What the numbers mean

All three cone types are present at birth. What is limited early on is sensitivity, not the hardware: a newborn needs a much bigger colour difference before it registers as a difference at all. Red–green and blue–yellow discrimination both reach adult-like reliability around three months.

Did you know?

Blue–yellow discrimination is demonstrable at one to two months. So the first colour distinction a baby makes is often not the one the toy aisle is built around.

Why this works at this age

What catches their eye now

Ranked by what this age is actually good at: bold, close and moving. Nothing here is a milestone and nothing here is a test.

01

Your face, close up

A face at about 30 cm is coarse, high-contrast and moving — the three things this age is best at, all at once.

Costs nothing.
02

Black-and-white cards

Bold shapes at the coarsest scale, at nearly full contrast. At this age that is almost the only kind of pattern that clears the threshold.

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Sources

  • Banks, M.S. & Salapatek, P. (1978). "Acuity and contrast sensitivity in 1-, 2-, and 3-month-old human infants." Investigative Ophthalmology & Visual Science 17(4), 361–365.
    Acuity estimated a different way, from where full contrast sensitivity functions cut off, and the very low spatial frequency of peak contrast sensitivity in early infancy.
  • Banks, M.S. (1980). "The development of visual accommodation during early infancy." Child Development 51(3), 646–666.
    That steady-state focus error and accommodative response slope improve up to about 3–4 months, and that accommodative error does not meaningfully limit infant acuity.
  • Braddick, O., Atkinson, J., French, J. & Howland, H.C. (1979). "A photorefractive study of infant accommodation." Vision Research 19(12), 1319–1330.
    Consistent focusing behaviour at a low accommodative demand of about 1.3 D (≈ 75 cm) emerging between 3 and 6 months.
  • Clavadetscher, J.E., Brown, A.M., Ankrum, C. & Teller, D.Y. (1988). "Spectral sensitivity and chromatic discriminations in 3- and 7-week-old human infants." Journal of the Optical Society of America A 5(12), 2093–2105.
    That few 3-week-olds show reliable chromatic discrimination while most 7-week-olds do, and the long-wavelength advantage at 3 weeks.
  • Haynes, H., White, B.L. & Held, R. (1965). "Visual accommodation in human infants." Science 148(3669), 528–530.
    The median 19 cm focus distance in alert newborns — the origin of the "babies see 8–12 inches" claim, cited so the app can state what the paper does and does not support.
  • Held, R., Birch, E.E. & Gwiazda, J. (1980). "Stereoacuity of human infants." Proceedings of the National Academy of Sciences 77(9), 5572–5574.
    The abrupt onset of stereopsis between about 3 and 5 months — explained in the app and never drawn, because a flat screen cannot present it.
  • Mohn, G. & van Hof-van Duin, J. (1986). "Development of the binocular and monocular visual fields of human infants during the first year of life." Clinical Vision Sciences 1(1), 51–64.
    The restricted newborn visual field and its expansion over the first year — described in the app, deliberately not rendered as a vignette.
  • Neijzen, C.M., de Wit, F.M., et al. (2025). "Reference values for the Teller Acuity Cards II (TAC II) in infants and preverbal children, a meta-analysis." Acta Ophthalmologica. doi:10.1111/aos.17447.
    The behavioural binocular grating-acuity curve the app renders, and its stated uncertainty of approximately 0.16 log10 units, flat with age.
  • Norcia, A.M. & Tyler, C.W. (1985). "Spatial frequency sweep VEP: visual acuity during the first year of life." Vision Research 25(10), 1399–1408.
    The swept-VEP acuity curve reported alongside the behavioural one as an upper bound, and the 24.3 c/deg adult reference measured in the same apparatus.
  • Norcia, A.M., Tyler, C.W. & Hamer, R.D. (1990). "Development of contrast sensitivity in the human infant." Vision Research 30(10), 1475–1486.
    Contrast threshold at low spatial frequency falling from 7 % at 2–3 weeks to a 0.5 % asymptote by 9 weeks, against an adult 0.32–0.22 %, and the two-phase shape of contrast development.
  • Peeples, D.R. & Teller, D.Y. (1975). "Color vision and brightness discrimination in two-month-old human infants." Science 189(4208), 1102–1103.
    Established red/white chromatic discrimination at two months of age.
  • Regal, D.M. (1981). "Development of critical flicker frequency in human infants." Vision Research 21(4), 549–555.
    Low critical flicker fusion frequency in the first weeks reaching near-adult values within months — described, not rendered.
  • Skelton, A.E., Maule, J. & Franklin, A. (2022). "Infant colour perception: Insight into perceptual development." Child Development Perspectives 16(2), 90–95.
    The review timeline placing the emergence of colour vision between about 3 weeks and 3 months.
  • Varner, D., Cook, J.E., Schneck, M.E., McDonald, M. & Teller, D.Y. (1985). "Tritan discriminations by 1- and 2-month-old human infants." Vision Research 25(6), 821–831.
    Demonstrable tritan (S-cone) discrimination at 1 and 2 months, which is why the app does not dramatise a months-long absence of blue-yellow vision.
  • ISO 226:2003, Acoustics — Normal equal-loudness-level contours; with Fastl, H. & Zwicker, E. (2007). Psychoacoustics: Facts and Models, 3rd ed. Springer (minimum audible field).
    The adult minimum-audible-field reference curve that the infant elevation is added to.
  • Olsho, L.W., Koch, E.G., Carter, E.A., Halpin, C.F. & Spetner, N.B. (1988). "Pure-tone sensitivity of human infants." Journal of the Acoustical Society of America 84(4), 1316–1324.
    The primary pure-tone threshold dataset underlying the infant audiogram.
  • Werner, L.A. (2002). "Infant auditory capabilities." Current Opinion in Otolaryngology & Head and Neck Surgery 10(5), 398–402.
    Behavioural thresholds of 40–55 dB SPL at 1 month falling to 10–30 dB SPL by 6–12 months; a 4 kHz threshold only ~10 dB above adult at 6 months while low frequencies mature into childhood; and that cochlear function is mature at term, so the elevation is middle-ear and central.

This is not a vision or hearing test. If anything worries you, speak to your paediatrician or a paediatric eye doctor.

This is a perceptual approximation, not a reconstruction of what your baby sees. Real babies vary a great deal from one another.

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