Student Resources Study Guides and Tips What Is the Absolute Threshold of a Stimulus? By Kendra Cherry, MSEd Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book." Learn about our editorial process Updated on September 07, 2023 Fact checked Verywell Mind content is rigorously reviewed by a team of qualified and experienced fact checkers. Fact checkers review articles for factual accuracy, relevance, and timeliness. We rely on the most current and reputable sources, which are cited in the text and listed at the bottom of each article. Content is fact checked after it has been edited and before publication. Learn more. by Adah Chung Fact checked by Adah Chung Adah Chung is a fact checker, writer, researcher, and occupational therapist. Learn about our editorial process Print Elizabeth Knox / Getty Images Table of Contents View All Table of Contents Sound Sight Smell Touch Influential Factors Absolute vs. Difference Threshold Trending Videos Close this video player An absolute threshold is the smallest level of stimulus that can be detected, usually defined as at least half the time. It's a term that is often used in neuroscience and experimental research. It can also apply to any stimulus that can be detected by the human senses, including sound, touch, taste, sight, and smell. For example, in an experiment on sound detention, researchers may present a sound with varying levels of volume. The smallest level that a participant is able to hear is the absolute threshold. When a stimulus is at a very low level, however, we may only detect the stimulus part of the time. Because of this, the absolute threshold is usually defined as the smallest level of a stimulus that a person is able to detect 50% of the time. At a Glance The absolute threshold is an important tool for researchers studying the capabilities and limitations of human sensation and perception. It is defined as the lowest stimulus level that an organism can detect at least half the time. These limits can vary depending on factors such as motivation, expectation, and attention. In other words, there is no single absolute threshold for any sensory experience. It may vary from person to person and from one situation to the next. How the Experimental Method Works Absolute Threshold for Sound For hearing, the absolute threshold refers to the smallest level of a tone that can be detected by normal hearing when there are no other interfering sounds present. Whether you can detect a the ticking of a clock in a quiet room would be an example. Young children generally have a lower absolute threshold for sounds since the ability to detect sounds at the lowest and highest ranges tends to decrease with age. Absolute Threshold for Sight For vision, the absolute threshold refers to the smallest level of light that a participant can detect. Determining the absolute threshold for vision might involve measuring the distance at which a participant can detect the presence of a candle flame in the dark. For example, imagine that you are a participant in a psychology experiment. You are placed in a dark room and asked to say when you are first able to detect the presence of light at the other end of a long room. In order to determine the absolute threshold, you would go through a number of trials. During each trial, you would signal when you are first able to detect the presence of light. The smallest level that you are able to detect half of the time is your absolute threshold for light detection. In one classic experiment, researchers found that after controlling for dark adaptation, wavelength, location, and stimulus size, the human eye was able to detect a stimulus between the range of 54 and 148 photons. Absolute Threshold for Smell For odors, the absolute threshold involves the smallest concentration that a participant is able to smell. An example of this would be to measure the smallest amount of perfume that a subject is able to smell in a large room. The absolute threshold for smell can vary considerably depending upon the type of odor used, the dilution methods, the data collection methods the researchers are utilizing, environmental factors, and individual characteristics. For example, one study found that certain personality traits can influence how we detect scents. Even the time of day that data is collected can have an influence on the absolute threshold. Environmental factors such as pressure and humidity can also influence how well participants are able to detect smells. Absolute Threshold for Touch The amount of force required for you to detect the feeling of a feather lightly brushing your arm is an example of the absolute threshold for touch. When it comes to touch, the level of stimulation required to detect the stimulus can vary dramatically depending upon the part of the body that is being touched. For example, the absolute threshold of detecting touch may be much lower at your fingertips versus that of the back of your neck. Factors That Impact the Absolute Threshold While the absolute threshold is often thought of purely in terms of sensation and perception, factors such as our expectations, motivations, and thoughts influence whether we can detect a stimulus. For example, if you expect to hear a noise, you might be more likely to pick up on it at lower levels than if you weren't expecting it. Researchers have found that women tend to have lower absolute thresholds than men, meaning they can better detect lower levels of sight, smell, taste, touch, and sound. Introverted people have also been found to be better able to sense a stimulus at lower levels. Absolute thresholds aren't constant; they are prone to change as we grow older. When we are younger, we can detect things at lower levels. As we age, however, we begin to need increased stimulation to detect those same sensory events. Absolute Threshold vs. Difference Threshold One important thing to remember is that researchers distinguish between the ability to detect a stimulus and the ability to tell the difference between stimulus levels. The absolute threshold should not be confused with the difference threshold. The difference threshold is the minimum difference between two stimuli that is detectable. Like the absolute threshold, the difference threshold is the minimum difference that can be detected at least 50% of the time. The difference threshold is also known as the just noticeable difference. Some examples include: How much of a difference there must be in order to tell the difference in intensity between two different light bulbsHow much a sounds needs to increase to tell that the noise has become louderHow much salt you need to add to your food to be able to tell a difference in flavor In the case of the difference threshold, the just noticeable difference between two stimuli is a constant proportion of the original stimulus (a principle known as Weber's law). If the intensity of the original stimulus is considerable, you are less likely to notice small changes. How Bottom-Up Processing Works 8 Sources Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. American Psychological Association. Absolute threshold. APA Dictionary of Psychology. Humes LE, Busey TA, Craig JC, Kewley-Port D. The effects of age on sensory thresholds and temporal gap detection in hearing, vision, and touch. Atten Percept Psychophys. 2009;71(4):860-871. doi:10.3758/APP.71.4.860 Hecht S, Shlaer S, Pirenne MH. Energy, quanta, and vision. J Gen Physiol. 1942;25(6):819-840. doi:10.1085/jgp.25.6.819 Shepherd D, Hautus MJ, Urale PWB. Personality and perceptions of common odors. Chem Percept. 2017;10(1-2):23-30. doi:10.1007/s12078-016-9220-4 Nagappan PG, Subramaniam S, Wang D. Olfaction as a soldier-- a review of the physiology and its present and future use in the military. Military Med Res. 2017;4(9). doi:10.1186/s40779-017-0119-4 Tamè L, Azañón E, Longo MR. A conceptual model of tactile processing across body features of size, shape, side, and spatial location. Front Psychol. 2019;10:291. doi:10.3389/fpsyg.2019.00291 Park YH, Shin SH, Byun SW, Kim JY. Age- and gender-related mean hearing threshold in a highly-screened population: The Korean National Health and Nutrition Examination Survey 2010–2012. PLoS One. 2016;11(3):e0150783. doi:10.1371/journal.pone.0150783 Bolders AC, Tops M, Band GPH, Stallen PJM. Perceptual Sensitivity and Response to Strong Stimuli Are Related. Front Psychol. 2017;8:1642. doi:10.3389/fpsyg.2017.01642 By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book." See Our Editorial Process Meet Our Review Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Helpful Report an Error Other Submit