Analytic model for the line tension of a bowing dislocation segment

The resistance of a dislocation to bowing under stress governs the strength of the gamut of metallic material systems. This resistance is commonly referred to as the dislocation line tension (Γ) and is employed ubiquitously within continuum scale models of metal plasticity. Despite its significance, a unifying model for the line tension of a bowing dislocation segment, which has been analytically derived and independently reproduces simulation results, remains lacking. Here, we report a model for Γ of a curved, semicircular bowing dislocation segment. Upon applying our model to the operative stress of a Frank–Read dislocation source, we predict a prelogarithmic scaling of the Frank–Read source strength in agreement with existing simulation results. Moreover, in the limit of infinitesimal bowout we predict a prelogarithmic line tension factor which also agrees with theoretical analyses. Our model provides insight into the evolution of an arbitrarily oriented, stressed dislocation segment without resorting to numerical methods.     

线条朝向的空间构型对视觉工作记忆表征的影响

采用行为实验和事件相关电位技术(ERP),通过整体检测的变化觉察范式,探讨线条朝向的空间构型对视觉工作记忆表征的影响及机制。行为结果发现,水平排列线条朝向的视觉工作记忆成绩高于杂乱排列; 水平排列线条朝向有框时的视觉工作记忆成绩低于无框条件; ERP结果发现,无框条件下水平排列的线条朝向诱发的对侧延迟活动的波幅小于有框条件。以上结果说明,水平排列的空间构型能够促进线条朝向的视觉工作记忆表征,这一促进作用的潜在机制可能是水平排列的空间构型能够降低信息表征的负荷。     

Unconscious semantic categorization and mask interactions: An elaborate response to Kunde et al. (2005)

In their original report [Kunde, W., Kiesel, A., & Hoffmann, J. (2003). Conscious control over the content of unconscious cognition. Cognition, 88, 223-242] maintain that “unconscious stimuli [do not] owe their impact […] to automatic semantic categorization” (p.223), and instead propose the action-trigger theory of unconscious priming. In a reply to our paper [Kunde, W., Kiesel, A., & Hoffmann, J. (2005). On the masking and disclosure of unconscious semantic processing. A reply to Van Opstal, Reynvoet, & Verguts (2005). Cognition], the authors adopt a reconcilist position, and propose that both theories may be valid depending on the experimental situation. We discuss the evidence in favor of this position. [Kunde, W., Kiesel, A., & Hoffmann, J. (2005). On the masking and disclosure of unconscious semantic processing. A reply to Van Opstal, Reynvoet, & Verguts (2005). Cognition] also propose an alternative account of our mask-type blocking hypothesis. We report an experiment that distinguishes between our original and their alternative hypothesis.     

Do children learn the integers by induction?

According to one theory about how children learn the meaning of the words for the positive integers, they first learn that "one," "two," and "three" stand for appropriately sized sets. They then conclude by inductive inference that the next numeral in the count sequence denotes the size of sets containing one more object than the size denoted by the preceding numeral. We have previously argued, however, that the conclusion of this Induction does not distinguish the standard meaning of the integers from nonstandard meanings in which, for example, "ten" could mean set sizes of 10, 20, 30,... elements. Margolis and Laurence [Margolis, E., & Laurence, S. (2008). How to learn the natural numbers: Inductive inference and the acquisition of number concepts. Cognition, 106, 924-939] believe that our argument depends on attributing to children "radically indeterminate" concepts. We show, first, that our conclusion is compatible with perfectly determinate meanings for "one" through "three." Second, although the inductive inference is indeed indeterminate - which is why it is consistent with nonstandard meanings - making it determinate presupposes the constraints that the inference is supposed to produce.     

Children's Understanding of the Natural Numbers’ Structure

When young children attempt to locate numbers along a number line, they show logarithmic (or other compressive) placement. For example, the distance between “5” and “10” is larger than the distance between “75” and “80.” This has often been explained by assuming that children have a logarithmically scaled mental representation of number (e.g., Berteletti, Lucangeli, Piazza, Dehaene, & Zorzi, 2010 ; Siegler & Opfer, 2003 ). However, several investigators have questioned this argument (e.g., Barth & Paladino, 2011 ; Cantlon, Cordes, Libertus, & Brannon, 2009 ; Cohen & Blanc‐Goldhammer, 2011 ). We show here that children prefer linear number lines over logarithmic lines when they do not have to deal with the meanings of individual numerals (i.e., number symbols, such as “5” or “80”). In Experiments 1 and 2, when 5‐ and 6‐year‐olds choose between number lines in a forced‐choice task, they prefer linear to logarithmic and exponential displays. However, this preference does not persist when Experiment 3 presents the same lines without reference to numbers, and children simply choose which line they like best. In Experiments 4 and 5, children position beads on a number line to indicate how the integers 1–100 are arranged. The bead placement of 4‐ and 5‐year‐olds is better fit by a linear than by a logarithmic model. We argue that previous results from the number‐line task may depend on strategies specific to the task.     

Spontaneous focusing on numerosity as a domain-specific predictor of arithmetical skills

The aim of this 2 year longitudinal study was to explore whether children’s individual differences in spontaneous focusing on numerosity (SFON) in kindergarten predict arithmetical and reading skills 2 years later in school. Moreover, we investigated whether the positive relationship between SFON and mathematical skills is explained by children’s individual differences in spontaneous focusing on a non-numerical aspect. The participants were 139 Finnish-speaking children. The results show that SFON tendency in kindergarten is a significant domain-specific predictor of arithmetical skills, but not reading skills, assessed at the end of Grade 2. In addition, the relationship between SFON and number sequence skills in kindergarten is not explained by children’s individual differences in their focusing on a non-numerical aspect that is, spatial locations.     

Predicting sights from sounds: 6-month-olds' intermodal numerical abilities

Although the psychophysics of infants’ nonsymbolic number representations have been well studied, less is known about other characteristics of the approximate number system (ANS) in young children. Here three experiments explored the extent to which the ANS yields abstract representations by testing infants’ ability to transfer approximate number representations across sensory modalities. These experiments showed that 6-month-olds matched the approximate number of sounds they heard to the approximate number of sights they saw, looking longer at visual arrays that numerically mismatched a previously heard auditory sequence. This looking preference was observed when sights and sounds mismatched by 1:3 and 1:2 ratios but not by a 2:3 ratio. These findings suggest that infants can compare numerical information obtained in different modalities using representations stored in memory. Furthermore, the acuity of 6-month-olds’ comparisons of intermodal numerical sequences appears to parallel that of their comparisons of unimodal sequences.     

Place‐value understanding in number line estimation predicts future arithmetic performance

In multi‐digit numbers, the value of each digit is determined by its position within the digit string. Children's understanding of this place‐value structure constitutes a building block for later arithmetic skills. We investigated whether a number line estimation task can provide an assessment of place‐value understanding in first grade. We hypothesized that estimating the position of two‐digit numbers requires place‐value understanding. Therefore, we fitted a linear function to children's estimates of two‐digit numbers and considered the resulting slope as a measure of children's place‐value understanding. We observed a significant correlation between this slope and children's performance in a transcoding task known to require place‐value understanding. Additionally, the slope for two‐digit numbers assessed at the beginning of grade 1 predicted children's arithmetic performance at the end of grade 1. These results indicate that the number line estimation task may indeed constitute a valid measure for first‐graders' place‐value understanding. Moreover, these findings are hard to reconcile with the view that number line estimation directly assesses a spatial representation of numbers. Instead, our results suggest that numerical processes involved in performing the task (such as place‐value understanding) may drive the association between number line estimation and arithmetic performance.     

Groups and Plane Geometry

We show that the first-order theory of a large class of plane geometries and the first-order theory of their groups of motions, understood both as groups with a unary predicate singling out line-reflections, and as groups acting on sets, are mutually inter-pretable. Presented by Robert Goldblatt