北大心理学系.心理物理学方法与Matlab实现

Psychophysical functions
费希纳的三个问题
• 第一、觉察给定刺激所必 需的最小物理刺激是什么？ 这个问题同绝对阈限(AL) 有关。
• 第二、觉察两个不同刺激 量所需的最小物理差别是 什么？这涉及差别阈限 (DL)。
Gustav Theodor Fechner 1801–1887
constant slope
Stimulus intensity
• Linear function difference threshold (slope) is constant
• An observer able to detect the difference between intensities 100 and 110 should also be able to detect the difference between 1000 and 1010. This is not the case: the observer is able to detect the difference only between 1000 and 1100
心理物理学方法和matlab实现 2015-6-21
References
• Watson and Pelli (1983) QUEST: A Bayesian adaptive psychometric method.
• Leek (2001) Adaptive procedures in psychophysical research.
Linear psychophysical
equation
X-intercept
slope
Stimulus intensity
If a linear relationship is assumed, two values determine the function:
– X-intercept: minimum stimulus value that evoked any sensation; absolute threshold
– 绝对阈限（Absolute threshold）: intensity that the observer can just barely detect
• Intensities below absolute threshold: undetectable • Intensities above absolute threshold: detectable
• Strasburger (2001) Converting between measures of slope of the psychometric function.
• Strasburger (2001) Invariance of the psychometric function for character recognition across the visual field.
• Grassi and Soranzo (2009) MLP: a MATLAB toolbox for rapid and reliable auditory threshold estimation.psychoacoustics
• http://www.palamedestoolbox.org/
内省法
• 早期心理学家采用的方法(Wundt)
• 对有意识思考和感知的自我观察
– Do I perceive this light brighter than that? Why?
• 因其主观性而被科ቤተ መጻሕፍቲ ባይዱ的方法所拒绝 • 但提供“先见之明”，有利于设计实验和形成假
说。 •
– I realized that it is hard for me to hear very high and very low tones. Thus the frequency of a tone may be a factor in its perceived loudness/audibility. Let’s test this in an experiment!
– Slope: the rate at which sensation grows as we increase intensity; difference threshold (inversely proportional to slope)
Thresholds
General definitions (not assuming linearity):
• 第三、判别两个刺激在心 理感觉上相等的条件是什 么？这是主观相等点(PSE) 的问题。
心理物理实验法
• 古典心理物理学的基本问题
在精心控制的实验条件下，刺激的变化直接对应 于感觉的变化
心理物理学研究的目的在于决定外部世界的一致 性规律-韦伯定律
阈限(Thresholds)
Sensation magnitude
• 500 & 550 Hz tones
• 5000 & 5050 Hz tones
• 5000 & 5500 Hz tones
• A change in intensity that is larger than the difference threshold: detectable
Difference thresholds
Sensation magnitude
Linear psychophysical
equation
– 差别阈限（Difference threshold） (just noticeable difference /JND/ and difference limen): minimum intensity difference that is noticeable to the observer
• A change in intensity that is smaller than the difference threshold: undetectable