Department of Neurology

Cohen Kadosh found that Hebrew number words and Arabic digits elicited different distance effects. The numerical distance effect (i.e., faster reaction times and smaller error rates for numbers with larger distance to a standard number, e.g., 5) was smaller for number words than for digits. The author suggested that the result indicated a notation-dependent (i.e., nonabstract) numerical representation. Alternatively, however, it is possible that the distance effect was decreased by perceptual features of the Hebrew number words used as stimuli. To test this hypothesis, we replicated the study of Cohen Kadosh, but with English and Turkish number words compared to Arabic digits. The perceptual features of Turkish number words lead to the hypothesis that the opposite effect should be present: an increased distance effect for number words compared to Arabic digits. On the other hand, English number words show features similar to those of Hebrew number words, thus leading to the expectation of a decreased distance effect for them. Our results confirmed our hypotheses. We conclude that the distance effect can be influenced also by perceptual features in addition to the impact of numerical representations.

The approximate number system (ANS) has been consistently found to be associated with math achievement. However, little is known about the interactions between the different instantiations of the ANS and in how many ways they are related to exact calculation. In a cross-sectional design, we investigated the relationship between three measures of ANS acuity (non-symbolic comparison, non-symbolic estimation and non-symbolic addition), their cross-sectional trajectories and specific contributions to exact calculation. Children with mathematical difficulties (MD) and typically achieving (TA) controls attending the first six years of formal schooling participated in the study. The MD group exhibited impairments in multiple instantiations of the ANS compared to their TA peers. The ANS acuity measured by all three tasks positively correlated with age in TA children, while no correlation was found between non-symbolic comparison and age in the MD group. The measures of ANS acuity significan...

Gender differences in numerical domains have frequently been reported, but typically only from high-school age onwards. Recently, we found performance differences in favor of primary school boys in multi-digit number processing. Several underlying factors have been suggested to explain general differences in multi-digit number processing (such as visual-spatial working memory capacity), gender differences in mathematics (such as attitudes toward mathematics),

There is evidence for a systematic association of numbers and space. A prominent finding supporting this notion is the spatial-numerical association of response codes (SNARC) effect describing relatively faster responses to smaller numbers using a left-hand key and to larger numbers using a right-hand key. However, the assumption of the SNARC effect reflecting spatial-numerical associations was challenged recently. A working memory account was proposed suggesting that not numbers per se but their position in a memorized sequence is associated with space. Yet, there is also first evidence suggesting that this ordinal position and the SNARC effect may not be mutually exclusive. In the present study, we further examined the relationship between the ordinal position and the SNARC effect. We manipulated the number of items in the memorized ordered sequence and the number range employed. Results revealed both a significant ordinal position effect, but also a significant SNARC effect, substantiating the view that both effects are not mutually exclusive but may co-exist. Furthermore, we found that the SNARC effect was reduced when numbers ranging from 1 to 10 versus numbers ranging from 1 to 9 were employed. Thus, our results question a pure working memory account for the SNARC effect. Additionally, they highlight the critical role of the number range employed in research about the SNARC effect.

Performance decrements attributed to mental fatigue have been found to be especially pronounced in tasks that involve the voluntary control of attention. Here we explored whether mental fatigue from prolonged time on task (TOT) also impairs temporal preparation for speeded action in a simple reaction-time task. Temporal preparation is enabled by a warning signal presented before the imperative stimulus and usually results in shorter reaction time (RT). When the delay between warning and imperative stimuli - the foreperiod (FP) - varies between trials, responses are faster with longer FPs. This pattern has been proposed to arise from either voluntary attentional processes (temporal orienting) or automatic trial-to-trial learning (trace conditioning). The former account suggests a selective RT increase on long-FP trials with fatigue; the latter account suggests no such change. Over a work period of 51 min, we found the typical increase in overall RT but no selective RT increase after long FPs. This additivity indicates that TOT-induced mental fatigue generally reduces cognitive efficiency but leaves temporal preparation under time uncertainty unaffected. We consider this result more consistent with the trace-conditioning account of temporal preparation.

1 Multi-Digit Number Processing Hans-Christoph Nuerk, Klaus Willmes, and Martin H. Fischer ... 3 Extending the Mental Number Line: A Review of Multi-Digit Number Processing Hans-Christoph Nuerk, Korbinian Moeller, Elise Klein, Klaus Willmes, and Martin H. Fischer ... 23 Sequential Processing of Two-Digit Numbers: Evidence of Decomposition From a Perceptual Number Matching Task Javier Garcıa-Orza and Jesús Damas 30 Digit Repetition Effect in Two-Digit Number Comparison Simone Gazzellini and Alessandro Laudanna 37 The Processing of Two-Digit Numbers ...