PAPER Spontaneous non-verbal counting in toddlers Francesco Sella, 1 Ilaria Berteletti, 2 Daniela Lucangeli 3 and Marco Zorzi 1,4,5 1. Department of General Psychology, University of Padova, Italy 2. Department of Psychology, University of Illinois Urbana Champaign, IL, USA 3. Department of Developmental Psychology and Socialization, University of Padova, Italy 4. Center for Cognitive Neuroscience, University of Padova, Italy 5. IRCCS San Camillo Hospital, Venice, Italy Abstract Awealth of studies have investigated numerical abilities in infants and in children aged 3 or above, but research on pre-counting toddlers is sparse. Here we devised a novel version ofan imitation task that was previously used to assess spontaneous focusing on numerosity (i.e. the predisposition to grasp numerical properties of the environment) to assess whether pre-counters would spontaneously deploy sequential (item-by-item) enumeration and whether this ability would rely on the object tracking system (OTS) or on the approximate number system (ANS). Two-and-a-half-year-olds watched the experimenter performingone-by- one insertion of ‘food tokens’ into an opaque animal puppet and then were asked to imitate the puppet-feeding behavior. The number of tokens varied between 1 and 6 and each numerosity was presented many times to obtain a distribution of responses during imitation. Many children demonstrated attention to the numerosity of the food tokens despite the lack of any explicit cueing to the numberdimension. Most notably, the response distributions centered on the target numerosities and showed the classic variability signature that is attributed to the ANS. These results are consistent with previous studies on sequential enumeration in non-human primates and suggest that pre-counting children are capable of sequentially updating the numerosity of non-visible sets through additive operations and hold it in memory for reproducing the observed behavior. Research highlights • We devised a novel version of a puppet-feeding imitation task to assess pre-counters’ spontaneous sequential (item-by-item) enumeration up to 6 items. • Many children showed that they attended to the numerosity of the food tokens despite the lack of any explicit cueing to the number dimension. • The response distributions centered on the target numerosities and showed the classic variability sig- nature that is attributed to the ANS. • Pre-counting children are capable of sequentially updating the numerosity of non-visible sets through additive operations and hold it in memory for reproducing the observed behavior. Introduction Increasing evidence suggests that humans are able, since their first hours of life, to discriminate the numerosity of object sets (Antell & Keating, 1983; Izard, Sann, Spelke & Streri, 2009). Two mechanisms have been highlighted as foundational for the ability to perceive and represent numerical information: the Object Tracking System (OTS) and the Approximate Number System (ANS; Feigenson, Dehaene & Spelke, 2004; Piazza, 2010). The OTS is a domain-general mechanism devoted to tracking a limited number of objects (around 3–4) in space and time. When the OTS is deployed for numerical purposes, it allows fast and exact enumeration of small sets, a phenomenon known as subitizing (Cutini, Scatturin, Basso Moro & Zorzi, 2014; Mandler & Shebo, 1982; Address for correspondence: Francesco Sella or Marco Zorzi, Department of General Psychology, University of Padova, via Venezia 12/2, 35131 Padova, Italy; e-mails: sella.francesco@gmail.com or marco.zorzi@unipd.it © 2015 John Wiley & Sons Ltd Developmental Science 19:2 (2016), pp 329–337 DOI: 10.1111/desc.12299