision and color preferences: a tribute to Davida Teller. Visual Neuroscience, 30(5-6), 243-250. https://doi.org/10.1017/S0952523813000114
Knoblauch, K., Vital-Durand, F., & Barbur, J. L. (2001). Variation of chromatic sensitivity across the life span. Vision research, 41(1), 23-36. https://doi.org/10.1016/S0042-6989(00)00205-4
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