Hearing someone whisper, noticing slight differences in shades of green, or hearing the volume change on the television. These are small changes yet impactful on how we understand stimulation. Ernst Weber would go on to explain what these tiny phenomena are and why they are so important.
- What was Ernst Weber’s contribution to Psychology?
- What did Weber mean by sensation and perception?
- What are the Ernst weber and Gustav Fechner psychophysical laws?
- What are some examples of Ernst Weber’s Law?
Ernst Weber's Contribution to Psychology
Ernst Heinrich Weber (Born on 24 June 1795) was a German physician before his notable works in psychology. Later in his life, Weber became a founder of experimental psychology and focused on sensation and touch and creating good techniques in experimental efforts.
Ernst would go on to focus his studies on a concept of a more concrete mapping of the nervous system and its functions. Weber theorized that there was a strong connection between the processes of the brain and our mental processes (psychophysics).
Psychophysics is the psychology sect that researches the relations between physical stimuli and our mental states or processes. Examples of physical stimuli could be pressure, weight, or temperature.
This path of thinking led Weber to an interest in kinesthesis. Because of this research, we have a modern understanding of physical sensations and touch. Weber’s analysis showed the relationship between our judgments based on physical sensations. This led to Weber’s law, one of his most notable contributions to psychology.
Kinesthesis is the body’s system for sensing the position and movements of our body parts.
Psychologist Edward Titchener considered Weber’s works to be foundational to experimental psychology.
Ernst Weber: Sensation and Perception
Ernst Weber's sensation and perception theories do not stop at Weber's law. Weber studied sensation and perception in other ways too. Ernst Weber's position on sensation and perception differed from the original approach to studying these subjects. By finding new ways of measuring sensitivity, Weber transformed the study of perception into an experimental discipline rather than an observational one through his research on tactile acuity.
Tactile acuity refers to the our perceived precision of touch.
Weber could measure (rather than simply observe) tactile acuity by determining the distance between two areas on our skin that we can easily perceive as two separate touches. This was referred to by Weber as the two-point threshold.
The two-point threshold is the distance on our skin that separates two pointed stimulations.
These theories led Weber to create new psychophysical laws alongside researcher Gustav Fechner.
Ernst Weber and Gustav Fechner’s Psychophysical Laws
Weber’s law, also known as the Weber-Fechner law, defines the perception of change we feel when there is a stimulus. The law states that the difference in the stimulus will be just noticeable from the original stimulus.
Just-noticeable difference: (aka difference threshold) the least amount of change between to stimuli that a person can detect 50% of the time.
This means that the change is so tiny that it can be hard to notice the difference between the two stimuli. There are no extreme changes in the felt or noticeable stimulus.
How did Weber come to these conclusions?
In 1834, Weber used this theory to explain weightlifting with his student Gustav Theodor Fechner. The experiment went something like this:
A volunteer is asked to hold a weight of 2.0 kg ( about 4.4 lbs) and reports some effort to hold the weight. Then, added to the 2.0 kg weight was another 0.05 kg. This weight addition seems insignificant to the volunteer holding the weights. The volunteer reports not feeling any additional effort to maintain the weight even when extra weight has been added up to 2.1 kg. So when will the volunteer finally notice that the weight is becoming increasingly heavier?
Fig. 1 The change in weight was hardly detectable to the volunteer.
If adding weight is continued, the volunteer would find that they will only notice the difference when the additional weight is equal to 0.2 kg.
This experiment showed that the threshold for noticing the difference or fluctuation in weight is just 0.2 kg. The 0.2kg weight difference in the experiment would be referred to as the just-noticeable difference.
Ernst Weber Law
These calculations are now formally known as Ernst Weber's Law. So how exactly did Weber and Fechner formulate the values in the above experiment? Well, it began first with Fechner's Fraction.
Fechner Fraction: I/I
Weber’s Law formula: ΔI/I = k – constant
The I is the original intensity or force of the stimulation.
ΔI is the added required difference to be noticed or felt (like the added weight in the earlier experiment).
k is a constant called Weber’s constant.
Weber’s law: states that two stimuli must differ by a constant percentage for the average person to detect any difference.
What is knowing noticeable differences impactful? Weber’s law helps us understand how people perceive different stimuli. Weber found that the constant percentage may change depending on the stimulus.
For you to notice a difference between two lights, the intensity must differ by 8 percent. However, to notice the difference between two weights, they must differ by only 2 percent.
Erst Weber’s Theory: Examples
Weber stated that his law applied to the stimulation we feel. We can feel stimulations, such as sound, weight or pressure, taste, and perceiving colors.
Your classmate needs your help! They must carry some notebooks to class but have run out of room in their backpack. You gladly say that you will carry some of the notebooks for them. You take one notebook to hold and notice that it’s not too heavy. Slowly, your friend gives you another notebook to carry for them. You don’t feel any change in the effort it takes to carry these notebooks. There are more notebooks that your friends need help with. You take another to hold. Now, you can feel a slight difference in the weight of the notebooks and the effort you are using to carry them all.
This small amount of weight change that is felt is the just-noticeable difference.
You watch television with your sister or brother after school, but the sound volume is too low to hear. You ask them to turn up the volume so that you can hear. They press the volume button twice, but you still cannot tell the difference in the volume. Your brother or sister presses the button twice more times before you notice that the volume has increased.
That small amount of volume that changed would be the just-noticeable difference.
You volunteer for a psychology experiment at your school in the cafeteria. The researchers give you small portions of sugar in a cup of water and ask you to drink it. The researcher asks you to say when you notice the sweetness of the water versus the taste of plain water.
The minor level of sweetness you can taste half the time is the just difference threshold.
You are making a poster for your history class project. You are coloring a landscape with markers, and you are working quickly. After you finish coloring the portion of the landscape that is the sky, you notice that you have been using two types of the color blue! Looking at the poster, you can barely tell when the color has changed.
This very subtle and small difference I color you noticed is called the just difference threshold.
Fig. 2 At what point do the colors become light or dark?
Ernst Weber - Key takeaways
Ernst would go on to focus his studies on a concept of a more concrete mapping of the nervous system and its functions.
This path of thinking led Weber to an interest in kinesthesis. Because of this research, we have a modern understanding of physical sensations and touch.
Weber’s law, also known as the Weber-Fechner law, defines the perception of change we feel when there is a stimulus. The law states that the difference in the stimulus will be just noticeable from the original stimulus.
The just noticeable difference(JND), is also known as the difference threshold or limen. This is the minimum level of stimulation that can be detected.
Weber’s law shows that the perception of stimuli is relative and not absolute.
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