The SNARC effect: a preregistered study on the interaction of horizontal, vertical, and sagittal spatial-numerical associations

Spatial associations of number and pitch in human newborns

Humans use space to think, reason about, externally represent, and even talk about many dimensions (e.g., time, pitch height). One dimension that appears to exploit spatial resources is the mental representation of the numerosity of a set in the form of a mental number line. Although the horizontal number-space mapping is present from birth (small-left vs. large-right), it is unknown whether it extends to other spatial axes from birth or whether it is later acquired through development/experience. Moreover, newborns map changes in pitch height onto a vertical axis (low pitch-bottom vs. high pitch-top), but it is an open question whether it extends to other spatial axes. We presented newborns (N = 64 total, n = 16 per experiment, 0-4 days) with an auditory increase/decrease in magnitude along with a visual figure on a vertically oriented screen (bottom vs. top, change in number: Experiments 1 and 2; change in pitch: Experiment 3) or on a horizontally oriented screen (left vs. right, change in pitch: Experiment 4). Newborns associated changes in magnitude with a vertical axis only when experiencing an increase in magnitude (increase/up); however, the possibility that visuospatial biases could account for this asymmetric pattern are discussed. Newborns did not map changes in pitch horizontally (Experiment 4), in line with previous work showing that the horizontal mapping of number at birth does not generalize to other dimensions. These findings suggest that the flexible use of different spatial axes to map magnitude is not functional at birth and that the horizontal mapping of number might be privileged.

Spatial coding of arithmetic operations in early learning: an eye tracking study in first-grade elementary school children

A growing body of evidence indicates that mental calculation in adults is accompanied by horizontal attention shifts along a mental continuum representing the range of plausible answers. The fast deployment of spatial attention suggests a predictive role in guiding the search for the answer. The link between arithmetic and spatial functions is theoretically justified by the need to alleviate the cognitive load of mental calculation, but the question of how this link establishes during development gives rise to opposing views emphasizing either biological or cultural factors. The role of education, in particular, remains debated in the absence of data covering the period when children learn arithmetic. In this study, we measured gaze movements, as a proxy for attentional shifts, while first-grade elementary school children solved single-digit additions and subtractions. The investigation was scheduled only a few weeks after the formal teaching of symbolic subtraction to assess the role of spatial attention in early learning. Gaze patterns revealed horizontal- but not vertical- attentional shifts, with addition shifting the gaze more rightward than subtraction. The shift was observed as soon as the first operand and the operator were presented, corroborating the view that attention is used to predictively identify the portion of the numerical continuum where the answer is likely to be located, as adult studies suggested. The finding of a similar gaze pattern in adults and six-year-old children who have just learned how to subtract single digits challenges the idea that arithmetic problem solving requires intensive practice to be linked to spatial attention.

Effect of spatial training on space-number mapping: a situated cognition account

From an embodied perspective of cognition, number processing influences the spatial organization of motor responses showing faster left/right responses to small/large numbers. Recent evidence suggests that such spatial-numerical associations (SNAs) along the transverse and sagittal planes are mutually exclusive with respect to the spatial reference frames used by the participant. Specifically, in egocentric and allocentric frames, SNAs appear along the sagittal and transverse plane, respectively. The first aim of this study was to replicate previous findings. The second aim was to explore the role of switching spatial reference frames in SNAs occurrence according to the processed plane. Consequently, during a referential frame switching (RFS) training, participants were required to identify targets based on an embodied avatar's perspective. Using a random number generation (RNG) task after observing an avatar's displacement, we investigated the effect of RFS training on SNAs organization across the different planes (Experiment 1 & 2 for the egocentric and allocentric perspectives, respectively). Both experiments replicated previous results, but more importantly, RFS training enables the development of new situated cognition strategies from egocentric perspectives and the generalization of transverse SNAs to other planes from allocentric perspectives.

Dichotomous horizontal representation of acute deterioration risk on illnesses

The possibility that risks interact with spatial information (such as the SNARC effect) has been explored but studies did not demonstrate a consistent left-to-right representation of risks. This is probably due to the perception of risk being different in each individual experience. The present study aimed to clarify the spatial characteristics of acute deterioration risks perceived from illnesses. Registered nurses and general students participated in the present experiment. They were instructed to judge, by pressing one of the left/right response buttons, whether the risk of a given target (illness name) presented on a computer screen was higher or lower compared to that of a standard stimulus. Reaction times to the target were measured. No spatial-risk association was observed in the comprehensive analysis, but further inspection revealed that approximately half of the participants have a left-to-right representation and the other half have a right-to-left representation. Moreover, participants' responses appeared to be faster when the target was representationally farther away from the standard stimulus (i.e., distance effect). These findings therefore suggest a spatially aligned magnitude representation of acute deterioration risk (i.e., mental risk line) but this horizontal risk orientation is likely to be dichotomous depending on the individuals and/or given situations.

Practice-induced SNARC: evidence from a null-SNARC sample

The mental representation of numbers inherently involves a spatial organization, often positioning smaller numbers to the left and larger numbers to the right. The SNARC effect, characterized by faster responses to small numbers using the left hand and vice versa for large numbers, is typically attributed to this left-to-right oriented mental number line (MNL). However, the direction of the SNARC effect seems to rely on reading direction, with most research exploring these mechanisms conducted within left-to-right reading cultures where the SNARC effect is prevalent. This study takes advantage of a sample from a left-to-right reading culture that does not exhibit the SNARC effect, allowing us to isolate and elucidate the stand-alone effects of recent experiences on SNARC. Therefore, the current study aims to investigate how MNL-compatible and MNL-incompatible practices induce an effect within a sample lacking the SNARC effect. To accomplish this, we reinvited the individuals from the sample which had previously shown no SNARC, and retested those who agreed to take part in the current study after an MNL-compatible or MNL-incompatible practice manipulation. The findings revealed an absence of the SNARC effect with MNL-compatible practices. Conversely, MNL-incompatible practices yielded a reverse SNARC effect. These results prompt a discussion on SNARC mechanisms within the framework of practice effects.

Simultaneous but independent spatial associations for pitch and loudness

For the auditory dimensions loudness and pitch a vertical SARC effect (Spatial Association of Response Codes) exists: When responding to loud (high) tones, participants are faster with top-sided responses compared to bottom-sided responses and vice versa for soft (low) tones. These effects are typically explained by two different spatial representations for both dimensions with pitch being represented on a helix structure and loudness being represented as spatially associated magnitude. Prior studies show incoherent results with regard to the question whether two SARC effects can occur at the same time as well as whether SARC effects interact with each other. Therefore, this study aimed to investigate the interrelation between the SARC effect for pitch and the SARC effect for loudness in a timbre discrimination task. Participants (N = 36) heard one tone per trial and had to decide whether the presented tone was a violin tone or an organ tone by pressing a top-sided or bottom-sided response key. Loudness and pitch were varied orthogonally. We tested the occurrence of SARC effects for pitch and loudness as well as their potential interaction by conducting a multiple linear regression with difference of reaction time (dRT) as dependent variable, and loudness and pitch as predictors. Frequentist and Bayesian analyses revealed that the regression coefficients of pitch and loudness were smaller than zero indicating the simultaneous occurrence of a SARC effects for both dimensions. In contrast, the interaction coefficient was not different from zero indicating an additive effect of both predictors.

Distinct neural mechanisms for action access and execution in the human brain: insights from an fMRI study

Goal-directed actions are fundamental to human behavior, whereby inner goals are achieved through mapping action representations to motor outputs. The left premotor cortex (BA6) and the posterior portion of Broca's area (BA44) are two modulatory poles of the action system. However, how these regions support the representation-output mapping within the system is not yet understood. To address this, we conducted a finger-tapping functional magnetic resonance imaging experiment using action categories ranging from specific to general. Our study found distinct neural behaviors in BA44 and BA6 during action category processing and motor execution. During access of action categories, activity in a posterior portion of BA44 (pBA44) decreased linearly as action categories became less specific. Conversely, during motor execution, activity in BA6 increased linearly with less specific categories. These findings highlight the differential roles of pBA44 and BA6 in action processing. We suggest that pBA44 facilitates access to action categories by utilizing motor information from the behavioral context while the premotor cortex integrates motor information to execute the selected action. This finding enhances our understanding of the interplay between prefrontal cortical regions and premotor cortex in mapping action representation to motor execution and, more in general, of the cortical mechanisms underlying human behavior.

The spatial representation of loudness in a timbre discrimination task

When participants decide whether a presented tone is loud or soft they react faster to loud tones with a top-sided response key in comparison to a bottom-sided response key and vice versa for soft tones. This effect is comparable to the well-established horizontal Spatial-Numerical Association of Response Codes (SNARC) effect and is often referred to as Spatial-Musical Association of Response Codes (SMARC) effect for loudness. The SMARC effect for loudness is typically explained by the assumption of a spatial representation or by the polarity correspondence principle. Crucially, both theories differ in the prediction of the SMARC effect when loudness is task-irrelevant. Therefore, we investigated whether the SMARC effect still occurs in a timbre discrimination task: Participants (N = 36) heard a single tone and classified its timbre with vertically arranged response keys. Additionally, the tone's loudness level varied in six levels. In case of a spatial representation, the SMARC effect should still occur while in case of polarity corresponding principle, the effect should be absent. Results showed that the SMARC effect was still present and that the differences between top-sided and bottom-sided responses were a linear function of loudness level indicating a continuous spatial representation of loudness.

Multimodality matters in numerical communication

Modern society depends on numerical information, which must be communicated accurately and effectively. Numerical communication is accomplished in different modalities-speech, writing, sign, gesture, graphs, and in naturally occurring settings it almost always involves more than one modality at once. Yet the modalities of numerical communication are often studied in isolation. Here we argue that, to understand and improve numerical communication, we must take seriously this multimodality. We first discuss each modality on its own terms, identifying their commonalities and differences. We then argue that numerical communication is shaped critically by interactions among modalities. We boil down these interactions to four types: one modality can amplify the message of another; it can direct attention to content from another modality (e.g., using a gesture to guide attention to a relevant aspect of a graph); it can explain another modality (e.g., verbally explaining the meaning of an axis in a graph); and it can reinterpret a modality (e.g., framing an upwards-oriented trend as a bad outcome). We conclude by discussing how a focus on multimodality raises entirely new research questions about numerical communication.