Auditory Illusions: How Our Brains Can Be Fooled

An illusion is an inaccurate perception of a stimulus. The term is also broadly used to refer to inaccurate beliefs or perceptions. Illusions provide powerful clues about how the brain processes information. Scientifically, they can pose a problem for empirical research as they demonstrate the ways in which even direct observation can be misleading.

Humans are fairly susceptible to illusions, despite an innate ability to process complex stimuli. Confirmation bias is believed to be largely responsible for the inaccurate judgments that people make when evaluating information, given that humans typically interpret and recall information that appeals to their own biases. Amongst these misinterpretations, known as illusions, falls the category of auditory illusions.

The Nature of Illusions

Illusions can occur with any of the five senses. Here's a breakdown:

Optical illusions: These may be seen when an image is constructed in such a way that it relays misleading information to the brain. Most people can be tricked by optical illusions, and scientists can use information about this visual phenomenon to better understand perception and brain organization.
Auditory illusions: These occur when a person hears sounds that are not actually being made or sounds that are distortions of the actual tones.
Tactile illusions: These cause the brain to perceive touch stimuli that is not actually present, or that is not present in the way the brain perceives it.
Smell and taste illusions: These are not as common as other types of illusions. However, certain people may perceive smells differently than others do, especially when given conflicting information about the stimuli producing the smell.

Illusions are different from hallucinations in that hallucinations occur without an external stimuli. Like hallucinations, though, illusions are not necessarily a sign of a psychiatric condition, and anyone might experience them. They can occur for many reasons, such as the effect of light on an object, insufficient sensory information about an object, or errors in an individual’s processing of sensory details. Certain illusions, known as pseudohallucinations, can be signs of a psychiatric disturbance. One may experience a pseudohallucination under conditions of anxiety or fear or when he or she projects their feelings onto external objects or people. People in intensive psychiatric care have been reported to see people around them as monsters or devils, for example.

Synesthesia is a particular type of illusory phenomenon where individuals experience certain sounds as colors. A musician might see green when he or she hears a particular piece of music, for example. Some writers have also reported hearing musical tones when they see a particular word or image.

Auditory Illusions Explained

Auditory illusions highlight areas where the human ear and brain, as organic survival tools, differentiate from perfect audio receptors; this shows that it is possible for a human being to hear something that is not there and be able to react to the sound they supposedly heard. Many auditory illusions, particularly of music and of speech, result from hearing sound patterns that are highly probable, even though they are heard incorrectly. This is due to the influence of our knowledge and experience of many sounds we have heard.

In order to prevent hearing echo created by perceiving multiple sounds coming from different spaces, the human auditory system relates the sounds as being from one source. However, that does not prevent people from being fooled by auditory illusions. Sounds that are found in words are called embedded sounds, and these sounds are the cause of some auditory illusions.

Spatial information is processed with greater detail and accuracy in vision than in hearing. Composers have long been using the spatial components of music to alter the overall sound experienced by the listener. One of the more common methods of sound synthesis is the use of combination tones.

Examples of Auditory Illusions

There are a multitude of examples out in the world of auditory illusions.

One example is number 5 - ‘Virtual Barbershop’ features a session at the barber’s and is stupendous when listened to on headphones. The final seconds are great! You hear someone say “green needle” one moment and “brainstorm” the next-depending on what you expect to hear.

Another example is number 7 (‘Falling Bells’): ‘This is a recording of a paradox where bells sound as if they are falling through space. As they fall their pitch seems to be getting lower, but in fact the pitch gets higher. If you loop this sample you will clearly see the pitch jump back down when the sample repeats.

Some of them are illusions that are like visual illusions. But perhaps the most striking examples are only an illusion in the way perspective is a visual illusion - you can perceive something in 3-D that’s only really in 2-D. Hear (!) you perceive something in space, when it’s just in your head. These are examples of ‘dummy head’ recording.

Auditory Illusions and Silence

"We typically think of our sense of hearing as being concerned with sounds. But silence, whatever it is, is not a sound-it's the absence of sound," said lead author Rui Zhe Goh, a Johns Hopkins University graduate student in philosophy and psychology.

The team adapted well-known auditory illusions to create versions in which the sounds of the original illusions were replaced by moments of silence. For example, one illusion made a sound seem much longer than it really was.

"Philosophers have long debated whether silence is something we can literally perceive, but there hasn't been a scientific study aimed directly at this question," said Chaz Firestone, an assistant professor of psychological and brain sciences who directs the Johns Hopkins Perception & Mind Laboratory. "Our approach was to ask whether our brains treat silences the way they treat sounds. Like optical illusions that trick what people see, auditory illusions can make people hear periods of time as being longer or shorter than they actually are.

In tests involving 1,000 participants, the team swapped the sounds in the one-is-more illusion with moments of silence, reworking the auditory illusion into what they dubbed the one-silence-is-more illusion. They found the same results: People thought one long moment of silence was longer than two short moments of silence.

Participants were asked to listen to soundscapes that simulated the din of busy restaurants, markets, and train stations. They then listened for periods within those audio tracks when all sound stopped abruptly, creating brief silences.

The idea wasn't simply that these silences made people experience illusions, the researchers said. "There's at least one thing that we hear that isn't a sound, and that's the silence that happens when sounds go away," said co-author Ian Phillips, a Bloomberg Distinguished Professor of Philosophy and Psychological and Brain Sciences. The researchers plan to keep exploring the extent to which people hear silence, including whether we hear silences that are not preceded by sound.

Auditory Illusions in Learning and Development

"What learners hear isn’t always what they learn. Auditory illusions show us that expectations shape perception-which means training can unintentionally mislead if we’re not careful. L&D professionals must design learning experiences that reinforce clarity, support multiple learning styles, and ensure key messages aren’t lost in interpretation." - Dr.

Common Mistakes in Learning Design:

The Mistake: Relying only on spoken instruction without supporting materials.
The Mistake: Using jargon, vague terms, or phrases that can be easily misinterpreted.
The Mistake: Assuming all learners process spoken information equally.

Solutions:

Try This: Ask learners to explain a key concept without using specific terminology.

Conditions That Affect the Brain

Some conditions that affect the brain may also cause illusions. Auditory illusions can also be caused by a small lesion in the right medial geniculate body.

Table of Illusions

Type of Illusion	Description	Example
Optical Illusion	Misleading visual information	The Müller-Lyer illusion
Auditory Illusion	Hearing sounds that aren't there or distorted tones	The McGurk effect
Tactile Illusion	Perceiving touch stimuli inaccurately	The phantom limb syndrome
Smell Illusion	Perceiving smells differently than others	Smelling non-existent odors
Taste Illusion	Experiencing tastes that are not actually present	Tasting sweetness with certain medications