Linear development

How wierd is this- I was looking at a review paper [1] of the development of visual acuity in human infants and I plotted the average acuity measurements for the first three years of life. It’s a straight line. A very straight line.

Not only is it testament to the experimental rigour of the studies included in the review but it’s also pretty developmentally odd- I mean what else develops linearly? Height doesn’t. Vocabularly use doesn’t. Number conservation doesn’t.

Does anything else develop linearly? There must be so many non-linear processes involved in the neural development of vision it’s a marvel it comes out linear with respect to age.

[1] Courage, M.L., and Adams, R.J. (1990). Visual acuity assessment from birth to three years using the acuity card procedure: Cross-sectional and longitudinal samples. Ophthalmic and Physiological Optics, 67(9), 713-718.

Acuity was measured with black and white gratings of different spatial frequencies and is shown here in cpd, cycles per degree of visual angle (this is an inverse function of the Snellen rating (eg 20/20).

2 replies on “Linear development”

What about other sensory-related development like auditory acuity or tactile acuity? Are the progresses of those faculties linear as well? The developmental progressions you mentioned (height, vocabulary, number conservation) seems relevant, but not as relevant as sensory progressions.

As far as i know, no one has systemmatically assessed the acuity of the other senses. But i’d still be suprised if their development was linear. It’s not just the three examples i mentioned that aren’t linear- can you think of anything in human development that is strictly linear?

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