Table of ContentsView AllTable of ContentsDefinitionImportanceHistoryMeasuringExamplesUses

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Sometimes the difference between two things is glaring, like with a red car and a blue sedan. Other times it is barely noticeable, such as whether a toothbrush has 2,500 or 10,000 bristles. The amount of difference required for us to recognize that two items aren’t the same is known as the just noticeable difference (JND).

Here we do a deeper dive into what the just noticeable difference is, why it’s important, and how it was discovered. We also share how JND is measured, a few examples in everyday life, and how it is used to impactour buying decisions.

What is the Just Noticeable Difference?

The just noticeable difference, also known as the difference threshold, is the minimum level of stimulation that a person can detect 50% of the time.For example, if we were asked to hold two objects of different weights, the just noticeable difference would be the minimum weight difference between the two that we could sense half of the time.

Just noticeable difference is part of a field of study known as psychophysics. Psychophysics examines how physical stimuli in the environment affect and interact with mental processes. While scientists used to focus on measuring objective data, psychophysics allows them tomeasure subjective experiencesas data.

The just noticeable difference applies toall five senses: touch, taste, smell, hearing, and sight. It can also apply to things such as brightness, sweetness, weight, pressure, and noisiness, among other factors.

Difference Threshold vs. Absolute Threshold

The just noticeable difference is not the same as theabsolute threshold. While the difference threshold between two stimuli involves detecting differences in stimulation levels, the absolute threshold refers to the smallest detectable level of stimulation.

The absolute threshold for sound, for example, would be thelowestvolume level that a person could detect. The just noticeable difference would be the smallestchangein volume that a person could sense.

Importance of JND

Difference thresholds can help researchers understandhow we respond to our environment. It also gives insight into where our senses are subject to error, such as in not being able to detect the differences between two things.

The just noticeable difference also impacts our preferences. For example, it can affect whether we prefer to drink skim, low-fat, or full-fat milk as each is slightly different in taste and visual appearance.

History of the JND Concept

Weber studied the just noticeable difference using weights to see when subjects could detect when the weight was different. He discovered that we’re better at detecting relative differences. In other words, when the weights got heavier, subjects needed a bigger difference between them to notice they were different.

How Just Noticeable Difference Is Measured

The measurements scientists take depend on the sensory information being received. For instance, when measuring heat, researchers may use joules. When measuring sound, they may use decibels instead.

Neural Activity

Our brains receive sensory input (such as light, sound, or taste), and our sensory organs convert this input into electrical signals.Therefore, measuringneural activityis another way in which researchers may determine how much (and what type of) sensory input a person is receiving.

Looking at a person’s brain activation patterns seems to be a good way of measuring the just noticeable difference. For example, in one study, researchers found they could distinguish whether or not someone was touching something sticky based on their neural activity.

Stimulus Intensity

The intensity level of the stimulus can also play a role in how much people notice any changes. If a light is very dim, people may be more likely to notice smaller changes in intensity than they would if those same changes were made to brighter light.

For example, imagine being in a dark movie theater. When the house lights slowly start to turn on, this small change in the light intensity is immediately noticeable. However, upon leaving the theater and heading outside where the sun is shining brightly, these same changes in light intensity might be less noticeable since the stimulus level is much higher.

Does Just Noticeable Difference Change?The just noticeable difference does change throughout the day. The amount and intensity of otherstimuli experienced beforehandalso affect how we perceive additional stimuli.

Does Just Noticeable Difference Change?

The just noticeable difference does change throughout the day. The amount and intensity of otherstimuli experienced beforehandalso affect how we perceive additional stimuli.

Examples of the Just Noticeable Difference

The following are everyday examples in which the just noticeable difference can be observed.

Touch

Imagine that during apsychology experiment, researchers ask all participants to hold two small amounts of sand in each hand. They slowly add tiny amounts of sand to one hand and ask when the subjects notice that one hand feels heavier than the other. The smallest weight difference that can be detected at least half the time is the just noticeable difference.

Sound

Another example of the just noticeable difference is watching television with someone else, but the volume is too low for us to hear. We ask them to turn it up and they press the volume button twice, but we still can’t tell a difference. They then press the button two more times before we can notice an increase in volume.

Taste

Sight

We dye our hair but afterward, the color still looks the same as it did before. This may be because we dyed it a similar shade to what we already had, and the color isn’t above the difference threshold.

Uses for the Just Noticeable Difference

The JND is often studied in product development. For instance, when manufacturing cell phones, companies measure the JND of sound so there are noticeable increases when the volume is raised on the device. Companies that create food products can also study the JND to understand consumer preferences.

Companies may take advantage of the JND in several ways. For instance, a company may determine the JND of a price point. This enables it to increase the price of a product so slightly that consumers likely won’t notice it.

Downsizing packaging saves companies money, but it’s often seen as an unethical practice—“tricking” the consumer into buying their favorite products at the same (or higher) prices, so they’re getting less without knowing it.

7 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Psychological Association.Difference threshold.American Psychological Association.Psychophysics.McCarthy KS, Lopetcharat K, Drake MA.Milk fat threshold determination and the effect of milk fat content on consumer preference for fluid milk.J Dairy Sci. 2017;100(3):1702-1711. doi:10.3168/jds.2016-11417Lawson E.Debrief: Making a just noticeable difference.Br J Gen Pract. 2020;70(692):122. doi:10.3399/bjgp20X708533Privitera AJ.Sensation and perception. In:Noba Textbook Series: Psychology.Kim J, Yeon J, Ryu J, et al.Neural activity patterns in the human brain reflect tactile stickiness perception.Front Hum Neurosci. 2017;11:445. doi:10.3389/fnhum.2017.00445Çakır M, Balagtas JV.Consumer response to package downsizing: Evidence from the Chicago ice cream market.J Retail.2014;90(1):1-12. doi:10.1016/j.jretai.2013.06.002

7 Sources

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.American Psychological Association.Difference threshold.American Psychological Association.Psychophysics.McCarthy KS, Lopetcharat K, Drake MA.Milk fat threshold determination and the effect of milk fat content on consumer preference for fluid milk.J Dairy Sci. 2017;100(3):1702-1711. doi:10.3168/jds.2016-11417Lawson E.Debrief: Making a just noticeable difference.Br J Gen Pract. 2020;70(692):122. doi:10.3399/bjgp20X708533Privitera AJ.Sensation and perception. In:Noba Textbook Series: Psychology.Kim J, Yeon J, Ryu J, et al.Neural activity patterns in the human brain reflect tactile stickiness perception.Front Hum Neurosci. 2017;11:445. doi:10.3389/fnhum.2017.00445Çakır M, Balagtas JV.Consumer response to package downsizing: Evidence from the Chicago ice cream market.J Retail.2014;90(1):1-12. doi:10.1016/j.jretai.2013.06.002

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

American Psychological Association.Difference threshold.American Psychological Association.Psychophysics.McCarthy KS, Lopetcharat K, Drake MA.Milk fat threshold determination and the effect of milk fat content on consumer preference for fluid milk.J Dairy Sci. 2017;100(3):1702-1711. doi:10.3168/jds.2016-11417Lawson E.Debrief: Making a just noticeable difference.Br J Gen Pract. 2020;70(692):122. doi:10.3399/bjgp20X708533Privitera AJ.Sensation and perception. In:Noba Textbook Series: Psychology.Kim J, Yeon J, Ryu J, et al.Neural activity patterns in the human brain reflect tactile stickiness perception.Front Hum Neurosci. 2017;11:445. doi:10.3389/fnhum.2017.00445Çakır M, Balagtas JV.Consumer response to package downsizing: Evidence from the Chicago ice cream market.J Retail.2014;90(1):1-12. doi:10.1016/j.jretai.2013.06.002

American Psychological Association.Difference threshold.

American Psychological Association.Psychophysics.

McCarthy KS, Lopetcharat K, Drake MA.Milk fat threshold determination and the effect of milk fat content on consumer preference for fluid milk.J Dairy Sci. 2017;100(3):1702-1711. doi:10.3168/jds.2016-11417

Lawson E.Debrief: Making a just noticeable difference.Br J Gen Pract. 2020;70(692):122. doi:10.3399/bjgp20X708533

Privitera AJ.Sensation and perception. In:Noba Textbook Series: Psychology.

Kim J, Yeon J, Ryu J, et al.Neural activity patterns in the human brain reflect tactile stickiness perception.Front Hum Neurosci. 2017;11:445. doi:10.3389/fnhum.2017.00445

Çakır M, Balagtas JV.Consumer response to package downsizing: Evidence from the Chicago ice cream market.J Retail.2014;90(1):1-12. doi:10.1016/j.jretai.2013.06.002

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