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Hans-Christoph Nuerk

Publications and source records attributed to Hans-Christoph Nuerk.

15 recordsLinked to original sources
PubMed2006

On the functional role of human parietal cortex in number processing: How gender mediates the impact of a 'virtual lesion' induced by rTMS.

Areas around the horizontal part of the intraparietal sulcus (hIPS) have repeatedly been reported to participate in processing numerical magnitude. Using transcranial magnetic stimulation (TMS), we investigated the functional role of the hIPS by examining two effects from the domain of numerical cognition: in magnitude comparison tasks response latencies are inversely related to the numerical distance between two numbers. This distance effect indexes access to the mental number representation. In magnitude comparison tasks responses are faster when decade and unit comparison would lead to the same decision (e.g. 42_57, 4 < 5 and 2 < 7) than when they would not (e.g. 47_62, 4 < 6 but 7 > 2). This compatibility effect reflects unit-decade integration processes. Differential susceptibility of (fe)male participants to TMS was examined. We applied repetitive TMS (rTMS; 1Hz for 10 min) over the left hIPS in 12 participants (6 female). No stimulation and vertex stimulation served as control conditions. The effect of rTMS was mediated by gender: in male participants, the distance effect decreased after TMS over hIPS. For female participants distance and compatibility effect both increased. This modulation of the compatibility effect was limited in duration to no more than 4 min. The hIPS seems to be functionally involved both in number magnitude processing and in integrating unit-decade magnitude information of two-digit numbers. Relative hemispheric specialization of the hIPS with respect to two-digit magnitude comparison is discussed.

Adult↗
PubMed2006

Crossed hands and the SNARC effect: a failure to replicate Dehaene, Bossini and Giraux (1993).

Dehaene et al. (1993, Experiment 6) presented evidence that the mental number line is left-to-right oriented with respect to representational associations and not with respect to left and right hands. Here we tried to replicate the study of Dehaene et al. (1993) in a larger sample (n = 32) using four different stimulus notations (Arabic numbers, number words, auditory number words, and dice patterns). As in the study by Dehaene et al. (1993), the spatial numerical association of response codes (SNARC) effect was examined with an incongruent hand assignment to left/right response keys (crossed hands). In contrast to Dehaene et al. (1993), we did not observe a SNARC effect in any condition. Power analyses revealed that n = 32 should have been large enough to detect SNARC effects of usual size. Furthermore, time-course analyses revealed no SNARC slope in faster and slower responses, so that the null effect could not be due to relatively slow responses with crossed hands. Joint analyses with previous data (Nuerk et al., 2005b) revealed significantly steeper SNARC slopes with congruent hand assignment, and no interaction between hand assignment and notation. Altogether, these findings suggest that the results of Dehaene et al. (1993) only hold under specific conditions. Differences between studies are discussed. We suggest that spatial context has an influence on the SNARC effect and that hand-based associations (and not only representational associations) are relevant for the SNARC effect.

Adolescent↗
PubMed2006

Effects of interhemispheric communication on two-digit arabic number processing.

We investigated interhemispheric communication and hemispheric style differences (analytic vs. holistic) in two-digit Arabic number comparison by employing the divided visual field paradigm. Interhemispheric communication modulated two-digit number comparison in a very specific way. While no advantage of interhemispheric communication was found with unit-decade compatible trials (e.g., 52 and 67, the decade comparison and unit comparison of the two numbers lead to the same response; see Nuerk et al., 2001), a significant advantage of interhemispheric interactions emerged in the attentionally more demanding incompatible trials (e.g., 47 and 62, decade and unit comparisons do not lead to the same response, because 4 < 6 but 7 > 2), thereby enhancing the efficiency of selective attention (c.f., Banich, 1998). Additionally, some results indicated a more analytical processing style in the left hemisphere and a relatively more holistic processing style in the right hemisphere.

Adolescent↗
PubMed2006

What makes multiplication facts difficult. Problem size or neighborhood consistency?

Two current models of arithmetic fact retrieval, the network interference theory (NIT; Campbell, 1995) and the interacting neighbors (IN) model (Verguts & Fias, 2005a), predict that errors in simple multiplication should be more probable, if they include the same digit as the correct result (i.e., if they are "consistent," compared with "inconsistent" errors). In a reanalysis of error data originally reported by Campbell (1997), we provide first empirical evidence for this prediction. Furthermore, these results support the notion of different quantity representations for decades and units as proposed by Nuerk, Weger, and Willmes (2001). However, the NIT and IN-model differ in their explanations of the problem-size effect, a hallmark finding robustly observed in arithmetic fact retrieval. Only the IN-model predicts that a correct answer's neighborhood consistency can fully account for the problem-size effect, which was confirmed in our analysis.

Attention↗
PubMed2006

Interference effects in a numerical Stroop paradigm in 9- to 12-year-old children with ADHD-C.

Attention deficit hyperactivity disorder (ADHD) is characterized by deficient self-regulation, poor attentional control, and poor response inhibition. To date, however, the extent to which these deficits affect basic interference control remains a matter of controversy. Secondly, ADHD has been reported to be associated with arithmetic deficits. It remains unclear whether such deficits are a secondary consequence of the above-mentioned characteristics of ADHD or whether basic numerical magnitude representations are also affected. In the present study we attempted to investigate these issues using a basic numerical interference paradigm. Nine- to twelve-year-old children with ADHD-C (attention-deficit hyperactivity-disorder combined type) and control children without ADHD (each n = 16) were presented with two digits of possibly different physical sizes (e.g., 3 7). This numerical Stroop task requires subjects to make a magnitude classification concerning either the physical or the numerical stimulus dimension. The irrelevant dimension can be congruent (same response), incongruent (different response), or neutral (no response association). Children with ADHD-C performed worse than control children in most analyses. The most important finding was a significant interaction of congruity effects with group in the numerical comparison task. Children with ADHD-C tended to show larger congruity and interference effects than controls, and these were not attributable to a speed-accuracy trade-off. The results might reflect differential processing speeds, or a different degree of automatic activation of physical and numerical magnitudes in children with and without ADHD-C. Alternative explanations, such as insufficient inhibition of selective (domain-specific) attention are also discussed.

Attention↗
PubMed2006

The influence of an external symbol system on number parity representation, or what's odd about 6?

The aim of this study was to investigate whether language-specific properties influence mental number processing. German Sign Language (DGS) numbers differ from those in spoken German not only in terms of modality but also in their basic language structure. A group of 20 congenitally deaf German signers participated in a number parity (odd/even) judgment task with DGS and printed German number words. The results indicated that two-handed DGS number signs are processed in a decomposed way. This language-specific effect also generalized to another linguistic number notation, German number words, but not to Arabic digit notation. These differences are discussed with respect to two possible routes to number parity.

Adult↗
PubMed2005

Neural representations of two-digit numbers: a parametric fMRI study.

When participants are asked to decide which of a pair of two-digit Arabic numbers is larger, they compare units and decades, even when units are irrelevant. Typically, behavioral responses are slower when units are incongruent with the decade comparison (e.g. 81_26, because 8 > 2 but 1 < 6; unit-decade compatibility effect, [Nuerk, H.-C., Weger, U., Willmes, K. 2001. Decade breaks in the mental number line? Putting the tens and units back in different bins. Cognition 82, B25-B33.]). We defined parametric regressors to examine the effect of decade digit distance and unit distance-based compatibility processing on the fMRI signal to investigate the neural correlates of two-digit magnitude processing. Fourteen male right-handed volunteers (mean age = 27, range 21-38 years) took part in the study. In a rapid event-related design, participants had to decide which of two two-digit Arabic numbers was larger. Data were preprocessed and analyzed statistically in SPM2. Activation in the anterior portion of the right IPS was significantly modulated by compatibility-based unit distance processing. Furthermore, decade distance predicted an increase in the fMRI signal from cortex around the left IPS, right anterior and right posterior IPS. These results indicate that magnitude representations of unit-decade compatibility and decade distance are subserved by the intraparietal cortex and that the symbolic structure of the Arabic number system is an important determinant of multi-digit number magnitude processing. Implications of the present results in terms of general symbolic information processing are discussed.

Adult↗
PubMed2005

A special role for numbers in working memory? An fMRI study.

Although numbers carry averbal semantics (i.e., magnitude), they are often utilized in verbal Working Memory (vWM) tasks. However, vWM is thought to rely on a purely phonological code. Here, we tested the influence of (a) averbal semantics and (b) different tasks on performance in a vWM context by examining stimulus and task-specific variation of activity in the horizontal parts of the intraparietal sulcus (hIPS). The hIPS has previously been shown to subserve magnitude processing modulated by (a) specific stimuli and (b) specific tasks. Two variants of an n-back paradigm (comparison and identity match tasks) utilizing letters and numbers as stimulus material at different levels of vWM load were administered in 16 participants. Behavioral and functional imaging data reveal stimulus-specific modulation of activity in the hIPS suggesting a semantic influence of numbers. In the identity match task, numbers induced additional hIPS activation compared to letters while letters never induced additional hIPS activation when compared to numbers. Letters as compared to numbers only induced additional hIPS activation in the comparison task. These results question the assumption of a purely phonological code in vWM because hIPS activation subserving magnitude processing is modulated by stimulus semantics and task demands.

Adult↗
PubMed2005

Language effects in magnitude comparison: small, but not irrelevant.

It is assumed that number magnitude comparison is performed by assessing magnitude representation on a single analog mental number line. However, we have observed a unit-decade-compatibility effect in German which is inconsistent with this assumption (Nuerk, Weger, & Willmes, 2001). Incompatible magnitude comparisons in which decade and unit comparisons lead to different responses (e.g., 37_52 for which 3<5, but 7>2) are slower and less accurately responded to than compatible trials in which decade and unit comparisons lead to the same response (e.g., 42_57, for which 4<5 and 2<7). As overall distance was held constant, a single holistic magnitude representation could not account for this compatibility effect. However, because of the inversion property of the corresponding German two-digit number words ("einundzwanzig" ), the language-generality of the effect is questionable. We have therefore examined the compatibility effect with native English speakers. We were able to replicate the compatibility effect using Arabic notation. Thus, the compatibility effect is not language-specific. However, in cross-linguistic analyses language-specific modulations were observed not only for number words but also for Arabic numbers. The constraints imposed on current models by the verbal mediation of Arabic number comparison are discussed.

Adult↗
PubMed2005

The universal SNARC effect: the association between number magnitude and space is amodal.

It is thought that number magnitude is represented in an abstract and amodal way on a left-to-right oriented mental number line. Major evidence for this idea has been provided by the SNARC effect (Dehaene, Bossini, & Giraux, 1993): responses to relatively larger numbers are faster for the right hand, those to smaller numbers for the left hand, even when number magnitude is irrelevant. The SNARC effect has been used to index automatic access to a central semantic and amodal magnitude representation. However, this assumption of modality independence has never been tested and it remains uncertain if the SNARC effect exists in other modalities in a similar way as in the visual modality. We have examined this question by systematically varying modality/notation (auditory number word, visual Arabic numeral, visual number word, visual dice pattern) in a within-participant design. The SNARC effect was found consistently for all modality/notation conditions, including auditory presentation. The size of the SNARC effect in the auditory condition did not differ from the SNARC effect in any visual condition. We conclude that the SNARC effect is indeed a general index of a central semantic and amodal number magnitude representation.

Adolescent↗
PubMed2004

On the perceptual generality of the unit-decade compatibility effect.

Number magnitude is assumed to be holistically represented along a single mental number line. Recently, we have observed a unit-decade-compatibility effect which is inconsistent with that assumption (Nuerk, Weger, & Willmes, 2001). In two-digit Arabic number comparison, we have demonstrated that compatible comparisons in which separate decade and unit comparisons lead to the same decision (32_47, 3 < 4 and 2 < 7) were faster than incompatible trials (37_52, 3 < 5, but 7 > 2). Because overall distance was matched, a holistic model could not account for the compatibility effect. However, one could argue that the compatibility effect was due to the specific vertical perceptual arrangement of the two-digit numbers in Nuerk et al.'s (2001) experiment where the decade digits and unit digits were presented column-wise above each other. To examine this objection, we studied the perceptual generality of the compatibility effect with diagonal presentation. We replicated the compatibility effect with diagonal presentation. It is concluded that the compatibility effect is not due to encoding characteristics imposed by the perceptual setting of the original experiment. In particular, the assumption of an overall analog magnitude representation for two-digit numbers is not consistent with these data.

Adult↗
PubMed2004

On the development of the mental number line: more, less, or never holistic with increasing age?

Magnitude is assumed to be represented along a holistic mental number line in adults. However, the authors recently observed a unit-decade compatibility effect for 2-digit numbers that is inconsistent with this "holisticness" assumption (H.-C. Nuerk, U. Weger, & K. Willmes, 2001). This study used the compatibility effect to examine whether the mental number line representation of magnitude changes toward greater or less holisticness in children from Grades 2-5. The results indicate that decades and units of 2-digit numbers are processed separately rather than holistically from Grade 2 on. However, this separate processing seems to develop from a more sequential (left-to-right) to a more parallel processing mode. Moreover, children may use different strategies depending on task demands. The results are interpreted in the framework of Siegler's overlapping waves model.

Child↗
PubMed2004

Notational modulation of the SNARC and the MARC (linguistic markedness of response codes) effect.

Number magnitude and number parity representation are fundamental number representations. However, the representation of parity is much less understood than that of magnitude: Therefore, we investigated it by examining the (new) Linguistic Markedness of Response Codes (MARC) effect: Responses are facilitated if stimuli and response codes both have the same (congruent) linguistic markedness (even-right, odd-left) while incongruent conditions (even-left, odd-right) lead to interference. We examined systematically the MARC (for parity) and the Spatial Numerical Association of Response Codes (SNARC; for magnitude) effect for different number notations (positive Arabic, negative Arabic, number words) and with different methods of data analysis. In a parity judgement task, the SNARCeffect indicating a magnitude representation was replicated for all notations except for negative numerals. The MARCeffect was found for number words in all analyses, but less consistently for the other notations. In contrast, a correlational analysis of the reaction time (RT) data, as suggested by Sternberg (1969) using a nonmetric multi-dimensional scaling (MDS) procedure, produced a clear association of parity and response code for all notations (MARCeffect), but little evidence of the SNARCeffect. We discuss the extent to which these notation-specific MARC and SNARC effects constrain current models of number processing and elaborate on the possible functional locus of the MARC effect.

Adult↗
PubMed2002

On the impact of different number representations in the number bisection task.

The number bisection task--in which the numerical middle of two other numbers has to be determined (e.g., 6 is the numerical middle of 4 and 8)--has recently been used in neuropsychological case studies in addition to the number comparison task to assess quantitative capabilities in number processing. While factors determining difficulty in normal participants have often been systematically investigated in the number comparison task, this has not yet been done in the number bisection task. Based on a pilot study by van Herten (1999), we extracted four factors that we hypothesized to modulate difficulty in a verification version of the number bisection task in normal participants: Multiplicativity (whether or not the three numbers are part of a multiplication table), range (distance between the smallest and the largest number) for bisectable number triplets as well as distance of the middle number to the numerical middle, and bisection possibility for non-bisectable triplets. In the current study, we obtained large effects for all four factors on RT and accuracy data and some interesting interactions in normal participants. In a regression analysis, we additionally observed inhibitory effects of decade crossing and of ten inclusion (whether or not one of the three numbers was a decade number). We discuss the impact of these results for the use of the number bisection task as an assessment tool in neuropsychology. Finally, we examine the consequences of these results for models of number processing.

Adult↗