Maria Dolores de Hevia

Numerical and spatial processing are closely intertwined, yet whether spatial–numerical associations generalize across distinct quantitative systems remains an open question. We investigated how stimulus position (central, left, and right visual fields) modulates performance across three systems: the Approximate Number System (ANS), the Object Tracking System (OTS), and Visual Working Memory (VWM). Using a go/no-go paradigm that avoided explicit lateralized responses, adult participants performed numerosity discrimination or change-detection tasks while stimuli were presented at varying spatial locations. Performance across all tasks was primarily shaped by core computational demands—numerical ratio in the ANS and set size in OTS and VWM. Critically, only the ANS showed a spatial–numerical congruency effect (i.e., Spatial-Numerical Association of Response Codes (SNARC) effect), with faster responses when smaller numerosities appeared on the left and larger ones on the right. OTS instead exhibited a strong central advantage, with higher accuracy and faster responses for centrally presented stimuli, but no magnitude-dependent spatial organization. VWM showed minimal spatial modulation, with performance driven almost entirely by memory load. We examined whether individual differences in OTS and VWM performance were correlated: spatial-bias indices based on accuracy were not correlated across tasks, but Reaction Time–based and efficiency-based measures, as well as center-position performance, showed reliable positive associations, in line with previous literature. These findings indicate that spatial–numerical congruency is specific to approximate magnitude processing and does not generalize to systems relying on discrete, item-based representations. This pattern suggests that the continuous and compressed representational format of the ANS may be a key condition for the emergence of spatial–numerical associations.

In adults, a reciprocal interaction exists between the processing of manual actions and different dimensions of magnitudes (number, size, time), as evidenced by cognitive and neurofunctional studies. Given that the ability to conceptualise numerical information in relation to spatial magnitude is functional at birth, we may hypothesise that the interrelation between the action perception system and the perception of magnitude develops throughout key stages of the early sensori-motor development. We present here a scoping review on how this interaction has been documented in early development. By systematically collecting articles reporting measures of both manual action (perception or production) and magnitude processing, we identified 21 studies conducted in human infants younger than three years of age. The majority of studies aimed at assessing infants' propensity to adapt their reaching or grasping actions to the size of objects (n = 15); others addressed the ability of infants to understand and predict other’s object-directed actions based on size information (n = 4). Finally, the most recent studies focused on infants’ ability to preferentially associate different hand apertures with congruent numerosities (n = 2), using habituation paradigms. The vast majority of these features were studied at the ages of 6 and 9 months. We present a state-of-the-art on the early development of the magnitude-action link, and suggest future research directions to help elucidate the ontogeny of the interaction between these two fundamental cognitive abilities.

Models of numerical cognition consider a visuo-spatial representation to be at the core of numerical processing, the ‘mental number line’. Two main interference effects between number and space have been described: the SNARC effect reflects a small number/left side and large number/right side association (number-location mapping); the size-congruity effect (SCE) reflects a small number/small size and large number/large size association (number-size mapping). Critically, a thorough investigation on the representational source for these two number-space mappings is lacking, leaving open the question of whether the same representation underlies both phenomena. Here, we build on a recent study (Viarouge and de Hevia in Front Hum Neurosci 15:750964, 2021) in order to address this question in three experiments, by systematically manipulating the presence of the two conditions that might elicit an interaction between SNARC and SCE: (i) an implicit task whereby numerical and spatial information are task-irrelevant, (ii) a design in which the number-space congruency relative to both mappings vary at the same level -either both within or between blocks. Experiment 1 replicated the interaction between the two mappings when both factors were present. Experiments 2 and 3 dissociated the two factors by varying the two mappings at the same level but using an explicit comparison task (Experiment 2), or by using an implicit task but with mappings varying at different levels (Experiment 3). We found that both factors, either in combination or used in isolation, drive the interaction between the two number-space mappings. These findings are discussed in terms of the weight given to each mapping, suggesting that a single representation encompassing both number-space mappings is therefore activated whenever both mappings are given equal weight through task requirements.

For a long time, newborns were considered as human beings devoid of perceptual abilities who had to learn with effort everything about their physical and s

In the last decades, a growing body of literature has focused on the link between number and action. Many studies conducted on adult participants have provided evidence for a bidirectional influence between numerosity processing and grasping or reaching actions. However, it is not yet clear whether this link is functional in early infancy. Here, we used the event-related potential (ERP) technique to record electrical activity of the brain in response to number–hand pairings. We implemented a cueing paradigm where 3- to 4-month-old infants observed images showing either congruency (e.g., a large numerosity primed by a large hand opening) or incongruency (e.g., a large numerosity primed by a small hand opening). Infants’ brain activity was modulated by the congruency of the pairings: amplitudes recorded over frontal and parietal-occipital scalp positions differed for congruent versus incongruent pairings. These findings suggest that the association between number and hand action processing is already functional early in life.

From the very first days of life, newborns are not tied to represent narrow, modality- and object-specific aspects of their environment. Rather, they sometimes react to abstract properties shared by stimuli of very different nature, such as approximate numerosity or magnitude. As of now, however, there is no evidence that newborns possess abstract representations that apply to small sets: in particular, while newborns can match large approximate numerosities across senses, this ability does not extend to small numerosities. In two experiments, we presented newborn infants (N = 64, age 17 to 98 hours) with patterned sets AB or ABB simultaneously in the auditory and visual modalities. Auditory patterns were presented as periodic sequences of sounds (AB: triangle-drum-triangle-drum-triangle-drum …; ABB: triangle-drum-drum-triangle-drum-drum-triangle-drum-drum …), and visual patterns as arrays of 2 or 3 shapes (AB: circle-diamond; ABB: circle-diamond-diamond). In both experiments, we found that participants reacted and looked longer when the patterns matched across the auditory and visual modalities – provided that the first stimulus they received was congruent. These findings uncover the existence of yet another type of abstract representations at birth, applying to small sets. As such, they bolster the hypothesis that newborns are endowed with the capacity to represent their environment in broad strokes, in terms of its most abstract properties. This capacity for abstraction could later serve as a scaffold for infants to learn about the particular entities surrounding them.