Different number-processing tasks entail qualitatively different SNARC effects

Poster (2014, October)

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times to small/large digits with the left/right hand ... [more ▼]

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times to small/large digits with the left/right hand respectively. Although the SNARC effect has been extensively replicated, it is characterized by high inter-individual variability (e.g. Hoffmann et al., 2014). Moreover, even though number-space associations have been observed when numerical magnitude is both relevant (e.g. magnitude comparison) and irrelevant (e.g. parity and color judgment) for successful task completion, their strengths and underlying cognitive processes seem to vary depending on whether explicit reference to numerical magnitude is drawn or not (Fias et al., 2001; Mitchell et al., 2012). To further evaluate this hypothesis, we examined whether the SNARC effects observed in a single individual during distinct number-processing tasks were systematically linked. We computed correlations between the SNARC effects measured during a parity, magnitude and color judgment task in a population of 85 healthy university students (39 females, mean age=23.44 years). Interestingly, no relation could be observed between the color (slope=-6.79) and magnitude SNARC effects (slope=-6.98; r=0.18, p=0.11), indicating that number-space associations potentially underlie different cognitive operations in tasks with and without explicit numerical magnitude processing. Conversely, the parity SNARC effect (slope=-11.58) correlated with both the color (r=0.36, p=0.001) and magnitude SNARC effects (r=0.36, p=0.001). This suggests that although no explicit numerical magnitude treatment is required in the parity task – explaining its relationship with the color task – the involvement of number semantics is sufficient to position it in line with the magnitude judgment task. [less ▲]

Que fait un professeur d’université qui travaille dans le domaine des neurosciences cognitives?

Conference given outside the academic context (2014)

Cognitive style influences number-space associations

Poster (2014, May)

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times to small/large digits with the left/right hand ... [more ▼]

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times to small/large digits with the left/right hand respectively. The cognitive processes underlying the SNARC effect are suggested to be task-dependent, such that number-space interactions result from verbal-spatial and visual-spatial number coding in parity and magnitude judgment tasks respectively (van Dijck et al., 2009). Moreover, the SNARC effect is characterized by high inter-individual variability (Hoffmann et al., 2014). Here we aimed to determine whether differences between the cognitive styles of individuals could influence the SNARC effect in a parity and magnitude judgment task. To distinguish between verbal and visual cognitive styles and between object- and spatial-visualizers, participants (n=74, 36 females, mean age=23.45 years) completed a modified version of Kirby et al.’s (1988) Verbalizer-Visualizer Questionnaire (VVQ, as in Mendelson & Thorson, 2004) and the Object-Spatial Imagery Questionnaire (OSIQ, Blajenkova et al., 2006, purchased from MM Virtual Design, LLC) respectively. Each item was placed on a five-point rating scale between strongly agree and strongly disagree, allowing us to compute verbal, visual, object and spatial scores for each participant. Participants that featured visual/verbal and spatial/object score ratios that were either both below or above the respective median ratio (visual/verbal ratio: M=1.09; spatial/object ratio: M=0.87) were classified as verbalizers (n=25, 16 females) and spatial-visualizers (n=25, 10 females) respectively. Participants subsequently performed the classical parity and magnitude judgment tasks. In verbalizers, the SNARC effect was significantly negative in the parity (slope=-11.2, p=0.001), but not the magnitude judgment task (slope=-1.2, p=0.53). Their verbal cognitive style might thus have induced a strong number-space association in tasks that supposedly draw on these cognitive processes, while it prevented spatial-numerical interactions in tasks that activate visuo-spatial number coding. Conversely, spatial-visualizers featured a significantly negative magnitude SNARC effect (slope=-4.8, p=0.04), indicating that a visuo-spatial style is not only necessary but sufficient to generate a number-space association in tasks that favour visuo-spatial number coding. Interestingly, they also manifested a significantly negative parity SNARC effect (slope=-9.9, p<0.001). It is likely that the spatial-visualizers switched strategy for the parity judgment task and - despite their visuo-spatial preferences - adopted the better-suited verbal strategy. Indeed, in contrast to verbalizers, their parity and magnitude SNARC effects did not correlate (spatial-visualizers: r=0.14, p=0.5; verbalizers: r=0.4, p=0.05). All in all, differences in cognitive styles might provide an additional explanation for the high inter-individual variability of the SNARC effect. Moreover, we provided further evidence for the verbal-spatial and visuo-spatial nature of the parity and magnitude SNARC effects respectively. [less ▲]

Are patients with Parkinson’s disease blind to blindsight?

in Brain : A Journal of Neurology (2014)

In Parkinson’s disease, visual dysfunction is prominent. Visual hallucinations can be a major hallmark of late stage disease, but numerous visual deficits also occur in early stage Parkinson’s disease ... [more ▼]

In Parkinson’s disease, visual dysfunction is prominent. Visual hallucinations can be a major hallmark of late stage disease, but numerous visual deficits also occur in early stage Parkinson’s disease. Specific retinopathy, deficits in the primary visual pathway and the secondary ventral and dorsal pathways, as well as dysfunction of the attention pathways have all been posited as causes of hallucinations in Parkinson’s disease. We present data from patients with Parkinson’s disease that contrast with a known neuro-ophthalmological syndrome, termed ‘blindsight’. In this syndrome, there is an absence of conscious object identification, but preserved ‘guess’ of the location of a stimulus, preserved reflexive saccades and motion perception and preserved autonomical and expressive reactions to negative emotional facial expressions. We propose that patients with Parkinson’s disease have the converse of blindsight, being ‘blind to blindsight’. As such they preserve conscious vision, but show erroneous ‘guess’ localization of visual stimuli, poor saccades and motion perception, and poor emotional face perception with blunted autonomic reaction. Although a large data set on these deficits in Parkinson’s disease has been accumulated, consolidation into one specific syndrome has not been proposed. Focusing on neuropathological and physiological data from two phylogenetically old and subconscious pathways, the retino-colliculo-thalamo-amygdala and the retino-geniculo-extrastriate pathways, we propose that aberrant function of these systems, including pathologically inhibited superior colliculus activity, deficient corollary discharges to the frontal eye fields, dysfunctional pulvinar, claustrum and amygdaloid subnuclei of the amygdala, the latter progressively burdened with Lewy bodies, underlie this syndrome. These network impairments are further corroborated by the concept of the ‘silent amygdala’. Functionally being ‘blind to blindsight’ may facilitate the highly distinctive ‘presence’ or ‘passage’ hallucinations of Parkinson’s disease and can help to explain handicaps in driving capacities and dysfunctional ‘theory of mind’. We propose this synthesis to prompt refined neuropathological and neuroimaging studies on the pivotal nuclei in these pathways in order to better understand the networks underpinning this newly conceptualized syndrome in Parkinson’s disease. [less ▲]

Predicting first-grade mathematics achievement: the contributions of domain-general cognitive abilities, nonverbal number sense, and early number competence

in Frontiers in Psychology (2014), 5

Early number competence, grounded in number-specific and domain-general abilities, is supposed to lay the foundation for later math achievement. Few longitudinal studies tested a comprehensive model for ... [more ▼]

Early number competence, grounded in number-specific and domain-general abilities, is supposed to lay the foundation for later math achievement. Few longitudinal studies tested a comprehensive model for early math development. Using structural equation modeling and mediation analyses, we studied the influence of kindergarteners’ basic cognitive abilities (i.e., nonverbal number sense, working memory, fluid intelligence, and receptive vocabulary) and their early number competence (i.e., symbolic number skills) on first grade math achievement (arithmetic, shape and space, and number line estimation) assessed one year later. Latent regression models revealed that nonverbal number sense and working memory are central building blocks for developing early number competence in kindergarten and that early number competence is key for first grade math achievement. Fluid intelligence significantly predicted arithmetic and number line estimation while receptive vocabulary significantly predicted shape and space after controlling for early number competence. In sum we suggest that early math achievement draws on different constellations of number-specific and domain-general mechanisms. [less ▲]

Task instructions determine the visuo-spatial and verbal-spatial nature of number-space associations

Poster (2014, April)

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times (RTs) to small/large digits with the left/right ... [more ▼]

Evidence for number-space associations comes from the spatial-numerical association of response-codes (SNARC) effect, consisting in faster reaction times (RTs) to small/large digits with the left/right hand respectively. Classically, they are thought to result from numerical coding along a left-to-right-oriented mental number line (visuo-spatial account; Dehaene et al., 1993). Recently, an association between the verbal concepts “small”/“left” and “large”/“right” has been suggested as an alternative explanation (verbal-spatial account; Gevers et al., 2010). Since the predominance of these accounts remains debated, we aimed to determine whether task instructions influence their extent of explaining the SNARC effect. A magnitude comparison task where the verbal labels “left”/“right” were displayed on the left/right response side alternatively allowed us to directly contrast the two accounts by comparing verbal SNARC slopes (based on differences in RTs to the labels “left” and “right”) with classical spatial SNARC slopes (based on differences in RTs to the left and right response side). In the verbal condition, participants (41 students, 20 female, mean age=21.6) responded to the assigned labels irrespective of their side of appearance, whereas the spatial condition required responding to the left or right response side irrespective of the displayed label. Under verbal instructions, only the verbal slope was significantly negative (verbal slope=-67.54, spatial slope=-4.82). Conversely, no significant difference was observed between verbal and spatial slopes under spatial instructions – both slopes being significantly negative (verbal slope=-15.12, spatial slope=-29.39). Taken together, number-space associations arise from verbal coding regardless of task instructions, while spatial coding only occurs under spatial instructions. [less ▲]

The Impact of Mathematical Proficiency on the Number-Space Association

in PLoS ONE (2014)

A specific instance of the association between numerical and spatial representations is the SNARC (Spatial Numerical Association of Response Codes) effect. The SNARC effect describes the finding that ... [more ▼]

A specific instance of the association between numerical and spatial representations is the SNARC (Spatial Numerical Association of Response Codes) effect. The SNARC effect describes the finding that during binary classification of numbers participants are faster to respond to small/large numbers with the left/right hand respectively. Even though it has been frequently replicated, important inter-individual variability has also been reported. Mathematical proficiency is an obvious candidate source for inter-individual variability in numerical judgments, but studies investigating its influence on the SNARC effect remain scarce. The present experiment included a total of 95 University students, divided into three groups differing significantly in their mathematical proficiency levels. Using group analyses, it appeared that the three groups differed significantly in the strength of their number-space associations in a parity judgment task. This result was further confirmed on an individual level, with higher levels in arithmetic leading to relatively weaker SNARC effects. To explain this negative relationship we propose accounts based on differences in access to qualitatively different numerical representations and also consider more domain general factors, with a focus on inhibition capacities. [less ▲]

Language influences number processing: the case of bilingual Luxembourg

Scientific Conference (2014)

Canonical finger numeral configurations are perceived holistically

Poster (2014)

Sooner or later human beings represent or see numerosities represented by hands. This handling of small numerosities by prototypical finger configurations has been the focus of many experiments ... [more ▼]

Sooner or later human beings represent or see numerosities represented by hands. This handling of small numerosities by prototypical finger configurations has been the focus of many experiments investigating the possibility that semantic representations of numbers are motor-rooted. Canonical finger configurations (i.e. the culturally determined way to express numerosity with fingers) are for instance recognized faster (Di Luca et al., 2006), and give direct access to number semantics (Di Luca et Pesenti, 2008). It is also known that these effects are not due to a visual facilitation of canonical configurations (Di Luca et Pesenti, 2010), but to a different inner representation (Di Luca, Lefèvre and Pesenti, 2010). However, a precise characterization of their visual processing is currently lacking. We addressed this shortcoming by using an eye-tracking method based on gaze-contingent stimulus presentation (Van Belle et al., 2010). While participants named numerosities expressed by canonical and non-canonical finger numeral configurations presented in upright or inverted orientations, we selectively impaired analytical or holistic visual perception by respectively masking (in real time) peripheral or focal vision. Our data confirm the results found in literature: canonical configurations are processed faster than non-canonical ones, upright configurations are processed faster than inverted ones and holistic perception is faster than analytical one. Most importantly, we also demonstrate that canonical configurations are impaired by the peripheral mask (i.e. holistic vision hindered) whereas non-canonical ones are impaired by the foveal mask (i.e. analytical vision hindered). These results confirm that the practice of finger numeral configurations modifies not only the way human beings process and represent numerosities but especially the way to visually perceive them. [less ▲]

The impact of inhibition capacities and age on number–space associations.

in Cognitive Processing (2014)

Numerical and spatial representations are tightly linked, i.e., when doing a binary classification judgment on Arabic digits, participants are faster to respond with their left/right hand to small/large ... [more ▼]

Numerical and spatial representations are tightly linked, i.e., when doing a binary classification judgment on Arabic digits, participants are faster to respond with their left/right hand to small/large numbers, respectively (Spatial-Numerical Association of Response Codes, SNARC effect, Dehaene et al. in J Exp Psychol Gen 122:371–396, 1993). To understand the underlying mechanisms of the well-established SNARC effect, it seems essential to explore the considerable inter-individual variability characterizing it. The present study assesses the respective roles of inhibition, age, working memory (WM) and response speed. Whereas these non-numerical factors have been proposed as potentially important factors to explain individual differences in SNARC effects, none (except response speed) has so far been explored directly. Confirming our hypotheses, the results show that the SNARC effect was stronger in participants that had weaker inhibition abilities (as assessed by the Stroop task), were relatively older and had longer response times. Interestingly, whereas a significant part of the age influence was mediated by cognitive inhibition, age also directly impacted the SNARC effect. Similarly, cognitive inhibition abilities explained inter-individual variability in number– space associations over and above the factors age, WM capacity and response speed. Taken together our results provide new insights into the nature of number–space associations by describing how these are influenced by the non-numerical factors age and inhibition. [less ▲]