Name: measuring size changes with jnd
Uploaded: 2023-04-30T06:47:31.000Z
Duration: 7 min 30 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.

Just-noticeable Differences

1. 仪器设备
<ol>
	<li>本实验需使用计算机及实验实施软件（如 E-Prime），或编程环境（如 MATLAB 或 PsychoPy）。</li>
</ol>
2. 刺激材料与实验设计
<ol>
	<li>本实验将采用相同的基本设计进行多次重复试验。屏幕上会同时出现两个圆盘，一个位于左侧，另一个位于右侧。其中一个始终比另一个大，任务是通过按键选择较大的那个。具体细节如下：</li>
	<li>编程使实验绘制一个半径为 10 px 的蓝色圆盘。该圆盘将在每次试验中出现，垂直方向居中显示，水平方向则居于屏幕左半部分或右半部分的中心。这种在每次试验中保持不变的刺激有时被称为恒定刺激法。这仅表示每轮试验中的两个刺激之一始终相同。因此，该 10 px 的蓝色圆盘即为恒定刺激。</li>
	<li>在每轮试验中，与恒定刺激相对的位置显示另一个蓝色圆盘。该圆盘称为比较刺激。其半径在 5 至 9 px 和 11 至 15 px 之间，共 10 种可能取值。在实验中，每种可能的比较刺激各进行 10 次试验。因此，整个实验共包含 200 次试验。</li>
	<li>将两个刺激在屏幕上显示 200 ms，随后显示仅包含“哪个更大？L/R？”的屏幕。图 1 示意了每轮试验中的事件序列。
	<ol>
		<li>按“L”键表示左侧物体更大，按“R”键表示右侧物体被感知为更大。</li>
	</ol>
	</li>
	<li>确保程序将以下重要数据输出至表格中：试验编号、比较刺激的大小、比较刺激的屏幕位置、正确答案以及参与者给出的反应。图 2 展示了此类数据表的一个示例。</li>
</ol>
<img alt="心理实验示意图；圆形大小的视觉比较方法；注意力测量。" src="/files/ftp_upload/10229/10229fig1.jpg" data-altupdatedat="1761830439000" data-alt="图1"> 
图1. 测量圆大小的最小可觉差（JND）实验中单次强制选择试验的示意图。 首先，准备界面提示参与者试验即将开始。随后，两个蓝色圆盘并排出现在屏幕上，持续显示仅200 ms，随后界面提示参与者做出反应。“L”键用于表示左侧物体，“R”键用于表示右侧物体。
<img alt="显示大小、位置和反应评估的试验比较数据表。" src="/files/ftp_upload/10229/10229fig2.jpg" data-altupdatedat="1761830439000" data-alt="图 2"> 
图 2. 强迫选择 JND 实验的一个示例输出表格。 各列报告了实验程序中的相关数据。
3. 运行实验
<ol>
	<li>招募一名受试者，当她到达实验室时，告知她将参与一项关于形状知觉的简单实验，然后让她签署知情同意书。</li>
	<li>让受试者坐在测试计算机前，并按如下方式说明任务内容：
	<ol>
		<li>本实验的每一次试验都包含相同的基本流程。首先，你会在屏幕上看到“Ready?”字样。当你准备开始试验时，请按下空格键。随后，屏幕两侧会非常短暂地出现两个蓝色圆盘。当它们消失后，屏幕上将显示“Which was bigger, L/R?”（哪一个看起来更大，左边还是右边？）。你的任务是报告你认为哪个圆盘看起来更大，是屏幕右侧的还是左侧的。本实验共有200次试验，但每次都很短暂，整个实验应在五分钟内完成。你有任何问题吗？</li>
	</ol>
	</li>
	<li>回答完任何问题后，启动实验程序，让受试者开始实验。让她独自留在安静的测试房间内，直至实验结束。</li>
</ol>
4. 分析结果
<ol>
	<li>分析结果时，首先要确定哪些反应是正确的，哪些是错误的。为此，在数据输出表中添加一列，将给出的反应与正确反应进行比较，若反应正确，则在该列中标记为 1，若不正确，则标记为 0。
	<ol>
		<li>快速检查以确保表现合理——当比较对象为 5 和 15 像素时，参与者应达到或接近完全准确，因为与 10 相比差异足够大，不应出现错误。</li>
	</ol>
	</li>
	<li>现在在数据表中再添加一列，命名为“选择比较对象的比例（Proportion of C Responses）”。在该列中记录参与者选择的是比较对象还是恒定对象。如果选择了比较对象，则在该列中标记为 1；如果选择了恒定对象，则标记为 0。</li>
	<li>接下来，针对每个比较对象的大小，计算参与者选择其为较大对象的频率比例。对于大小为 5 的比较刺激，该数值应接近 0；而对于大小为 15 的比较刺激，该数值应接近 1。</li>
	<li>为了直观展示结果，按以下方式绘制图形：创建散点图，横轴（x 轴）表示比较对象的大小，纵轴（y 轴）表示其被选择的比例。图形将类似于图 3所示。</li>
</ol>
<img alt="尺寸与反应比较图；逻辑曲线；数据分析；统计图；半径像素。" src="/files/ftp_upload/10229/10229fig3.jpg" data-altupdatedat="1761830439000" data-alt="图3"> 
图3. 通过强迫选择实验测定圆半径的差别阈限（JND）的结果。 图中绘制的是被试选择比较刺激更大时所占的比例，作为比较刺激尺寸的函数。标准刺激的半径始终保持为10 px。

恒定刺激法在测量最小可觉差（JND）方面的一个主要应用出现在神经科学领域，特别是用于研究单个神经元的放电如何编码外界物理特性的神经生理学实验。这类研究通常涉及在猴子的视觉皮层植入电极。电极穿透单个细胞，这些细胞通过放电或称“峰电位”（即传递快速的电信号）对视觉刺激产生反应。在采用JND方法的研究中，研究人员发现单个神经元具有噪声特性——它们对刺激的大小、亮度或颜色每次的反应大致相同，但存在一定变异性。其结果是，两个非常相似的刺激有时会引发相同的神经反应。例如，半径为10像素的圆有时会引发与半径为9像素或11像素的圆相同的神经元反应。这正是JND被称为“刚刚可察觉”的原因：在某些情况下，大脑中相关刺激确实会产生无法区分的效应。

可察觉差异阈值

来源：Jonathan Flombaum 实验室——约翰斯·霍普金斯大学
心理物理学是心理学和神经科学的一个分支，旨在解释物理量如何转化为神经元的放电活动以及对强度的心理表征。该领域关注的一类问题涉及最小可觉差（JND）：一个刺激需要改变多少，这种变化才能被察觉？为了帮助理解这一概念，可以考虑这样一个事实：相对而言，幼儿的生长速度非常快，但人们却很少能察觉到其每日的细微变化。然而，当孩子从离家的夏令营归来，或祖父母在长时间未见后再次见到孩子时，仅仅几周的生长变化就变得非常明显，甚至可能显得极为显著！身高的变化只有在经过一段时间的分离后才会被注意到，这是因为日常发生的微小变化太小，无法被感知。但在长时间未见之后，许多微小的变化累积起来就足以被察觉。那么，究竟需要发生多大的变化才能被注意到呢？这个最小的量就是最小可觉差（JND）。
心理学家和神经科学家在多个领域中测量最小可觉差（JND）。光需要亮多少才能被察觉？声音需要大多少才能被注意到？他们通常采用强迫选择范式来获取这些测量数据。本视频将聚焦于物体尺寸，演示当形状面积发生变化时，测量最小可觉差（JND）的标准方法。

图3中的曲线显示了比较刺激被选择的时间比例随其半径大小变化的情况。请注意，在本实验中，标准刺激的半径始终为10像素。因此，当比较刺激的半径为5或6像素时，它几乎从不被选择；而当半径为14或15像素时，它几乎总是被选择。然而，当半径为9或11像素时，比较变得困难，参与者常常出错。差别阈限（JND）定义如下：比较刺激在约75%的试验中被选择时的尺寸，减去其在25%的试验中被选择时的尺寸，再除以2。此处这两个数值分别为12和8，因此圆半径的差别阈限为2像素。
之所以这样精确计算最小可觉差（JND），其背后存在复杂的数学原因，涉及统计学和正态分布（钟形曲线）的性质。但通过观察图形可使该计算过程更直观。当半径比10像素仅小或大1像素时，受试者出现大量错误，其表现接近0.5，这相当于完全凭猜测作出判断。但当像素差异达到2时，表现迅速变得更为准确；当像素差异为3或更大时，表现几乎达到完美。图4是<s...

来源：Jonathan Flombaum 实验室——约翰斯·霍普金斯大学  
心理物理学是心理学和神经科学的一个分支，旨在解释……

某物需要发生多大程度的变化才能被察觉到差异？试想一下快速成长的幼儿，他们几乎每天都在长高。然而，这些细微的变化往往难以察觉，尤其是当他们仍然够不到篮球筐的时候。在更长的时间范围内，他们的生长突增变得非常明显；事实上，增长的幅度可能看起来非常巨大！这些身高上的变化只有在经过一段时间后才会被注意到，因为每天微小的差异太小而无法察觉。最小但可感知的量称为最小可觉差，就此例而言，即为能够察觉到的最小生长量。本视频展示了一种测量形状大小的最小可觉差的标准方法。我们不仅讨论了设计和实施实验所需的各个步骤，还解释了如何分析数据并解读结果，以说明在面积上需要发生多小的变化才能被人眼察觉。在本实验中，向参与者短暂呈现两个大小不同的圆，并要求其判断哪一个更大。每次试验中，其中一个圆的周长始终保持不变，而另一个圆的周长则进行变化。这种方法被称为恒定刺激法。在此情况下，固定刺激被设计为半径10 px，并随机出现在屏幕左侧或右侧。相比之下，另一个称为比较刺激的圆，其半径将在5至9 px以及11至15 px之间变化。在这10种可能的情况下，比较刺激在每一侧各呈现10次，总共进行200次试验。因变量记录为被试选择哪个刺激为较大的那个。如果参与者感知到两个刺激在大小上存在差异，则预期其会选择正确。然而，当两个形状的周长较为接近且低于最小可觉差时，其表现预计会下降。实验开始时，在实验室中向参与者打招呼。让他们舒适地坐在计算机前，然后说明任务指示：屏幕上将显示“Ready?”字样，直到他们按下空格键为止。观察两个蓝色刺激出现，并指示参与者通过按“L”键（表示左侧）或“R”键（表示右侧）来判断他们认为哪个刺激更大。提醒他们，如果无法确定哪个更大，也应进行猜测。回答完参与者可能提出的任何问题后，离开房间。让参与者在5分钟内完成全部200次试验。当他们完成后，返回房间并感谢他们参与本次实验。为了分析数据，首先调取记录每位参与者反应的程序化输出文件。快速浏览数据，以确保实验表现合理——即当比较刺激的大小为 5 和 15 px 时，准确率接近完美。接下来，在输出表格中添加一列，命名为“Accuracy”，用于判断记录的答案是否正确。将所有试验中给出的答案与正确答案进行比较。使用以下 IF 语句，在答案正确时记录为 1，错误时记录为 0。现在，在表格中添加另一列，命名为“比较响应比例”。将“比较位置”列与“响应”列进行比较，并使用一个新的 IF 语句，当选择比较刺激时标记为“1”，若选择的是恒定圆圈则标记为“0”。为了可视化结果，绘制一个散点图，以比较刺激的大小为横轴（x轴），以被选择为较大的比例为纵轴（y轴）。请注意，标准刺激的半径始终为10像素，因此半径为5或6像素的刺激几乎从未被选中，而半径为14或15像素的刺激则总是被选中。当半径为9或11像素时，比较变得更加困难，参与者经常出错。事实上，表现处于随机水平，表明差异未被感知。为了计算最小可觉差，取被选择75%时间的比较尺寸（在此情况下为半径12），减去被选择25%时间的比较尺寸（半径8），然后将结果除以2，得到答案为2 px。换句话说，圆的半径至少需要相差 2 px，其大小才能被准确感知。现在您已经熟悉了视觉物体大小感知中的最小可觉差，接下来让我们探讨这种范式在神经生理学研究中的应用，以揭示大脑如何做出反应，以及在其他行为情境中的应用，例如区分食物中的脂肪含量水平。研究人员已探究视觉皮层中的单个神经元如何编码外界物体的物理特性，例如物体的大小。通过结合刺激呈现与测量放电模式的电生理记录技术，研究人员发现，对大小敏感的神经元有时会对实际大小不同的物体产生相同的反应。这就是为什么JND是刚刚能被察觉的：有时，在大脑中，相关刺激确实会产生无法区分的效应。此外，研究人员已采用最小可觉差任务来表征个体对食物中脂肪浓度的检测阈值。他们发现，体重指数较高的个体在尝到样品中脂肪酸之前，需要更高的可察觉差异（即更高的阈值）。这些结果可能为限制过量脂肪摄入提供新的方法。您刚刚观看了 JoVE 关于最小可觉差的简介。现在，您应该已经很好地理解了如何设计和运行该实验，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

只是明显的差异

measuring size changes with jnd

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 measure JNDs in many areas. They ask how much brighter a light must be to notice, or how much louder a sound must be. They often use a forced-choice paradigm, which means people must choose between options. This lesson focuses on size and shows a standard method for measuring a JND when the area of a shape changes.

Measuring Size Changes with JND

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just-noticeable differences

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...

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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 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...

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 just-noticeable differences in psychophysics and see how scientists measure the smallest size change people can detect using a forced-choice task.

Measuring Size Changes with JND | JoVE K12

Jonathan Flombaum

Overview

Stimulus and Experimental Design

Running the Experiment

Data Analysis and Representative Results

Applications

Summary

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10647.jpg

Cell Structure

Background
Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, ...

Visualizing Onion and Cheek Cells
ExpandImmediately before the experiment, wash and peel onion bulbs for the class.
Remove the entire brown outer skin and ...

Visualizing Onion and Human Cells
ExpandIn this experiment you will prepare different types of cells from a plant and animal, onion and human ...

What are Cells?

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

Cytoplasm

The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression ...

The Central Dogma

The DNA Helix

Nucleic Acids

DNA as a Genetic Template

Structure of a Gene

A gene is the fundamental unit of heredity. Every individual has two copies of each gene, one inherited from each parent. Although most people contain the ...

Chromosome Structure

Base-pairing and DNA Repair

What is Gene Expression?

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is comprised&#160; of nucleotides and proteins are ...

RNA Structure

The basic structure of RNA consists of a string of ribonucleotides attached by phosphodiester bonds. Although most RNA is single-stranded, it can form ...

Types of RNA

Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse ...

Transcription

Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Translation

Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes ...

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Protein and Protein Structures

Proteins: From Genes to Degradation

From DNA to Protein

The flow of genetic information in cells from DNA to mRNA to protein is described by the central dogma, which states that genes specify the sequence of ...

Protein Folding

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to ...

An Overview of Gene Expression

Gene expression is the complex process where a cell uses its genetic information to make functional products. This process is regulated at multiple ...

an-introduction-to-caenorhabditis-elegans

An Introduction to Caenorhabditis elegans

Caenorhabditis elegans is a microscopic, soil-dwelling roundworm that has been powerfully used as a model organism since the early 1970&rsquo;s.  It was ...

An Overview of Genetic Analysis

An organism&#8217;s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its ...

An Introduction to Cell Death

Necrosis, apoptosis, and autophagic cell death are all manners in which cells can die, and these mechanisms can be induced by different stimuli, such as ...

An Overview of Genetic Engineering

Genetic engineering &#8211; the process of purposefully altering an organism&#8217;s DNA &#8211; has been used to create powerful research tools and model ...

An Introduction to Cell Division

Cell division is the process by which a parent cell divides and gives rise to two or more daughter cells. It is a means of reproduction for single-cell ...

An Overview of Genetics and Disease

Many human diseases are associated with mutations or variations in genetic sequences. Some of these genetic variants are heritable, passed down from ...

an-introduction-to-cellular-and-molecular-neuroscience

An Introduction to Cellular and Molecular Neuroscience

Cellular and molecular neuroscience is one of the newest and fastest growing subdisciplines in neuroscience. By investigating the influences of genes, ...

Annexin V and Propidium Iodide Labeling

Staining with annexin V and propidium iodide (PI) provides researchers with a way to identify different types of cell death&#8212;either necrosis or ...

an-introduction-to-developmental-genetics

An Introduction to Developmental Genetics

Development is the complex process through which a single-celled embryo transforms into a multicellular organism. Developmental processes are guided by ...

Bacterial Transformation: Electroporation

The term &#x201C;transformation&#x201D; refers cellular ingestion of foreign DNA.  In nature, transformation can occur in certain types of bacteria.  In ...

an-introduction-to-molecular-developmental-biology

An Introduction to Molecular Developmental Biology

Molecular signals play a major role in the complex processes occurring during embryonic development. These signals regulate activities such as cell ...

bacterial-transformation-the-heat-shock-method

Bacterial Transformation: The Heat Shock Method

Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of ...

an-introduction-to-saccharomyces-cerevisiae

An Introduction to Saccharomyces cerevisiae

Saccharomyces cerevisiae (commonly known as baker&rsquo;s yeast) is a single-celled eukaryote that is frequently used in scientific research.  S. ...

Cell Cycle Analysis

Cell cycle refers to the set of events through which a cell grows, replicates its genome, and ultimately divides into two daughter cells through the ...

An Introduction to Transfection

Transfection is the process of inserting genetic material, such as DNA and double stranded RNA, into mammalian cells. The insertion of DNA into a cell ...

Chromatin Immunoprecipitation

Histones are proteins that help organize DNA in eukaryotic nuclei by serving as &#8220;scaffolds&#8221; around which DNA can be wrapped, forming a complex ...

An Overview of Epigenetics

Since the early days of genetics research, scientists have noted certain heritable phenotypic differences that are not due to differences in the ...

community-dna-extraction-from-bacterial-colonies

Community DNA Extraction from Bacterial Colonies

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
Traditional methods of analysis ...

Cytogenetics

Cytogenetics is the field of study devoted to chromosomes, and involves the direct observation of a cell&#8217;s chromosomal number and structure, ...

embryonic-stem-cell-culture-and-differentiation

Embryonic Stem Cell Culture and Differentiation

Culturing embryonic stem (ES) cells requires conditions that maintain these cells in an undifferentiated state to preserve their capacity for self-renewal ...

DNA Gel Electrophoresis

DNA gel electrophoresis is a technique used for the detection and separation of DNA molecules. An electric field is applied to a gel matrix comprised of ...

Enzyme Assays and Kinetics

Enzyme kinetics describes the catalytic effects of enzymes, which are biomolecules that facilitate chemical reactions necessary for living organisms. ...

DNA Ligation Reactions

In molecular biology, ligation refers to the joining of two DNA fragments through the formation of a phosphodiester bond.  An enzyme known as a ligase ...

explant-culture-for-developmental-studies

Explant Culture for Developmental Studies

Explant culture is a technique in which living cells or tissues are removed from an embryo for continued development outside of the organism. This ex vivo ...

DNA Methylation Analysis

Methylation at CpG dinucleotides is a chemical modification of DNA hypothesized to play important roles in regulating gene expression. In particular, the ...

Expression Profiling with Microarrays

Microarrays are important tools for profiling gene expression, and are based on complementary binding between probes that are attached to glass chips and ...

Density Gradient Ultracentrifugation

Density gradient ultracentrifugation is a common technique used to isolate and purify biomolecules and cell structures. This technique exploits the fact ...

F&#246;rster Resonance Energy Transfer (FRET)

F&#246;rster resonance energy transfer (FRET) is a phenomenon used to investigate close-range biochemical interactions. In FRET, a donor photoluminescent ...

detecting-environmental-microorganisms-with-polymerase-chain-reaction

Detecting Environmental Microorganisms with the Polymerase Chain Reaction and Gel Electrophoresis

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
Demonstrating Author: Bradley Schmitz
Polymerase chain reaction (PCR) is ...

Gel Purification

Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, ...

Detecting Reactive Oxygen Species

Reactive oxygen species are chemically active, oxygen-derived molecules capable of oxidizing other molecules. Because of their reactive nature, there are ...

Gene Silencing with Morpholinos

Morpholino-mediated gene silencing is a common technique used to study roles of specific genes during development. Morpholinos inhibit gene expression by ...

development-and-reproduction-of-the-laboratory-mouse

Development and Reproduction of the Laboratory Mouse

Successful breeding of the laboratory mouse (Mus musculus) is critical to the establishment and maintenance of a productive animal colony. Additionally, ...

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

HS-LS1-1.

Measuring Size Changes with JND

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