Dominic Stone
Humans have ear muscles, but they are considered vestigial, meaning they are evolutionary remnants that once served a purpose but no longer do. These muscles were once used by our primate ancestors to move their ears and funnel sound. While they are now obsolete, they still activate when we listen intently, and some people can even wiggle their ears. These muscles are the subject of ongoing research, as they may provide an objective measure of listening effort and have implications for hearing aid technology.
| Characteristics | Values |
|---|---|
| Purpose | To move the pinna to capture sounds |
| Use | Activate when listening closely to something |
| Function | Pull the ears up, forward, and backward |
| Reflex Action | Still exists |
| Muscle Activity | Could provide an objective measure of listening effort |
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What You'll Learn
- Humans have vestigial ear muscles that activate when listening intently
- Superior auricular muscles are the largest of the three extrinsic ear muscles
- The auricle contributes to our ability to localise sounds
- The auricularis posterior muscle is linked to the facial muscles that pull the mouth into a smile
- Ear muscles may be useful for psychologists seeking an objective way to measure emotion
Humans have vestigial ear muscles that activate when listening intently
Humans have several vestigial muscles, including those around the ear. Vestigial organs or muscles are those that have become functionless through the course of evolution. In the case of the ear muscles, they once helped our primate ancestors to move their ears to funnel sound and improve their hearing. However, over time, humans became much more proficient with their visual and vocal systems, and the pressure to move the ears for better hearing decreased. As a result, these ear muscles are now considered vestigial, with little practical use in modern humans.
Despite their vestigial nature, recent studies have found that these ear muscles do exhibit some activity when listening intently. In a study conducted at Saarland University in Germany, scientists attached electrodes to the sides of participants' heads and asked them to listen to an audiobook while facing different levels of difficulty and distractions. The results showed that the more challenging it was for participants to hear the audiobook, the more the superior auricular muscles activated. This suggests that even though humans cannot physically move their ears to focus on a sound, these vestigial ear muscles still activate as if trying to "prick up their ears".
The activation of these vestigial ear muscles during challenging listening tasks indicates that they may be engaged as part of an attentional effort mechanism. This discovery could provide an objective measure of listening effort, which may be useful for hearing aid technology. For example, a hearing aid could monitor the activity of these muscles and adjust its settings accordingly to improve the user's listening experience.
Furthermore, the study of these vestigial ear muscles and their response to sound can provide valuable insights into auditory attention and the evolution of the human auditory system. By understanding how these ancient muscles functioned in our ancestors, researchers can gain clues about hearing deficits in infants and the development of the human brain. Additionally, the discovery of vestigial traits in humans highlights the evolutionary footprints that provide insight into our species' history and development.
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Superior auricular muscles are the largest of the three extrinsic ear muscles
The superior auricular muscle is the largest of the three extrinsic ear muscles. These muscles are located around the ear and are made up of two sets: the extrinsic and the intrinsic. The extrinsic muscles, which include the superior auricular muscle, connect the ear to the skull and scalp and move the ear as a whole. The intrinsic muscles, on the other hand, extend from one part of the ear to another.
The superior auricular muscle is found above the auricle of the outer ear. It originates from the epicranial aponeurosis and inserts into the upper part of the medial surface of the auricle, drawing it upwards. This muscle is thin and fan-shaped, with fibres that converge to be inserted by a thin, flattened tendon. It is supplied by the temporal branch of the facial nerve (VII).
Research has shown that the superior auricular muscle exhibits increased activity during effortful listening tasks. This suggests that this muscle is engaged not merely as a reflex but potentially as part of an attentional effort mechanism, especially in challenging auditory environments. When participants in a study were asked to listen to an audiobook with different levels of difficulty, it was found that the superior auricular muscles activated more during the difficult mode than the easy mode.
The superior auricular muscle is considered vestigial in humans, as humans lost the ability to move their ears about 25 million years ago. However, it is believed that these muscles still activate when people listen intently, almost like a reflex to "prick up its ears". This activation may be so minuscule that it provides no perceivable benefit. Nevertheless, the activity of the superior auricular muscles could provide an objective measure of listening effort.
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The auricle contributes to our ability to localise sounds
The auricle, or pinna, is the visible portion of the outer ear. It collects sound waves and channels them into the ear canal, where the sound is amplified. The auricle contributes to our ability to localise sounds.
Sound localisation is a listener's ability to identify the location or origin of a detected sound in direction and distance. The human auditory system uses several cues for sound source localisation, including time difference and level difference (or intensity difference) between the ears, and spectral information. The ears being on different sides of the head results in differences in the sound signals between the two ears. These differences are known as Interaural Time Difference (ITD) and Interaural Intensity Difference (IID). The duplex theory, presented by Lord Rayleigh in 1907, explains that the distance between the acoustic source and the ears results in a propagation delay between the two ears, which generates the ITD. The human head and ears may also have a shadowing effect on high-frequency signals, which results in the IID.
The auricle plays a role in sound localisation by collecting sound waves and directing them into the ear canal. The shape of the auricle, or pinna, also influences the way sound waves bounce off and enter the ear canal. This is known as the shadow effect and is one of the cues used by the auditory system for sound localisation.
In addition to the auricle's role in sound localisation, there is also evidence that the auricular muscles may contribute to our ability to localise sounds. These muscles exhibit increased activity during effortful listening tasks, particularly the superior auricular muscle. When participants in a study were trying to pay attention to sound coming from a speaker behind them, the posterior auricular muscle showed electrical activity, as if attempting to point the ears in that direction. This suggests that the auricular muscles may be involved in moving the pinna to capture sounds, similar to the way animals move their ears to localise sounds.
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The auricularis posterior muscle is linked to the facial muscles that pull the mouth into a smile
The auricularis posterior muscle is one of the three large muscles that connect the auricle to the skull and scalp. It is innervated by the branches of the facial nerve and is supplied by the posterior auricular branch and artery. This muscle draws the auricle of the outer ear backward, and while the effect is usually very slight, some people can wiggle their ears due to more significant movement in this muscle.
The auricularis posterior muscle is considered a vestigial muscle in humans, meaning that it has lost most of its functionality over time. However, research suggests that it still plays a role in monitoring sounds we cannot see. When we listen intently, the auricularis posterior muscle activates, and the ear moves slightly in the direction of the sound source. This movement is an attempt to prick up its ears and improve hearing, similar to the way animals move their ears to capture sounds.
The facial muscles that pull the mouth into a smile include the risorius, levator anguli oris, zygomaticus major, and zygomaticus minor. These muscles work together to elevate the angles of the lips and pull the mouth laterally and superiorly, resulting in a smile.
While the auricularis posterior muscle is not directly involved in smiling, it is linked to the facial muscles through the facial nerve (CN VII). The facial nerve has posterior auricular branches that supply the auricularis posterior muscle, as well as the occipitalis muscle, part of the occipitofrontalis muscle, and some intrinsic ear muscles. The facial nerve also innervates the risorius and levator anguli oris muscles, which are directly responsible for forming a smile.
Therefore, while the auricularis posterior muscle itself does not pull the mouth into a smile, its connection to the facial nerve and its role in auditory attention could indirectly influence the activation of the facial muscles involved in smiling.
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Ear muscles may be useful for psychologists seeking an objective way to measure emotion
Human ears cannot prick up, but vestigial ear muscles do activate when listening intently to something. These muscles, which once allowed our evolutionary ancestors to pivot their ears, are now too weak to move our ears. However, they still exhibit electrical activity when we engage in challenging auditory tasks.
The superior auricular muscle, for example, exhibits increased activity during effortful listening. This suggests that it is engaged as part of an attentional effort mechanism, especially in difficult listening environments. The auricularis posterior muscle, on the other hand, responds most strongly when people are happy, for reasons that are not yet understood.
The activation of these ear muscles may be useful for psychologists seeking an objective way to measure emotion and listening effort. Currently, the primary method for measuring listening effort is monitoring pupil dilation, but this technique is challenging to implement in the real world. Muscle responses, on the other hand, cannot be faked, making them a more reliable indicator of emotional state than self-reported emotion questionnaires, which can be inaccurate if people lie or are unaware of their emotions.
Additionally, the existence of vestigial ear muscles contradicts the notion of intelligent design, as they serve no apparent purpose in humans. This discovery provides new evidence supporting the theory of evolution and the process of natural selection.
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Frequently asked questions
Ear muscles were once used to move our ears to funnel sound. Today, they are vestigial, meaning they are remnants of evolution that once had a purpose but no longer do. However, recent studies have found that they activate when people listen intently.
To test whether humans still use ear muscles, scientists attached electrodes to the sides of people’s heads and asked them to listen to an audiobook. The audiobook was played at different volumes and with other competing sounds. The scientists found that the more difficult it was for participants to hear the audiobook, the more the ear muscles activated.
These findings suggest that the activity of the ear muscles could provide an objective measure of listening effort. This could be useful for hearing aid devices, which could monitor the activity of these muscles and adjust the volume accordingly.
Humans have many intrinsic ear muscles, despite the human ear’s limited movement compared to other mammals. Some people can also wiggle their ears, which is controlled by the same muscles that once allowed our evolutionary ancestors to pivot their ears.
The three large muscles that connect the ear to the skull and scalp are the superior auricular muscle, the anterior auricular muscle, and the posterior auricular muscle.
