Dissociation between small and large numerosities in newborn infants

Abstract

In the first year of life, infants possess two cognitive systems encoding numerical information: one for processing the numerosity of sets of 4 or more items, and the second for tracking up to 3 objects in parallel. While a previous study showed the former system to be already present a few hours after birth, it is unknown whether the latter system is functional at this age. Here, we adapt the auditory-visual matching paradigm that previously revealed sensitivity to large numerosities to test sensitivity to numerosities spanning the range from 2 to 12. Across studies, newborns discriminated pairs of large numerosities in a 3:1 ratio, even when the smaller numerosity was 3 (3 vs. 9). In contrast, newborn infants failed to discriminate pairs including the numerosity 2, even at the same ratio (2 vs. 6). These findings mirror the dissociation that has been reported with older infants, albeit with a discontinuity situated between numerosities 2 and 3. Two alternative explanations are compatible with our results: either newborn infants have a separate system for processing small sets, and the capacity of this system is limited to 2 objects; or newborn infants possess only one system to represent numerosities, and this system either is not functional or is extremely imprecise when it is applied to small numerosities.

Representations of space, time, and number in neonates

“…In contrast, infants who experienced opposite changes in numerosity and length from familiarization to test showed no differential looking at the two test displays (M = 32.5 s vs. 35.3 s; F < 1, P > 0.6) even though, in this group, the duration of individual syllables and the line length changed concordantly. This finding suggests that newborns were attending to the overall numerosity of the sequences, as in previous research (8,10 numerical cues, newborn infants spontaneously linked auditory events of longer duration to visual lines of greater length.…”

“…We now know that human newborns, and even inexperienced animals such as newly hatched chicks, are able to discriminate objects on the basis of numerosity a few hours after the start of postnatal experience (8,9). When human newborns are presented with auditory sequences of syllables and visual arrays of objects, they look longer at the arrays that correspond to the auditory sequences in number than at arrays differing in number by a 1:3 ratio (8,10). At birth, humans thus possess representations of approximate numerosity that are abstract enough to enable a generalization across stimuli as varied as sequences of syllables and sets of visual objects.…”

Core mathematical abilities in infants

“…The capacity of this system might not be strictly determined by the number of objects but by the number of "slots" available, which can contain chunks of objects defined by information about color, motion, spatial arrangement, or conceptual category (Feigenson andHalberda, 2004, 2008;Rosenberg and Feigenson, 2013;Wynn et al, 2002;Zosh et al, 2011). There is preliminary evidence that this system might be functional from birth, albeit with a set-size limit of two objects (Coubart et al, 2014).…”

Conceptual correlates of counting: Children’s spontaneous matching and tracking of large sets reflects their knowledge of the cardinal principle

“…Numerical acuity dramatically increases in children between 3 and 5 years-the same period during which children acquire verbal counting Shusterman, Cheung, Taggart et al 3 (Halberda & Feigenson, 2008)-and eventually reaches a discriminability ratio of about 7:8 in Western adults (Barth, Kanwisher, & Spelke, 2003). Developmental change is also evident in the PI system: Newborns can track only two objects (Coubart, Izard, Spelke, Marie, & Streri, 2014); 12-month-olds fail tasks requiring them to track more than three objects simultaneously (Feigenson & Carey, 2003; between the ages of 3 and 6, this limit increases to sets of four or even five (O'Hearn, Hoffman, & Landau, 2011;Ross-Sheehy, Oakes, & Luck, 2003;Starkey & Cooper, 1995).…”