A difference threshold, also known as just noticeable difference (JND), is the smallest difference between two stimuli humans can perceive. In other words, it is the minimum degree of change that individuals can notice or detect.
For example, a person may notice a slight temperature change in the room once it is at least a degree or two higher or lower than what they already feel.
The concept of difference threshold applies to all five senses: touch, taste, smell, hearing, and vision. Besides, it is useful for noting changes in luminosity, sweetness levels, weight or pressure range, and sound intensity variations.
This concept is widely used in psychology and marketing, as it helps explain how humans perceive environmental changes.
Definition of Difference Threshold
A difference threshold is the lowest amount of change that an individual can detect or recognize. It is measured in terms of how many “just noticeable differences” (JNDs) exist between two stimuli (Meilgaard et al., 2007).
It also determines how sensitive a person is to certain stimuli and can be used to predict how often someone will react to a change.
According to Houston and colleagues (2013), a difference threshold is defined “as the level of difference that is detectable 50% of the time” (p. 84).
For instance, if you were to hold two items of varying weights in each hand, the slightest weight difference between them that you could sense half of the time would be referred to as your “just noticeable difference.”
So, in simple terms, a difference threshold is the smallest perceivable difference between two stimuli.
10 Examples of Difference Threshold
- Vision: Subtle shifts of coloring, perceivable to the naked eye, are known as visual thresholds. If two colors are close enough in hue and value, they might not be discernible to the human eye. The minimally perceptible difference between these two similar colors is known as the difference threshold.
- Taste: In terms of taste, we can explore the smallest detectable change in sweetness or sourness. So, the minimum difference in the quantity of sugar in the cake a person can taste is known as the difference threshold.
- Smell: The minutest difference in scent intensity is referred to as the smell threshold. The smallest detectable change in the amount of an aroma or fragrance is known as the difference threshold.
- Hearing: Similarly, when it comes to sound intensity or pitch, we can assess the minimum amount of change that one can sense between two similar sounds. So, the minimum change in the TV volume a person can perceive is known as the hearing difference threshold.
- Touch: The touch threshold is the slightest detectable variation in temperature. If, for example, a person feels a difference in temperature when touching two objects, the minimum perceivable change in heat between them is known as the touch threshold.
- Weight: The smallest variation in weight a person can detect between two objects is known as the “weight difference threshold.” In other words, if someone holds up two pens of differing weights and is asked to differentiate them, they may not be capable until there’s an ample difference.
- Pressure: Likewise, the pressure threshold is the minimum detectable difference in pressure between two stimuli. To put it another way, if a person tries to identify variations in pressure between two objects, they may not be able to detect any until the amount of pressure reaches an identifiable level.
- Luminance: The luminosity difference threshold is the minimum detectable change in brightness between two stimuli. For instance, minuscule fluctuations in light intensity are enough for humans to differentiate between two lighting sources.
- Size: The size difference threshold is the minimum size change between two objects that a person can detect. So, holding two boxes of different sizes in each hand, the person may not be able to tell the difference until one of them is much bigger than the other.
- Time: The temporal difference threshold is the minimum amount of time between two successive events that a person can perceive. For instance, if two events are presented in quick succession, the person may not be able to tell the difference until there is a considerable passage of time between them.
Origins of Difference Threshold
Ernst Weber, a renowned physiologist, was the one who initially articulated the difference threshold concept. This theory was later further developed by another well-known psychologist Gustav Fechner.
Weber was the first one who highlights that two stimuli must be spaced a certain degree apart to be perceived. His research additionally discovered this minimal difference is typically a fraction of the average magnitude between them.
He introduced a law called the Weber law, which states that “the change in a stimulus that will be just noticeable is a constant ratio of the original stimulus” (Wurm, 2022, p. 165).
Later, Fechner used Weber’s law to expand the concept of difference threshold further and proposed that any two similar stimuli can be distinguished by people only if they are different in intensity (Link, 2020).
He termed this theory as the “just noticeable difference” (JND), which is widely employed in many disciplines to describe the difference between two stimuli.
While Weber highlights that a perceptible increase in sensation is proportionate to the present stimulus, Fechner’s law is inferred from Weber’s (with further assumptions), stating that our sense of intensity grows more gradually with a rise in energy — not at the same rate.
Absolute Threshold vs. Difference Threshold
The absolute threshold denotes the smallest possible level of stimulus that an individual can perceive through their senses, while a difference threshold refers to the smallest variance between two stimuli that someone can see or feel.
Absolute thresholds are usually associated with the individual’s ability to detect a single stimulus. It is the minimum intensity of any given stimulus that an individual can sense without background noise or other stimuli (Meligaard et al., 2007).
On the other hand, difference thresholds are related to a person’s ability to identify the distinctions between two stimuli. It is the minimum amount of disparity between two similar stimuli that a person can single out and differentiate (Meligaard et al., 2007).
The absolute threshold serves as an indication of how much stimulus change the subject can detect and remember, whereas the difference threshold determines the smallest detectable amount of deviation in given stimuli.
The absolute threshold is usually measured in physical units, such as decibels or degrees Celsius.
The difference threshold, however, may differ based on the type of stimuli and can sometimes be measured in psychological units, such as identical points or just noticeable differences (JND).
How Difference Threshold is Calculated
The difference threshold is calculated by assessing the subject’s response to two similar stimuli, one of which has changed (Meligaard et al., 2007).
This is determined by the smallest level of change that the subject can perceive.
To measure the difference, two different stimuli must be tested. The reference stimulus is used as the foundation for comparison and remains constant.
Afterward, a slight alteration to the second stimulus is made before asking subjects if they can detect any changes.
When the subject is unable to differentiate between two levels of intensity, it indicates the difference threshold has been reached.
Importance of Difference Threshold
By exploring threshold differences and other related phenomena, scientists can gain insights into how humans perceive their environment and where misinterpretations may occur.
1. Understanding human perception
The difference threshold is crucial in understanding how humans perceive their environment.
By studying the difference threshold, researchers can better understand how different stimuli are perceived by an individual and how they could be incorporated into everyday communication and media.
2. Enhancing communication
A better understanding of the difference threshold can help improve communication between individuals and machines. Companies can use this knowledge to create more intuitive and interactive interfaces that provide users with a better experience.
3. Improving accuracy
By understanding the difference threshold, companies can create more accurate systems that measure data to a higher degree of accuracy. This could help them make better decisions when it comes to creating new products and services.
4. Enhancing marketing strategies
In many cases, companies use the difference threshold to create more effective marketing strategies.
By understanding what aspects of products people find most pleasing, they can focus their resources on improving those areas and boosting sales.
5. Developing better products
When designing new and better products, researchers often examine the just noticeable difference (JND).
For example, when phone manufacturers are crafting their devices, they are careful to measure and evaluate the JND of sound volume levels to ensure that people can clearly hear their music and calls.
A difference threshold is important in understanding how humans perceive and differentiate between stimuli. It measures the smallest possible change that an individual can detect.
This concept can be used to improve communication between individuals and machines, enhance accuracy in data collection, and create more targeted marketing strategies.
It is also important for developing better products that people will be able to use with ease.
With a deeper understanding of difference thresholds, researchers can continue to develop new and exciting ways for people to interact with the world around them.
Houston, J. P., Bee, H., & Rimm, D. C. (2013). Invitation to psychology. Academic Press.
Link, S. W. (2020). The wave theory of difference and similarity. Routledge.
Meilgaard, M., Civille, G. V., & Carr, B. T. (2007). Sensory evaluation techniques. Taylor & Francis.
Wurm, S. (2022). Consensus realities. ATICE LLC.