Number-form synesthetes consciously experience numbers in spatially-defined locations. For non-synesthete individuals, a similar association of numbers and space appears in the form of an implicit mental number line as signified by the distance effect–reaction time decreases as the numerical distance between compared numbers increases. In the current experiment, three number-form synesthetes and two different non-synesthete control groups performed a number comparison task. Synesthete participants exhibited a sizeable distance effect only when presented numbers were congruent with their number-form. In contrast, the (...) controls exhibited a distance effect regardless of congruency or presentation type. The findings suggest that: number-form synesthesia impairs the ability to represent numbers in a flexible manner according to task demands; number-form synesthesia is a genuine tangible experience, triggered involuntarily; and the classic mental number line can be more pliable than previously thought and appears to be independent of cultural-lingo direction. (shrink)
Are small and large numbers represented similarly or differently on the mental number line? The size effect was used to argue that numbers are represented differently. However, recently it has been argued that the size effect is due to the comparison task and is not derived from the mental number line per se. Namely, it is due to the way that the mental number line is mapped onto the task-relevant output component. Here synesthesia was used to disentangle these two alternatives. (...) In two naming experiments a digit-color synesthete showed that the congruity effect was modulated by number size. These results support the existence of a mental number line with a vaguer numerical representation as numbers increase in size. In addition, the results show that in digit-color synesthesia, colors can evoke numerical representation automatically. (shrink)
It is widely agreed that irrelevant numerical values are automatically activated. However, automatic and intentional activations may give rise to different numerical representations. We examined processing of symbolic and non-symbolic representations asking whether they differ in automatic and intentional processing. Participants were presented with two-dimensional displays containing repetitions of a digit and were asked to report, in different blocks, whether the digit or numerosity was smaller or larger than 5. Incongruent trials differed either in laterality between the relevant and irrelevant (...) dimensions or in numerical distance between dimensions. Congruency affected performance regardless of symbolic or non-symbolic presentation. For incongruent trials, laterality affected performance, again regardless of presentation. This implies that automaticity does not mean similar processing of relevant and irrelevant dimensions. Specifically, the relevant dimension is processed elaborately whereas the irrelevant dimension is processed crudely. (shrink)
Simple specialization cannot account for brain functioning. Yet, we believe Anderson's reuse can be better explained by re-function. We suggest that functional demands shape brain changes and are the driving force behind reuse. For example, we suggest that the prefrontal cortex (PFC) is built as an infrastructure for multi-functions rather than as a module for reuse.
Number is known for influencing time processing, but to what extent time influences number in human adults is unclear. We investigated possible bidirectional interactions using a novel Stroop-like task; participants compared numbers or temporal durations in congruent or incongruent conditions . Time and number tasks were presented in different blocks or within the same block of trials with task instructions provided at the offset of the stimuli . Analyses of response times and their distribution revealed that number affected time from (...) early RTs, and time affected number at late RTs – an asymmetry observed only when time and number tasks were presented in separate blocks. Thus, carefully chosen tasks and appropriate data analysis can reveal bidirectionality between time and number, consistent with shared magnitude or decision mechanisms. (shrink)
Numbers are fundamental to our understanding of, and survival in, the environment. Not surprisingly, numbers represent an important psychological dimension in triggering synaesthetic experiences, such as in digit-colour synaesthesia, or number-space synaesthesia. Another important consideration is directionality in synaesthesia, in that we might ask whether the stimulus and response in any given synaesthetic variant can also work on the opposite way. Most studies have documented the typical direction of the synaesthetic experience from the inducer to the concurrent. However, it seems (...) that some synaesthetes do show bi-directionality, that is, their concurrent might also trigger the inducer either at an implicit level, or even at the explicit level that reaches perceptual awareness. We discuss these two issues in this book chapter. We will first explore synesthesia and automaticity where numbers are concerned, followed by a discussion on synaesthesia and directionality. (shrink)
We agree with Cramer et al. that pure cases of behavioral disorders with no symptom overlaps are rare. However, we argue that disorders do exist and the network idea is limited and limiting. Networks of symptoms are observed mainly at behavioral levels. The core deficit is commonly at the cognitive or brain levels, and there the story is completely different.
In this commentary we make two rejoinders to Jung & Haier (J&H). First, we highlight the response selection component in tasks as a confounding variable that may explain the parieto-frontal involvement in studies of human intelligence. Second, we suggest that efficient response selection may be an integral part of the definition of intelligence.