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Occasionally I’m called out for wearing stripes too often, but what can I say, they’re so… visually interesting. And that’s not just me talking here, that’s cold, hard science. As I’ve discovered in my Cognitive Development course with Dr. Bob Siegler, the fact that stripes are more visually interesting makes all the difference when testing infants ability to see.

If you’re still reading, you might want to know why we even care about testing an infant’s vision. Infants’ perceptive systems come to near adult-like levels at a very young age, but developing visual acuity is based on experience with the visual world (visual acuity is vision for fine detail, more or less, and important for distinguishing objects from the rest of the visual field). An example: infants who are born with cataracts that prevent them from seeing can usually have them removed within the first six months of life. When the cataracts are removed and contact lenses are fitted, infants’ visual acuity is no better than a newborn’s, but acuity can improve rapidly even within the first hour, and the improvements continue over the following month¹. There is a cutoff time though: if infants aren’t able to see for the first three years of life, performing surgery after that time to restore vision won’t be helpful, as the visual system won’t be able properly develop. Thus, it is important that we know an infant’s visual ability, so parents can make informed choices about surgical procedures or vision correction.

The problem with testing infants’ vision is that you can’t just point them towards a Snellen chart and ask them to read the letters. Instead, judging infants’ vision is based on the preferential looking paradigm; when two objects are displayed side by side, the researcher records whether or not infants are consistently looking at one of them more. If so, they must be able to perceive the difference between the two objects. To test an infant’s visual abilities, they are presented with a field of grey, and a field of alternating black and white stripes. Depending on the spatial frequency of the stripes, infants either perceive the stripes themselves, or just another field of grey. If infants are able to make out the stripes, they will spend more time looking at the striped half of the visual field, because the stripes are more visually interesting and infants would rather look at stripes than a grey field. This lets researchers know if infants can see, and based on spatial frequency of the stripes, and the distance from the stripes, we can determine the level of vision the infants are at.

So, it’s important that researchers can test infant vision, because experiencing the visual world at a young age is key to a properly developing visual system. Plus, when I go out wearing stripes, I know that babies will probably want to look at me.

1. Siegler, R. S. & Alibali, M. W. (2004). Children’s thinking, 4th edition. Upper Saddle River, NJ: Prentice Hall. [↩]