Can Crossover and Altered Magnitude Estimation in Neglect Be Explained by Contextual Effects?
Can Crossover and Altered Magnitude Estimation in Neglect Be Explained by Contextual Effects?
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2022
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进行了三项使用刺激情境的实验操作和相关分析的研究，以研究情境效应如何影响幅度估计和线平分的交叉效应。先前的研究表明，虽然在二等分之前将注意力集中到线的一端决定了交叉发生的方向，但幅度估计中的偏差实际上会产生交叉效应。然而，在这些先前的交叉模型中没有研究上下文效应对震级估计的影响。因此，本次调查的目的是检验这些影响。当前研究的对象是健康对照者和因中风而左右半球损伤的人，无论有没有空间忽视。研究 1 检查了有或没有刺激背景的平分线的交叉效应。研究 2 检查了刺激顺序和响应顺序背景对震级估计的影响。研究 3 研究了刺激情境效应对震级估计的方差有多大，以及刺激情境如何影响交叉效应。结果表明，情境偏差普遍存在，但在正常受试者的大小估计中相对较小。在因中风而导致右半球或左半球损伤的受试者中，情境偏差被夸大到类似程度，但情境偏差所造成的方差量仍然相当小。研究 2 的一个新发现是，在单侧脑损伤的受试者中，先前对刺激的反应以及先前刺激的强度可以诱发情境效应。这可能是与反应持续相关的情境效应。最后，研究 1 和 3 表明，上下文效应增强了线平分的交叉效应，主要是在相对较短的线上。然而，情境效应不能完全解释交叉效应，因为在没有刺激情境的情况下也观察到交叉二分。结论是交叉效应可以通过注意力方向和幅度估计的偏差来解释。上下文效应是震级估计中的偏差来源之一，它通过促进短线长度（<2 cm）上的对侧误差来影响交叉效应。
Three studies that used experimental manipulations of stimulus context and correlational analyses were conducted to examine how contextual effects influence magnitude estimation and the crossover effect on line bisection. Previous work had shown that although orienting attention to one end of a line prior to bisection determines the direction in which crossover occurs, bias in magnitude estimation actually produces the crossover effect. The influence of contextual effects on magnitude estimation, however, was not examined in these previous models of crossover. Consequently, the purpose of the present investigation was to examine these effects. Subjects in the current studies were healthy controls and people who had right and left hemisphere injury due to stroke, both with and without spatial neglect. Study 1 examined the crossover effect for lines bisected with and without a stimulus context. Study 2 examined both stimulus order as well as response order context effects on magnitude estimation. Study 3 examined how much variance in magnitude estimation was accounted for by stimulus contextual effects and how stimulus context influenced the crossover effect. The results showed that contextual bias was ubiquitous but relatively small in the magnitude estimates of normal subjects. Contextual bias was exaggerated to a similar degree in subjects with right or left hemisphere injury due to stroke, but the amount of variance accounted by contextual bias was still quite small. A novel finding of study 2 was that contextual effects can be induced by previous responses to stimuli as well as by the magnitude of preceding stimuli in subjects with unilateral brain injury. This may be a contextual effect related to response perseveration. Finally, studies 1 and 3 indicated that contextual effects strengthened the crossover effect on line bisection, primarily on relatively short lines. Contextual effects, however, cannot fully account for the crossover effect, because crossover bisections were observed also in the absence of a stimulus context. It is concluded that the crossover effect is explained by biases in attentional orientation and magnitude estimation. Contextual effects represent one source of bias in magnitude estimation that influences the crossover effect by promoting contralateral errors on short line lengths (<2 cm).