Hubbard Edward M, Ranzini Mariagrazia, Piazza Manuela, Dehaene Stanislas
INSERM-CEA Cognitive Neuroimaging Unit, CEA/SAC/DSV/I2BM/NeuroSpin, Gif-Sur-Yvette, France.
Cortex. 2009 Nov-Dec;45(10):1200-16. doi: 10.1016/j.cortex.2009.06.011. Epub 2009 Jul 7.
Numerous behavioural paradigms have demonstrated a close connection between numbers and space, suggesting that numbers may be represented on an internal mental number line. For example, in the Spatial Numerical Association of Response Codes (SNARC) effect, reaction times are faster for left-sided responses to smaller numbers and for right-sided responses to larger numbers. One valuable tool for exploring such numerical-spatial interactions is the study of number-form synaesthesia, in which participants report vivid, automatic associations of numerical and other ordinal sequences with precise, idiosyncratic, spatial layouts. Recent studies have demonstrated the influence of synaesthetic spatial experiences on behavioural number tasks. The aim of the present study is to further explore these internal spatial representations by presenting a case-study of an unusual synaesthete, DG, who reports highly detailed representations not only of numerical sequences (including representations of negative and Roman numbers), but also different representations for other ordinal sequences, such as time sequences (months, days and hours), the alphabet, financial sequences and different units of measure (e.g., kilograms, kilometres and degrees). Here, we describe DG's synaesthetic experiences and a series of behavioural experiments on numerical tasks concerning the automaticity of this phenomenon. DG's performance on number comparison and cued-detection tasks was modulated by his synaesthetic mental representation for the numerical sequence, such that his reaction times were slower when the spatial layout was incompatible with the orientation of his mental number line. We found that the spatial presentation of stimuli, rather than the implicit or explicit access to numerosity required by tasks, was essential to eliciting DG's number-forms. These results are consistent with previous studies and suggest that numerical-spatial interactions may be most strongly present in synaesthetes when both numerical and spatial information are explicitly task-relevant, consistent with a growing body of literature regarding the SNARC and other related effects.
众多行为范式已证明数字与空间之间存在紧密联系，这表明数字可能在内部心理数字线上得到表征。例如，在反应编码的空间数字关联（SNARC）效应中，对较小数字的左侧反应以及对较大数字的右侧反应的反应时间更快。探索这种数字 - 空间相互作用的一个有价值的工具是对数 - 形联觉的研究，在这种研究中，参与者报告数字和其他序数序列与精确、独特的空间布局之间生动、自动的关联。最近的研究已经证明了联觉空间体验对数字行为任务的影响。本研究的目的是通过呈现一个不寻常的联觉者DG的案例研究来进一步探索这些内部空间表征，DG不仅报告了高度详细的数字序列表征（包括负数和罗马数字的表征），还报告了其他序数序列的不同表征，如时间序列（月、日和小时）、字母表、财务序列以及不同的度量单位（例如，千克、千米和度）。在这里，我们描述了DG的联觉体验以及一系列关于数字任务的行为实验，这些实验涉及这种现象的自动性。DG在数字比较和线索检测任务上的表现受到他对数字序列的联觉心理表征的调节，以至于当空间布局与他的心理数字线方向不兼容时，他的反应时间会变慢。我们发现刺激的空间呈现，而不是任务所需的对数量的隐式或显式访问，对于引发DG的数字形式至关重要。这些结果与先前的研究一致，并表明当数字和空间信息都与任务明确相关时，数字 - 空间相互作用可能在联觉者中最为强烈，这与关于SNARC和其他相关效应的越来越多的文献一致。
