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Categorical Perception in Infancy

Categorical perception of colour emerges early in infancy. This has been demonstrated with four-month-olds using habituation \citep{Bornstein:1976of} and visual search \citep{Franklin:2005xk}.
Slightly older infants can make use of colour properties such as red and green to recognise objects. For instance, nine-months-olds can determine whether an object they saw earlier is the same as a subsequently presented object on the basis of its colour \citep{Wilcox:2008jk}.
By the time they are two years old, toddlers who do not comprehend any colour words can use colour categories implicitly in learning and using proper names; for instance, they are able to learn and use proper names for toy dinosaurs that differ only in colour \citep[][Experiment 3]{Soja:1994np}.
So infants and toddlers enjoy categorical perception of colour and may benefit from it in recognising and learning about objects.
However children only acquire concepts of, and words for, colours some time later; and colour concepts, like colour words, are acquired gradually \citep{Pitchford:2005hm,Kowalski:2006hk,Sandhofer:1999if,Sandhofer:2006qo}.
Categorical perception of colour emerges early in infancy, from around four months or earlier, as has been demonstrated using habituation (Bornstein, Kessen and Weiskopf 1976).

‘there was a familiarization phase with one hue repeatedly shown, and then a test phase where the familiar hue was paired with a novel hue across four trials. The time spent looking at the novel hue relative to the test hue during the test phase was calculated (novelty preference)’

Skelton et al, 2017 p. 5549

And most recently, using preferences. Importantly, this experiment involved considering a wide range of potential colour boundaries.
NB: (1) CIELAB space; (2) ‘Euclidean distances in this space do not predict infants’ novelty preference.’

Skelton et al, 2017 figure S4

\citep[Supplementary Material]{skelton:2017_biological} caption: ‘Stimuli plotted in CIELAB perceptual color space (a*,b*). Stimulus pairs for which there was no novelty preference are indicated with black lines joining the stimuli, and pairs where there was a novelty preference are indicated by the absence of these lines. The cross between 7.5R and 5R indicates a pair that was not tested. Euclidean distances in this space do not predict infants’ novelty preference.’
Categorical perception has also been demonstrated at four months of age using pop-out (Franklin, Pilling and Davies 2005).

‘The color of the target was green, and this was kept constant across all trials. The background color was either green (from the same color category, i.e., within-category) or blue (from a different color category, i.e., between-category) to the target’

Franklin et al, 2005 p. 234

This is from the adult version (experiment 1), but was the same in the infant version (experiment 2)
[from caption ] Note that the green-blue boundary is unlike the others in that it coincides with a local minimum of discrimination thresholds.

Before children reliably use colour words correctly, categorical perception explains:

  • habituation -- 4 months

    (Bornstein, Kessen and Weiskopf 1976)

  • pop out [??] -- 4 months

    (Franklin, Pilling and Davies 2005)

  • re-identifying objects -- 9 months

    (Wilcox, Woods and Chapa 2008)

    Slightly older infants can also make use of colour properties such as red and green to recognise objects. For instance, nine-months-olds can determine whether an object they saw earlier is the same as a subsequently presented object on the basis of its colour (Wilcox, Woods and Chapa 2008).
  • learning proper names -- around 2 years
    By the time they are two years old, toddlers who do not comprehend any colour terms can use colour categories implicitly in learning and using proper names; for instance, they are able to learn and use proper names for toy dinosaurs that differ only in colour (Soja 1994: Experiment 3).

    (Soja 1994: Experiment 3)

    So we see categorical perception of colour early in development and it is useful to children.
\subsection{Other cases}
Infants enjoy categorical perception not only of colour but also of orientation \citep{franklin:2010_hemispheric}, speech \citep{Kuhl:1987la,Kuhl:2004nv,Jusczyk:1995it} and facial expressions of emotion \citep{Etcoff:1992zd,Kotsoni:2001ph,Campanella:2002aa}.
Infants enjoy categorical perception not only of colour but also of orientation (Franklin et al. 2010), speech (Kuhl 1987, 2004; Jusczyk 1995) and facial expressions of emotion (Etcoff & Magee 1992; Kotsoni et al. 2001; Campanella et al. 2002).
To recap, infants enjoy categorical perception not only of colour but also of orientation (Franklin et al. 2010), speech (Kuhl 1987, 2004; Jusczyk 1995) and facial expressions of emotion (Etcoff & Magee 1992; Kotsoni et al. 2001; Campanella et al. 2002).

Infants (and adults) enjoy categorical perception of

  • colour (from four months of age or earlier)
  • orientation (five months)
  • facial expressions of emotion (seven months)
  • speech (one month)
  • ...