Thresholds theory of classical psychophysics essay

Complete information on the Signal-detection theory of psychophysics? The signal detection theory is an alternative to the approaches of classical psychophysics. It emphasizes that the judgment about the presence or absence of a stimulus depends on two processes:

Thresholds theory of classical psychophysics essay

Neuroscience methods recording action potential firing rates from single neurons, studying brain anatomy, neuroimaging, etc. But they can not, by themselves, solve the puzzles of sensation and perception.

To understand a complicated system, it is not enough to know only the workings of its individual components.

If you know only how those components work, you still do not know what the car is for, or any of the principles of electricity and combustion and other factors governing the behavior of a car engine.

Perception Lecture Notes: Psychophysics

To understand the entire functioning of a car you must know not only the kinds of parts it is constructed from, but also the way these parts fit together and the purpose that the car is designed for. This is a theme that we'll come back to again and again in this course.

Studying the brain and its component parts can only get us so far in our understanding of perception. We need, in addition, to perform behavioral experiments. The goal is to interpret the brain activity in terms of perception and perceptually guided behavior.

For example, what's the relationship between auditory nerve firing rates and perceived loudness or perceived pitch? What's the relationship between photoreceptor response and perceived brightness or perceived color? The starting point for studying perception is to come up with a phenomenon.

It might be an illusion Or an observation e. Many of the basic phenomena in vision and hearing were discovered and described by Helmholtz in the late 19th century. For the last years or so we have been trying and are still trying to explain those phenomena.

Thresholds theory of classical psychophysics essay

Some perceptual scientists spend their entire careers coming up with new perceptual phenomena illusions, etc. This is more of an art than a scientific method, so I can't really tell you how to do it.

Ultimately, we want to establish a causal link demonstrating that a particular neural mechanism causes a particular perceptual phenomenon. To establish a strong link between perception and neurophysiology, we need to have quantitative measurements of both, and we need to show that they are consistent with one another.

So next we will cover how we quantify perceptual phenomena. There are three basic experimental protocols that we use in perceptual psychology experiments: For example, you might adjust the intensity of two different tones so that they sound equally loud.

Matching experiments are also sometimes done by presenting a series of trials and simply having the subject pick which trial had the best match.

For example, each trial might consist of two tones and the subject picks the trial in which the tones sounded closest in loudness. We'll see several examples of matching experiments later on in the course. In a detection experiment, the subject's task is detect small differences in the stimuli.

Thresholds theory of classical psychophysics essay

But how, in fact, do we go about doing a detection experiment? There a number of methods that people have used over the years. Some are quick and simple but not very powerful. The method of adjustment: Ask observer to adjust the intensity of the light until they judge it to be just barely detectable.

This is like what happens when you get fitted for a new prescription for eye glasses. Typically, the doctor drops in different lenses and asks you if this lens is better than that one. Something is very unsatisfying about the method of adjustment: With this method, one is asking the observer to tell us what they think their own threshold is.

When subjects are very inexperienced - and indeed, even when they are quite experienced - this can be a dangerous strategy. It is not so much that the subject is lying or being dishonest. Rather, it is simply difficult to judge when a light is on the threshold of visibility.

Moreover, it's kind of stressful for the subject - does this lens work better or does that one work better?In spite of the scientific articles questioning the classical threshold concept, several recent papers use this concept to model and explain psychophysical experimental results in the tactile system [7,8,11,16,29,30], not as a mere definition but as the core of the reasoning.

Classical psychophysics considered the detection of a given stimulus strictly a function of its intensity, acting upon some physical sensory apparatus whose response was a step-function defining.

William James, Gustav Fechner, and Early Psychophysics

Classical threshold theory G ab r i el B au d-B o vy Fondamental definitions 2 Testing the high-threshold theory G ab r i el B au d-B o vy A modern view of thresholds 14 Transduction S process Σ Σ R Observer psychological state Its use in Psychophysics is due to Tanner, Swets and colleagues.

The signal detection theory is an alternative to the approaches of classical psychophysics. It emphasizes that the judgment about the presence or absence of a stimulus depends on two processes: (a) an initial sensory process, which involves subject's sensitivity to the intensity of a stimulus, and.

This article has been published in the can cite it as: Landers, R.N.

Fechner and James: Scientist–Philosophers

(). Computing intraclass correlations (ICC) as estimates of interrater reliability in SPSS. Oct 04,  · This essay follows a similarly mosaic-like structure, providing a brief account of Fechner’s psychophysics and its influence on James, in the context of the early history of experimental psychology, the field that served as the final wedge dividing philosophy from psychology.

Intraclass Correlations (ICC) and Interrater Reliability in SPSS