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Dichotic listening (DL)

How the brain processes auditory information

What is dichotic listening?

Dichotic listening is a noninvasive technique in psychology and neuroscience that heps us understand how both sides of the brain process language. This technique works by playing auditory stimuli to each ear in order to observe and analyse how each side reacts.

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Which hemisphere is dominant for language?

For most people, the left hemisphere of the brain is the powerhouse in charge of language processing. It is responsible for producing language, figuring out what words mean, understanding sentences, and putting thoughts into words.

What is the process of dichotic listening testing?

Performing the dichotic listening test is very simple. It consists of putting on headphones and hearing two different sounds at the same time—one in your right ear and one in your left ear. This test is a controlled experiment that offers valuable insight into how the brain prioritises, analyses, and comprehends auditory signals, focusing on attention, memory, and language processing.

The evolution of auditory perception theories

There are several theories that explain how our brain processes information, including the Active Search Model, the Cross-Modal Influence Model, the Cherry Model, the Broadbent Model, and the Treisman Attenuation Model. However, in this article, we will focus on the last three.

The Cherry Model - Selective Filter Theory

Also known as the Selective Filter Theory, this theory was introduced in 1958 by Donald Broadbent and later refined by Colin Cherry. This theory suggests that our brain filters sounds, concentrating on one while ignoring others. This phenomenon is also known as the "cocktail party problem".

The Broadbent Model - Attenuative Filtering

Also known as the attenuative Filtering Model, this theory was also introduced in the 1950s by Donald Broadbent. Unlike the Cherry Model, it covers both auditory and visual perception. It suggests that the brain filters information from channels we aren't focusing on, reducing intensity without getting rid of them entirely. It helps us understand how the brain handles multiple stimuli without overwhelming the perceptual system.

The Treisman Attenuation Model

The Treisman Attenuation Model was introduced in 1964 by Anne Treisman and it is an evolution of the Broadbent Model. It operates similarly but it introduces the idea that we can shift our attention from one thing to another based on what's important. This model demonstrates how we can easily change our focus based on auditory or visual stimuli.

Dichotic vs. Selective Listening

Dichotic listening examines how we handle multiple sounds at the same time, while selective listening involves isolating and concentrating on specific sounds in noisy environments.

Auditory Selection

Auditory selection is the process that allows us to distinguish and focus on a specific sound while ignoring or blocking background noise. This process is essential to be able to understand and communicate in noisy environments.

Cocktail Party Effect

The Cocktail Party Effect is a good example of auditory selection. It commonly occurs in crowded or noisy environments, where individuals can concentrate on a specific conversation or sound, such as a person's voice, despite background noises. This phenomenon highlights how importance auditory selection is in enhancing our auditory experiences.

Types of dichotic listening tests

Voice onset manipulation

Voice onset manipulation involves changing the timing of auditory input, specifically when a voice or sound begins. For example, you can delay a voice relative to a background sound or vice versa. This method can be used to study how the brain perceives and processes auditory signals based on the timing of the sounds perceived.

Language Processing

Dichotic listening can be used to test for the hemispheric asymmetry of language processing and to understand whether there are significant differences in language lateralisation between individuals.

To understand this, let's explain "cerebral laterisation": The brain has two sides, the right and left hemispheres, which are connected by the corpus callosum. Each side does different things. Cerebral laterisation means some functions are more dominant on one side of the brain than the other.

Emotional Factors

Anxiety and stress can interfere with a person's ability to focus on hearing from a specific ear during a dichotic test due to the hyperactivation of the nervous system.

Neuroscience

Dichotic listening tests are used in neuroscience to study language lateralisation. These tests can help examine the brain structures involved language perception and its asymmetry.

Schizophrenia

During a dichotic listening test on people with different types of schizophrenia, researchers found that people with paranoid schizophrenia have a more dominant left side of the brain compared to others when it came to listening tasks.

Unveiling cognitive complexities

Dichotic listening is used in a wide range of fields, including but not limited to, psychology and neuroscience. Even with the new research and technology that has emerged over the year, these tests help us learn more about how the brain deals with and focuses on sounds.

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