Cardinal and ordinal processing in spatial neglect

Poster (2016, January)

Patients with spatial neglect do not only have difficulties in orienting attention in physical space but also in representational space, especially with respect to the mental representation of numbers ... [more ▼]

Patients with spatial neglect do not only have difficulties in orienting attention in physical space but also in representational space, especially with respect to the mental representation of numbers. Indeed, in a study by Zorzi et al. (2012) neglect patients were particularly slow when asked to compare the number 4 to the standard number 5, suggesting difficulties to process numbers on the left side of an internal standard. This difficulty was observed in a magnitude judgement, but not in a parity task, implying a dissociation between explicit and implicit processing of numerical magnitude. The present study aimed at replicating these findings and extending them to non-numerical sequences in order to complement the data obtained on bisection tasks (Zamarian, et al., 2007). Sixteen right-sided brain damaged patients with neglect (N+ =6; 4 females; all right handers; mean age: 55 +/- 8,7) and without neglect (N- =10; 2 females; all right hander; mean age: 48 +/- 6.2) participated in the study. They were administered the following tasks: a magnitude and a parity judgement task; an ordinal judgement task on numbers and on letters and a consonant/vowel classification task. For each task and each patient, a linear regression was computed in which the difference between the response times for the left effector (index finger) and the right effector (middle finger) was predicted by number magnitude. A negative slope will indicate the presence of a SNARC-like effect. We compared the negative slopes of the two patient groups using a Chi-square. Considering the proportion of SNARC-like effects, it appeared that, on one hand, N+ patients showed fewer SNARC-like effects than N- patients during magnitude judgements on numbers. Thus confirming the findings by Zorzi et al. (2012). On the other hand, N+ patients behaved similarly to N- patients for the parity judgements on numbers and for the order judgements both on numbers and letters. This last result suggest a dissociation between the spatial representation of magnitude and of order in N+ patients. These results point towards a specific impairment in explicit access to number magnitude in spatial hemineglect. [less ▲]

Canonical finger numeral configurations are perceived holistically

Poster (2014, April 04)

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 ▲]

Numbers reorient visuo-spatial attention during cancellation tasks

in Experimental Brain Research (2013), 225(4), 549-57

Numbers induce shifts of spatial attention on the left or the right sides of external space as a function of their magnitude. However, whether this number-space association is restricted to the linear ... [more ▼]

Numbers induce shifts of spatial attention on the left or the right sides of external space as a function of their magnitude. However, whether this number-space association is restricted to the linear horizontal extensions, or extends to the whole visual scene, is still an open question. This study investigates, by means of a cancellation paradigm, the influence of numerical magnitude during scanning tasks in which participants freely explore complex visual scenes unconstrained towards either the horizontal or the vertical unidimensional axes. Five cancellation tasks were adapted in which Arabic digits were used as targets or distracters, in structured (lines and columns) or unstructured visual displays, with a smaller (2 or 3 types of distracters) or larger (10 or more types of distracters) sets of stimuli. Results show that the participants' hits distribution was a function of number magnitude: shifted on the left for small and on the right for large numbers. This effect was maximised when numerical cues were sparse, randomly arranged and, critically, irrelevant to the task. Overall, this study provides novel evidence from visuo-spatial exploratory cancellation tasks for an attentional shift induced by number magnitude. [less ▲]

Place and summation coding for canonical and non-canonical finger numeral representations

in Cognition (2010), 117(1), 95-100

Fingers can be used to express numerical magnitudes, and cultural habits about the fixed order in which fingers are raised determine which configurations become canonical and which non-canonical. Although ... [more ▼]

Fingers can be used to express numerical magnitudes, and cultural habits about the fixed order in which fingers are raised determine which configurations become canonical and which non-canonical. Although both types of configuration carry magnitude information, it has been shown that the canonical ones are recognized faster and directly linked to number semantics. Here we tested whether this difference is a consequence of differences in the qualitative way of processing the two types of configurations. When participants named Arabic digits (Experiment 1) or verbal numerals (Experiment 2) primed by canonical and non-canonical finger configurations, qualitatively different priming patterns were observed for the two types of configurations. Canonical configurations activated a place coding representation, with priming spreading to close smaller and larger magnitudes as a function of the prime-target distance. Conversely, non-canonical configurations activated a summation coding representation priming smaller and equal magnitudes independently of the prime-target distance, and larger targets depending on this distance. [less ▲]

Let us redeploy attention to sensorimotor experience

in Behavioral and Brain Sciences (2010), 33(4), 283

With his massive redeployment hypothesis (MRH), Anderson claims that novel cognitive functions are likely to rely on pre-existing circuits already possessing suitable resources. Here, we put forward ... [more ▼]

With his massive redeployment hypothesis (MRH), Anderson claims that novel cognitive functions are likely to rely on pre-existing circuits already possessing suitable resources. Here, we put forward recent findings from studies in numerical cognition in order to show that the role of sensorimotor experience in the ontogenetical development of a new function has been largely underestimated in Anderson’s proposal. [less ▲]

Finger counting: The missing tool?

in Behavioral and Brain Sciences (2008), 31

Rips et al. claim that the principles underlying the structure of natural numbers cannot be inferred from interactions with the physical world. However, they failed to consider an important source of ... [more ▼]

Rips et al. claim that the principles underlying the structure of natural numbers cannot be inferred from interactions with the physical world. However, they failed to consider an important source of interaction: finger counting. Here, we show that finger counting satisfies all the conditions required for allowing the concept of numbers to emerge from sensorimotor experience through a bottom-up process. [less ▲]

Finger-digit compatibility in Arabic numeral processing

in Quarterly Journal of Experimental Physiology (2006), 59(9), 1648-63

Finger-digit response compatibility was tested by asking participants to identify Arabic digits by pressing one of ten keys with all ten fingers. The direction of the finger-digit mapping was varied by ... [more ▼]

Finger-digit response compatibility was tested by asking participants to identify Arabic digits by pressing one of ten keys with all ten fingers. The direction of the finger-digit mapping was varied by manipulating the global direction of the hand-digit mapping as well as the direction of the finger-digit mapping within each hand (in each case, from small to large digits, or the reverse). The hypothesis of a left-to-right mental number line predicted that a complete left-to-right mapping should be easier whereas the hypothesis of a representation based on finger counting predicted that a counting-congruent mapping should be easier. The results show that a mapping congruent with the prototypical finger-counting strategy reported by the participants leads to better performance than a mapping congruent with a left-to-right oriented mental number line, and demonstrate that finger-counting strategies clearly influence the way numerical information is mentally represented and processed. [less ▲]