Matthias Hartmann

Moving along the Mental Number Line: Interactions between Whole-Body Motion and Numerical Cognition.

Active head turns to the left and right have recently been shown to influence numerical cognition by shifting attention along the mental number line. In the present study, we found that passive whole-body motion influences numerical cognition. In a random-number generation task (Experiment 1), leftward and downward displacement of participants facilitated small number generation, whereas rightward and upward displacement facilitated the generation of large numbers. Influences of leftward and rightward motion were also found for the processing of auditorily presented numbers in a magnitude-judgment task (Experiment 2). Additionally, we investigated the reverse effect of the number-space association (Experiment 3). Participants were displaced leftward or rightward and asked to detect motion direction as fast as possible while small or large numbers were auditorily presented. When motion detection was difficult, leftward motion was detected faster when hearing small number and rightward motion when hearing large number. We provide new evidence that bottom-up vestibular activation is sufficient to interact with the higher-order spatial representation underlying numerical cognition. The results show that action planning or motor activity is not necessary to influence spatial attention. Moreover, our results suggest that self-motion perception and numerical cognition can mutually influence each other.

Spatial Biases During Mental Arithmetic: Evidence from Eye Movements on a Blank Screen

While the influence of spatial-numerical associations in number categorization tasks has been well established, their role in mental arithmetic is less clear. It has been hypothesized that mental addition leads to rightward and upward shifts of spatial attention (along the “mental number line”), whereas subtraction leads to leftward and downward shifts. We addressed this hypothesis by analyzing spontaneous eye movements during mental arithmetic. Participants solved verbally presented arithmetic problems (e.g., 2 + 7, 8–3) aloud while looking at a blank screen. We found that eye movements reflected spatial biases in the ongoing mental operation: Gaze position shifted more upward when participants solved addition compared to subtraction problems, and the horizontal gaze position was partly determined by the magnitude of the operands. Interestingly, the difference between addition and subtraction trials was driven by the operator (plus vs. minus) but was not influenced by the computational process. Thus, our results do not support the idea of a mental movement toward the solution during arithmetic but indicate a semantic association between operation and space.

Spatial cognition, body representation and affective processes: the role of vestibular information beyond ocular reflexes and control of posture

A growing number of studies in humans demonstrate the involvement of vestibular information in tasks that are seemingly remote from well-known functions such as space constancy or postural control. In this review article we point out three emerging streams of research highlighting the importance of vestibular input: (1) Spatial Cognition: Modulation of vestibular signals can induce specific changes in spatial cognitive tasks like mental imagery and the processing of numbers. This has been shown in studies manipulating body orientation (changing the input from the otoliths), body rotation (changing the input from the semicircular canals), in clinical findings with vestibular patients, and in studies carried out in microgravity. There is also an effect in the reverse direction; top-down processes can affect perception of vestibular stimuli. (2) Body Representation: Numerous studies demonstrate that vestibular stimulation changes the representation of body parts, and sensitivity to tactile input or pain. Thus, the vestibular system plays an integral role in multisensory coordination of body representation. (3) Affective Processes and Disorders: Studies in psychiatric patients and patients with a vestibular disorder report a high comorbidity of vestibular dysfunctions and psychiatric symptoms. Recent studies investigated the beneficial effect of vestibular stimulation on psychiatric disorders, and how vestibular input can change mood and affect. These three emerging streams of research in vestibular science are—at least in part—associated with different neuronal core mechanisms. Spatial transformations draw on parietal areas, body representation is associated with somatosensory areas, and affective processes involve insular and cingulate cortices, all of which receive vestibular input. Even though a wide range of different vestibular cortical projection areas has been ascertained, their functionality still is scarcely understood.

Pushing forward in embodied cognition: may we mouse the mathematical mind?

Freely available software has popularized “mousetracking” to study cognitive processing; this involves the on-line recording of cursor positions while participants move a computer mouse to indicate their choice. Movement trajectories of the cursor can then be reconstructed off-line to assess the efficiency of responding in time and across space. Here we focus on the process of selecting among alternative numerical responses. Several studies have recently measured the mathematical mind with cursor movements while people decided about number magnitude or parity, computed sums or differences, or simply located numbers on a number line. After some general methodological considerations about mouse tracking we discuss several conceptual concerns that become particularly evident when “mousing” the mathematical mind.

Numbers in the eye of the beholder: What do eye movements reveal about numerical cognition?

The eyes, often called the window to our minds, reveal the focus of spatial attention and are therefore a powerful research tool for the study of spatial processing and spatially related higher cognitive functions. The aim of this paper is to highlight the potential of eye movement analysis in the domain of numerical cognition, to review several relevant findings, and to provide an outlook for future research.

Self-motion perception influences number processing: evidence from a parity task.

We investigated the role of horizontal body motion on the processing of numbers. We hypothesized that leftward self-motion leads to shifts in spatial attention and therefore facilitates the processing of small numbers, and vice versa, we expected that rightward self-motion facilitates the processing of large numbers. Participants were displaced by means of a motion platform during a parity judgment task. We found a systematic influence of self-motion direction on number processing, suggesting that the processing of numbers is intertwined with the processing of self-motion perception. The results differed from known spatial numerical compatibility effects in that self-motion exerted a differential influence on inner and outer numbers of the given interval. The results highlight the involvement of sensory body motion information in higher-order spatial cognition.

Pupillometry: The Eyes Shed Fresh Light on the Mind

Recent studies provide promising methodological advances in the use of pupillometry as on-line measurement of cognitive processes and show that visual attention allocation, mind-wandering, mental imagery, and even rhyme expectations can influence the size of the human pupil.

Loudness counts: Interactions between loudness, number magnitude, and space

ATOM (a theory of magnitude) suggests that magnitude information of different formats (numbers, space, and time) is processed within a generalized magnitude network. In this study we investigated whether loudness, as a possible indicator of intensity and magnitude, interacts with the processing of numbers. Small and large numbers, spoken in a quiet and a loud voice, were simultaneously presented to the left and right ear (Experiments 1a and 1b). Participants judged whether the number presented to the left or right ear was louder or larger. Responses were faster when the smaller number was spoken in a quiet voice, and the larger number in a loud voice. Thus, task-irrelevant numerical information influenced the processing of loudness and vice versa. This bi-directional link was also confirmed by classical SNARC paradigms (spatial–numerical association of response codes; Experiments 2a–2c) when participants again judged the magnitude or loudness of separately presented stimuli. In contrast, no loudness–number association was found in a parity judgment task. Regular SNARC effects were found in the magnitude and parity judgment task, but not in the loudness judgment task. Instead, in the latter task, response side was associated with loudness. Possible explanations for these results are discussed.

Exploring the numerical mind by eye-tracking: a special issue.

Psychological research has a long track record of developing tools for our understanding of mental processes. Prominent among these tools are the measurement of the duration of cognitive processes (mental chronometry) and the localization of these processes in the brain (cognitive neuroscience). Somewhat less prominent, but undeservedly so, is eye movement recording or eye-tracking. Eyetracking has a century-old history (Wade & Tatler, 2005) that has recently culminated in the widespread availability of relatively affordable and low-effort tools for the unobtrusive study of visual exploratory behaviour (e.g., Holmqvist et al., 2011). Eye movements, an endless succession of rapid jumps (saccades) and brief resting periods (fixations) of the eye balls, arguably constitute our most frequent goal-directed behaviour (cf. Desmurget, Pelisson, Rossetti, & Prablanc, 1998; Hayhoe & Ballard, 2005). Measurements of eye position can be taken several hundred times per second without requiring additional task instructions or interrupting the naturally occurring behaviour of participants. Successive measures with similar spatial coordinates are aggregated into one fixation with a specific location and duration; larger changes in location yield new fixations, and thus information about saccade directions and saccade sizes. Multiple fixations falling on a given visual object or area of interest can be further aggregated, resulting in gaze durations or total viewing times or dwell times as additional eye movement measures (Holmqvist et al., 2011). Importantly, just two simple assumptions about eye movement measures have allowed cognitive scientists to employ eye-tracking very productively in the service of cognitive research. First, gazing at something likely indicates the object of our thoughts (Tanenhaus, Spivey-Knowlton, Eberhard, & Sedivy, 1995). And secondly, the time spent looking at an object corresponds to the time we think about this object (Just & Carpenter, 1980). Both assumptions have received extensive support fromreading researchwheremostwords are successively fixated and fixation durations primarily reflect ease of comprehension (e.g., Kliegl, Nuthmann, & Engbert, 2006; Rayner, 1998; Rayner & Reingold, 2015; Reichle, Pollatsek, Fisher, & Rayner, 1998; Starr & Rayner, 2001). Building on these simple assumptions, eye-tracking thus provides detailed information about the spatial selectivity and temporal extent of ongoing cognition, enabling researchers to ‘‘read the mind’’. This research rationale can profitably be extended into the domain of numerical cognition. In this field of study the currently dominant view holds that number concepts are represented on a spatially oriented ‘‘mental number line’’, with small numbers represented to the left of larger numbers (at least in Western cultures; Dehaene, Bossini, & Giraux, 1993). The ‘‘mental number line’’ gives rise to spatial–numerical associations, which can be widely observed, both in simple number classification tasks and also in more complex tasks such as mental arithmetic (Fischer & Shaki, 2014). Eye movements provide online access to the focus of spatial attention and can therefore reveal the order and duration of concept activations, & Matthias Hartmann matthias.hartmann@psy.unibe.ch

Imagined paralysis impairs embodied spatial transformations

Recent studies showed that motor deficits and limb amputations selectively impair mental rotation of respective body parts. This is due to modifications in the body schema, which plays a pivotal role in bodily related mental spatial transformations. In the present study, we investigated whether imagined paralysis could affect mental transformations in healthy participants. Participants were required to make leg laterality judgments of imitable and non-imitable body postures that were presented at different orientations. Mental spatial transformation of imitable body posture relies on emulation processes, a mechanism through which the posture is covertly imitated by the observer. Imagined paralysis selectively impaired mental transformation of imitable body postures. These results reflect an inability to fully emulate stimulus postures, suggesting a modulation in the body schema. Our results show that the body schema incorporates top-down information about motoric constraints which can influence embodied cognition in healthy participants.