An absolute threshold is the smallest level of stimulus that can be detected, usually defined as at least half the time. The term is often used in neuroscience and experimental research and can be applied 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.
However, it is important to note that at such low levels, participants 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 percent of the time.
In 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. An example of this might be measured at what levels participants can detect the ticking sound of a clock.
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.
In 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 detect 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.
For odors, the absolute threshold involves the smallest concentration that a participant is able to smell. An example of this would be to measure what the smallest amount of perfume that a subject is able to smell in a large room.
One important thing to note is that 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, characteristics of the participants, and environmental factors. 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.
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 Can Influence the Absolute Threshold
While the absolute threshold is often thought of purely in terms of sensation and perception, a number of factors can play a role including expectations, motivations, and thoughts. For example, if you are expecting to hear a noise, you might be more likely to detect it at lower levels than you would if you do not expect to hear the noise.
Researchers have found that women tend to have lower absolute threshold than men, meaning they are better able to detect lower levels of sight, smell, taste, touch, and sound. Introverted people have also been found to be better able to detect stimulus levels at lower levels. However, absolute thresholds are also prone to change as people grow older. When people are younger, they are able to detect energy levels at lower levels but require greater stimulation to detect these same stimuli when they are older.
A Word From Verywell
The absolute threshold serves as an important tool for researchers studying the capabilities and limitations of human sensation and perception. 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, which is the smallest possible detectable difference between two stimuli.
Doty, RL & Laing, DG. Psychophysical measurement of human olfactory function. In RL Doty (Ed). Handbook of Olfaction and Gustation. New York; John Wiley & Sons; 2015.
Gelfand, SA. Hearing: An Introduction to Psychological and Physiological Acoustics, 5th ed. Boca Raton, FL: Taylor & Francis Group; 2009.
Shepherd, D, Hautus, MJ, & Urale, PWB. Personality and perceptions of common odors. Chemosensory Perception. 2017;10(1-2);23-30.
My enthusiasm to study psychology began as a child due to living with an alcoholic. Through observing and being around someone with such a social problem I was gaining first hand experience of what it was like to live with someone with an addiction. It ignited an interest into human behaviour and what a person's line of thought is when dealing with such a challenge.
This developed into an ambition to be able to eventually work in an environment which helps people with mental health issues.
During school certain interests of mine became clearer. In fifth year my favourite subject was modern studies where I gained a better insight into social behaviour trends in Britain, which gave me a clearer understanding of how the choices we make impact social problems. When studying this topic I chose to become an organ donor.
The amount of statistics in Modern Studies has improved my maths skills. This I believe will be essential when studying psychology at university. In sixth year I chose to study higher psychology which has made me eager to study this subject to post graduate level.
I feel that it has gave me a good insight to what psychology is about and has helped my understanding of concepts and skills needed at university level, for instance research skills, keeping notes and deadlines organised and increasing independent reading.
I feel it has familiarised me with the course, thus making me determined to study it to doctorate level. In addition I am studying Religious, Moral and Philosophical Studies at advanced higher level. I am confident this has improved my critical thinking skills which will be extremely useful when completing my degree.
Studying at this level has developed my independent study skills, vital for university life as the workload requires many hours of studying out of class time. It has also introduced me to researching and writing a dissertation. I based my dissertation on the existence of god and the theory of evolution.
Choosing to do this as my dissertation has opened my mind to using scientific concepts as arguments, for instance the laws of physics when using the Big Bang as an argument against the existence of god. I had to read about many people's view points, including those from different religions and philosophical backgrounds.
This along with modern studies has built my debating skills to a good level, and I believe that I can work well in a team when debating, or independently. I feel that studying psychology and religious, moral and philosophical studies this year are working well together as both of these subjects require a great deal of thinking and organisation.
During free periods in school, I am part of the fifth and sixth year Events Committee which requires me to work in a team and come to decisions based on other people's opinions as well as my own. I am also a school prefect and this displays responsibility and dedication to the school.
In my own time I have undertaken two short courses at Glasgow School of Art. The first being in fashion and textiles as I like to dress make often. It developed concentration skills to complete tasks that I was not completely familiar with. The second course is life drawing. Each lasts twenty weeks and as it is set in a higher education environment I feel it has given me a good insight into university life.
I also attended a week at Castle Toward where I studied photography. The week was split into independent study and team building exercises.
My photograph was chosen to advertise the exhibition created during Castle Toward by Glasgow City Council and was seen on many flyers and posters around Glasgow.
To confirm my career choice I arranged a meeting with a psychologist, this proved to me that studying to a doctorate level is my aim and I would like to be a part of this team in the future.
I am confident that my first step to achieving this is by studying psychology at undergraduate level which I am eager to begin.