Name: visual masking with object substitution
Uploaded: 2023-04-30T06:50:35.000Z
Duration: 10 min 14 s
Channel: JoVE

K12 Standards

new-york-state-science-learning-standards

New York State Science Learning Standards

High School

Life Science

Structure and Function

HS-LS1-2.

Object Substitution Masking

1. 刺激材料与实验设计
<ol>
	<li>进行本实验时，您需要一个编程环境（例如 MATLAB）或实验序列软件（例如 E-Prime）。</li>
	<li>每次试验包含四个基本组成部分：一个注视点十字、一个形状刺激显示（称为目标显示）、一个掩蔽图像（四个点）以及一个反应显示。图1展示了每次试验中的四个主要元素。
	<ol>
		<li>显示背景始终为白色。</li>
		<li>注视点十字是一个位于屏幕中央的小十字，十字每臂长0.25 cm。除反应显示出现时外，注视点十字将始终可见。</li>
		<li>反应显示由一个黑色轮廓的正方形、圆形、菱形和三角形组成，水平排列于屏幕中央。每个形状均应内接于一个半径为0.75 cm的假想圆中。</li>
		<li>目标显示将包含八个形状，每次试验从以下四种黑色轮廓形状中随机选取：圆形、正方形、菱形和三角形。每次试验中不必包含所有形状，且形状可以（并且确实会）重复出现。同样，每个形状的半径均为0.75 cm，它们将随机出现在以屏幕中央注视点十字为中心、半径为1.5 cm的假想圆周上。</li>
		<li>掩蔽图像由四个半径为0.25 cm的黑色圆盘（点）组成，这些点应排列成一个正方形的四个角，其大小刚好足以将全部四个目标形状包含在内。</li>
	</ol>
	</li>
</ol>
<img alt="视觉感知测试示意图；认知研究中的注视、目标、掩蔽和反应显示。" src="/files/ftp_upload/10279/10279fig1.jpg" data-altupdatedat="1761830439000" data-alt="图1"> 
图1：物体替换显示的主要组成部分。 每次试验均以注视显示开始，参与者将被指示在启动试验前先注视十字。每次试验以反应显示结束，参与者需在四个圆点之间选择其记得看到的形状。在注视显示与反应显示之间，会出现一个目标显示，其中呈现八个形状组成的环，同时还会出现由四个圆点构成的掩蔽，位于其中一个形状周围的位置。如实验步骤中更详细所述，掩蔽和目标显示可以不同顺序出现，但每个显示持续时间为30 ms。
<ol start="3">
	<li>每次试验的事件序列均以一个注视屏幕开始，该屏幕将一直显示直至参与者按下空格键，并在按键后继续呈现200毫秒。</li>
	<li>一次试验将始终以一个反应显示结束，该显示将持续呈现，直到参与者做出反应（通过点击她认为在该次试验中四个点之间所看到的形状）。</li>
	<li>在注视点与反应显示之间，会依次呈现目标显示和掩蔽，每个持续30 ms。在每次试验中，掩蔽将围绕随机选择的目标形状的位置呈现。</li>
	<li>本实验中关键的自变量是刺激呈现异步性（stimulus onset asynchrony, SOA）。SOA定义为两个刺激起始时间之间的时间差，在本实验中即掩蔽刺激与目标刺激显示之间的起始时间差。因此，SOA等于目标刺激显示起始时间减去掩蔽刺激显示起始时间。 图2-4 用不同的SOA设计该实验的多个试验。
	<ol>
		<li>如果SOA为0，则意味着两个刺激同时呈现（并且由于每个刺激持续30 ms，它们也会同时消失）。</li>
		<li>如果SOA为负值，则表示掩蔽刺激先出现 之前 目标显示。</li>
		<li>如果SOA为正值，则表示掩蔽刺激先出现 之后 目标显示。</li>
		<li>该实验将包含15个不同的SOA，分别为0 ms，以及正负值：10、30、50、70、90、150和300 ms。</li>
	</ol>
	</li>
</ol>
<img alt="视觉搜索实验示意图；SOA=0ms，形状图案，持续时间30ms。" src="/files/ftp_upload/10279/10279fig2.jpg" data-altupdatedat="1761830439000" data-alt="图2"> 
图2：0毫秒的刺激呈现异步时间。 在SOA为0毫秒的试验中，掩蔽刺激与目标刺激同时出现。由于每个刺激均被设定为持续呈现30毫秒，因此它们也同时消失。
<img alt="视觉感知时序图；SOA=50ms 和 -50ms；图形排列；注意研究。" src="/files/ftp_upload/10279/10279fig3.jpg" data-altupdatedat="1761830439000" data-alt="图 3"> 
图 3：刺激起始非同步性为 50 ms。 无论 SOA 为负值或正值，50 ms 的 SOA 表示一个刺激比另一个刺激晚 50 ms 开始。但这些刺激被设定持续时间仅为 30 ms，这意味着 50 ms 的 SOA 将导致显示画面中有 20 ms 的空白期（仅保留注视十字）。在本实验中，我们将 SOA 定义为目标刺激起始至掩蔽刺激起始的时间差，因此负的 SOA 值表示掩蔽刺激先出现，正的 SOA 值表示掩蔽刺激后出现。
<img alt="视觉搜索任务示意图；刺激呈现异步性（SOA）条件、符号、时间安排、知觉研究。" src="/files/ftp_upload/10279/10279fig4.jpg" data-altupdatedat="1761830439000" data-alt="图 4"> 
图 4：10 毫秒的刺激呈现异步性（SOA）。 当掩蔽刺激和目标刺激均被编程为持续呈现 30 毫秒时，10 毫秒的 SOA 导致两者重叠呈现的时间为 20 毫秒。
<ol start="7">
	<li>实验程序应包含15种SOA条件中的每一种各20次试验，并将所有不同类型的试验随机混合。</li>
	<li>关键因素是参与者无法预知每轮试验中点的位置，因此必须确保点的出现位置在各次试验中具有不可预测性。</li>
	<li>确保实验程序输出足够的每轮试验信息，以便后续进行结果分析。每轮试验所需记录的相关信息包括：试验编号、该次试验的SOA、掩蔽刺激之间呈现的形状，以及参与者给出的形状判断反应。</li>
</ol>
2. 运行实验
<ol>
	<li>进行本实验时，需招募10名参与者，并在安静的房间内逐一进行测试。</li>
	<li>当参与者到达实验现场时，将其安置在距离测试计算机显示器60 cm的位置。</li>
	<li>屏幕上的图像应为包含目标和掩蔽的显示画面。使用此图像按以下方式说明实验指导：
	<ol>
		<li>在本实验的每一次试验中，您将看到一圈形状，如图中所示 [指向图像]。此外，您还会看到四个点，如这里的点所示。有时它们会重叠，如本图所示；但有时其中一个会先于另一个出现。无论它们出现的顺序如何，您的任务只是尝试看清并记住出现在这四个点之间的区域中的形状。这样说明是否清楚？</li>
		<li>很好。有时您可能会觉得任务较难，感觉完全不知道答案。在这种情况下，请随意猜测即可。还有几点需要注意：每次试验开始时，屏幕上仅显示一个十字，如中间所示。在开始每次试验前，请确保您正注视着十字，并尽量保持眼睛不动。当您准备就绪后，按下空格键以开始试验。</li>
	</ol>
	</li>
	<li>向参与者解释完指导语后，启动实验，并观察参与者完成四到五次试验，以确保其已理解指导语。随后让其独立完成剩余实验。</li>
</ol>
3. 分析结果
<ol>
	<li>为了分析结果，您首先需要针对每位被试和每个刺激呈现时间间隔（SOA）单独计算反应正确率。</li>
	<li>接下来，可以按 SOA 对不同被试的反应正确率进行平均。</li>
	<li>为了确定 SOA 对任务表现是否存在显著影响，可使用 MATLAB 或 SPSS 等统计软件，以正确率为因变量、SOA 为自变量进行重复测量方差分析（ANOVA）。</li>
</ol>

近年来，对象替换掩蔽的众多应用中包括一些研究，这些研究将其与神经生理学技术结合使用，以分离出参与意识体验产生的脑回路。Hirose 及其同事2 2005年，Hirose 等人开展了一项实验，采用了一种称为重复经颅磁刺激（rTMS）的技术：研究人员利用磁线圈在受试者大脑中诱导产生微小的电位，重复诱导可导致皮层的一小部分在短时间内失活。 等 研究中，他们失活了视觉皮层中一个名为 V5/MT+ 的区域，结果发现，在正性 SOA 条件下，点的呈现不再阻碍对刺激的感知。V5/MT+ 已知在运动感知中起重要作用。该研究表明，该区域的功能可能更为广泛，参与将感知体验中的各个瞬间联系在一起。当该区域功能被干扰时，掩蔽刺激与目标刺激无法被知觉为同一事件的一部分，因此掩蔽效应失效。 
对象替换掩蔽的另一种应用是研究刺激是否必须进入意识层面才能影响行为。例如，一个被掩蔽的词无法被观察者报告出来。然而，它是否仍会产生启动效应？一些研究表明，确实如此。3

客体替代掩蔽

来源：Jonathan Flombaum 实验室——约翰斯·霍普金斯大学
视觉掩蔽是感知科学家使用的一个术语，用来描述一系列现象，即一幅图像被呈现出来，但由于第二幅图像的出现，观察者无法感知到该图像。掩蔽有多种不同类型，其中许多相对直观且不出人意料。但有一种令人意外且重要的掩蔽类型被称为客体替代掩蔽。自1997年左右由Enns和Di Lollo相对近期地发现以来，它一直是视觉科学研究的重点。1
本视频将演示如何进行客体替代实验的标准操作步骤、如何分析实验结果，并解释这种特殊形式掩蔽现象的假设成因。

图5展示了参与者在不同SOA条件下的平均反应正确率。从图中可以明显看出，对这些结果进行方差分析（ANOVA）可能会显示出SOA的显著效应。这种效应具体表现为：在SOA绝对值较大（无论是正值还是负值）时，掩蔽刺激几乎不起作用，任务表现非常好。当掩蔽刺激与目标刺激相隔150或300毫秒时，两者实际上已成为独立的事件。但这些条件尤为关键，因为它们表明，即使目标图形仅呈现30毫秒，也能够被感知，并与四个点的位置建立关联。换句话说，这些结果说明呈现时间本身并非本质上过短而无法被感知。同样，在负SOA条件下，表现也普遍较好。这些试验中，掩蔽刺激出现在目标刺激之前。即使在SOA为-10和0的条件下，表现仍达到50%或更高，且在此类SOA条件下，掩蔽刺激与目标刺激的重叠时间为20至30毫秒。
<img alt="客体替代掩蔽效应图；正确率 vs SOA（毫秒），表示知觉限制。" src="/files/ftp_upload/...

来源：约翰·霍普金斯大学 Jonathan Flombaum 实验室  
视觉掩蔽是感知科学家用来指代一系列广泛现象的术语，用于描述一种视觉刺激的感知因另一刺激的呈现而受到干扰或抑制的情况。

视觉世界充满了在空间和时间上相互作用的物体，而这些维度上的重叠可能会影响人们对它们的意识感知，这一概念被称为视觉掩蔽。类似于有人穿着伪装服装，当一个目标物体（例如一张面孔）由于第二个物体（即掩蔽物）的存在而无法被感知时，就会发生这种现象。当目标被一个在部分相同空间位置上重叠的刺激所替代时，这种现象称为客体替代，是一种视觉掩蔽形式。基于 Enns 和 Di Lollo 于 1997 年开创的方法，本视频演示了如何设计和实施客体替代掩蔽实验，以及如何分析数据并解释与形状意识感知相关的结果。在本实验中，当参与者观察计算机屏幕上呈现的四个元素时，会诱导产生客体替代掩蔽效应，这四个元素分别为：注视十字、目标显示、掩蔽刺激和反应选项。每次试验开始时，屏幕上会显示一个由位于屏幕中央的50毫米线条组成的注视十字，以确保参与者集中注意力。接着是第二个元素，即目标显示：从四种图像（圆形、正方形、菱形和三角形）中随机选出的八个形状。这些形状在半径为150 mm的隐形圆形周围显示30 ms。紧随其后的是第三个元素，即掩模，由四个黑色圆点组成，每个圆点的半径为 25 mm，排列成一个正方形的四个角，该正方形的尺寸恰好足以包围一个图形。该掩模围绕随机选定的目标图形位置呈现，并在每次试验中持续显示 30 ms。此处一个关键的自变量是刺激起始异步性（简称 SOA），定义为目标显示与掩蔽刺激出现之间的时间差。正的刺激呈现异步时间意味着掩蔽刺激将在目标刺激之后出现。例如，当SOA为50 ms时，目标刺激显示30 ms，随后仅有注视十字呈现20 ms，然后掩蔽刺激再呈现30 ms。当SOA小于30 ms时，例如10 ms，目标显示在掩蔽刺激可见之前先呈现10 ms。再经过20 ms后，目标显示消失，而掩蔽刺激继续保留10 ms。目标显示和掩蔽同时出现在屏幕上的时间称为刺激重叠。当刺激起始不同步性为零时，刺激重叠达到最大。当刺激呈现异步时间为负值时，元素的呈现顺序会反转：掩蔽刺激在目标显示之前出现。在SOA为-10 ms时，掩蔽刺激先呈现10 ms，随后目标刺激重叠呈现20 ms。之后掩蔽刺激消失，仅留下目标显示再持续可见10 ms。当负值较大时，例如 SOA 为 -50 ms，掩蔽刺激呈现 30 ms，随后有 20 ms 的时间仅呈现注视十字，之后目标刺激显示 30 ms。无论SOA如何，第四个也是最后一个元素是反应显示：屏幕中央水平排列的四个形状。这些形状会一直显示，直到参与者按下与其所选形状对应的按键为止。因变量是记录在不同刺激呈现间隔（SOA）下的正确反应百分比。预期在特定的时间范围内会出现客体替代掩蔽效应，即当掩蔽刺激在目标刺激呈现后不久出现并与其显示重叠时，被试在正SOA条件下的任务表现准确率会下降。实验开始时，在实验室中向其中一位招募的受试者致意，并指导其完成知情同意书的签署。随后，让受试者舒适地坐在测试计算机显示器前方60 cm处。解释任务说明：参与者将看到一个由八个形状组成的环，以及四个随机位置出现的点。需说明该掩蔽刺激有时可能在时间上与某个形状重叠，但也可能先于或后于该形状出现。指导参与者记住出现在中间区域的形状，当不确定时，只需进行猜测。理解主要规则后，再说明几个要点：受试者应在每次试验开始时按下空格键；当屏幕上出现注视十字时，在试验过程中不得移动眼睛。现在，让参与者启动程序并观察他们完成若干次试验。此时，离开房间。在无监督的情况下，让参与者完成全部300次试验，每个刺激呈现异步值对应20次试验。注意共有15个值，范围从负值（掩蔽刺激先于目标刺激）到正值（掩蔽刺激后于目标刺激），包括一个重叠区域。当参与者完成任务后，返回房间并感谢他们参与本次实验。为分析数据，需计算所有刺激呈现异步时间点的反应准确率（以正确率百分比表示），并绘制15个时间点的平均值图表。正如所预测的，当SOA非常大（正或负的150或300 ms）时，被试的表现非常准确，因为掩蔽刺激和目标刺激的呈现被感知为两个独立的事件。同样，对于 -90 至 -10 毫秒之间的负性SOA，由于在目标显示出现之前掩蔽刺激已引导参与者将注意力指向正确位置，因此其表现相当准确。然而，当刺激间隔时间接近零时，由于刺激重叠且呈现时间过短而无法被感知，准确率下降至50%。 SOA的关键范围为10至90之间的数值，此期间目标显示出现在掩蔽刺激之前。在此范围内，被试的表现较差，接近随机水平。这表明发生了客体替代掩蔽，且四点掩蔽刺激足以在形状形成意识感知之前干扰大脑的处理。现在您已经熟悉了客体替代掩蔽，接下来让我们探讨它在意识觉察研究中的应用，以及在视觉感知神经回路研究中的使用。这种掩蔽范式可与重复经颅磁刺激（rTMS）结合使用，以分离参与意识感知的脑回路。通过使用磁线圈在脑内反复诱导产生微小的电位，从而使一小部分皮层短暂失活。在一项研究中，Hirose 及其同事发现，如果在任务过程中使视觉皮层中与运动感知相关的 V5/MT+ 区域失活，则能够消除掩蔽效应的影响。这表明，rTMS 干扰导致掩蔽刺激与目标刺激不再被感知为同一事件的一部分，从而使受试者能够同时看到两者。其他研究人员正在探究某种刺激是否必须被感知才能影响行为，例如言语启动效应。有关此效应的更多细节，请查看我们认知心理学合集中的视频《言语启动》。在Goodhew及其同事进行的一项研究中，他们采用了一种掩蔽任务的变体——掩蔽中的四个点为粉色或蓝色——并要求参与者记住颜色。掩蔽刺激与目标刺激同时呈现，目标刺激包括单词PINK、BLUE、MAIL、HOUR、JQCG和AWHF。当刺激呈现间隔（SOA）为200毫秒时，若目标词是颜色名称，参与者对掩蔽刺激颜色的命名速度比目标词不是颜色名称时更快。无论参与者能否正确判断目标是单词还是非单词，这一现象均存在，表明刺激即使未被察觉或未进入意识，仍可发挥作用。您刚刚观看了 JoVE 关于客体替代掩蔽的视频。现在，您应该已经很好地掌握了如何设计实验元素、实施实验，以及如何分析和评估实验结果。感谢观看！

Education

教育

JoVE Science Education

Psychology

心理学

Sensation and Perception

感觉与知觉

对象替换掩蔽

visual masking with object substitution

Visual masking describes cases where one image is presented, but an observer does not perceive it because a second image appears. In vision science, this kind of interference helps researchers study how the brain selects and stores visual information.

Object substitution masking is a surprising form of visual masking. It became an important topic in vision research after it was discovered relatively recently, around 1997, by Enns and Di Lollo. The effect has been studied because it shows that a visible object can be missed even when the scene seems simple.

This page explains standard object substitution experiments and how the results are analyzed. It also describes the hypothesized causes of this unusual masking effect. The methods shown here help clarify why some images are seen and others are not.

Visual Masking with Object Substitution

color afterimages

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Peripheral Vision and Letter Crowding

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Psychophysics studies how physical changes become neural signals and mental ideas about magnitude. A key idea in this field is the just-noticeable difference, or JND. A JND is the smallest change people can perceive. Size is a clear way to study JND. Small changes in a child’s height may go unnoticed from day to day. After a longer absence, such as a return from sleep-away camp or a visit after many weeks, those same small changes can seem obvious because they have added up. Researchers...

the staircase procedure for finding a perceptual threshold

the-staircase-procedure-for-finding-a-perceptual-threshold

Measuring Auditory Thresholds with Staircase Testing

Psychophysics studies how the physical strength of a stimulus relates to what people actually perceive. It focuses on perceptual thresholds, which are the smallest amounts of stimulation a person can sense. Examples include the brightness needed to see a light, the pressure needed to feel touch, and the softness of a sound that can still be heard. The staircase procedure is an efficient method for finding a perceptual threshold. Here, the stimulus is adjusted step by step based on a person’s...

object substitution masking

Visual masking describes cases where one image is presented, but an observer does not perceive it because a second image appears. In vision science, this kind of interference helps researchers study how the brain selects and stores visual information. Object substitution masking is a surprising form of visual masking. It became an important topic in vision research after it was discovered relatively recently, around 1997, by Enns and Di Lollo. The effect has been studied because it shows that...

sensation and perception

这本文集探讨了各种程序, 研究如何大脑处理我们复杂的感官世界, 解决问题的意识意识和视觉, 触觉, 和听觉感知。

Explore visual masking and object substitution masking in high school-friendly terms. Learn how researchers test perception, analyze results, and study why some images go unseen.

Visual Masking with Object Substitution | JoVE K12

Jonathan Flombaum

Overview

Experimental Design

Running the Experiment

Representative Results

Applications

Summary

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Visual Masking with Object Substitution

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