26/10/2025

Music alters Perceptual Identity Judgement

Perceptual Identity Judgement

One of the basic questions that our brains have to answer is:

For example, if I see a person this morning, and then I see a person this afternoon, did I see the same person?

Depending on the exact circumstances and any relation that I might have with that person (or people), it might be quite important for me to know whether or not it was the same person.

This is an example of sequential perceptual identity judgement, ie across perceptions happening at different times.

We can also consider simultaneous perceptual identify judgement, in relation to different perceptions happening at the same time. For example, if I see movement and I hear a sound, were those perceptions of the same event?

Music: an Altered State of Mind

Our subjective experience of music is consistent with the idea that music creates an altered state of mind.

But what exactly is it that gets altered?

We can observe that music does affect us, in some way, but it is hard to pin down what exactly these different scenarios have in common.

Is there some single principle that underlies all the different effects that music has on us? Or are there different things going on?

Hypothesis: Perceptual Identity Judgement

I propose a hypothesis about the altered state of mind induced by music, which is:

There is a secondary hypothesis about how this happens, which is:

Sequential Identity

Our notions of sequential identity are generally based on observed continuity and presumed uniqueness and permanence.

Our understanding of how the same thing can be perceived differently at different times usually includes some concept of motion, be it motion of the observer or motion of the thing being observed.

I see a red vase on a table. I walk up to the table and walk around it, looking at the vase. As I move around the vase, what my eyes actually see changes, but my brain perceives it as the “same” vase the whole time.

I might watch as someone else picks up the vase and moves it around, but my brain still determines that it is the same vase.

If I go away and come back the next day, and see a red vase, I might assume by default that it is just the same vase (although it’s entirely possible that someone else switched it with a different vase when I wasn’t looking).

Technical note: Different Perceptions of the Same Thing

Before giving specific examples of how this hypothesis applies to specific features of music (and to features of other things that often accompany music), it is worth thinking about what is normally involved when we experience different perceptions of something that our brains consider to be just the one thing.

A vase is an example of a rigid 3D object. Our perception of 3D objects is based on 2D projections that form images on each of our retinas. Our brain processes these images to derive its perception of the object. The 2D projected images are a function of the object’s orientation in space, how far away it is, and what direction the observer is looking. Other factors that affect the visual appearance of an object include lighting conditions and whether or not it is partially hidden behind something else.

In the case of something more complicated, like a person, there are also internal degrees of freedom, starting with all the different ways that a person can use their muscles to change position or posture, or to be in motion.

But in both cases (vase or person) we can abstract the idea of a “thing” being something that has permanent characteristics of some kind that distinguish it from all other “things”. It’s an abstraction in the sense that all perceptions of one “thing” are represented by the concept of that thing being what it is.

Examples

I will now list some aspects of music where a group of perceptions occur either simultaneously or sequentially, and where:

  1. they might be considered to be perceptions of different things, or,
  2. they might be considered to be different perceptions of the same thing.

(According to my primary hypothesis, the musicality of music causes these perceptions to be interpreted as perceptions of a single thing, and not as separate perceptions of different things, ie option 2.)

Melodic Phrases

A melody might consist of a sequence of melodic phrases, for example there might be four phrases, which have some similarity to each other, but are also different.

Chord Sequences

A tune might have an underlying repeated chord sequence, like Am F C G (ie A minor, F major, C major, G major).

Melody harmonies

A song might be sung simultaneously by three singers, where one singer sings the main melody, and the other two singers each sing a different harmonisation of that melody.

Synchronized Dancing

We can also consider examples of things accompanied by music.

For example, there are three hip-hop dancers doing synchronized dance moves to a song – that is they are all doing the same dance moves.

Exact Repetition

I have given examples of major components of a musical item where I hypothesize that music causes the perception of different components as actually being, in some way, perception of the same thing.

But what actually drives this willingness to unify the perception of apparently different things?

I have previously proposed that exact repetition plays a significant role in determining the musical quality of music.

Most of the exact repetition that occurs in music is the repetition of the smallest low-level components of music, such as note pitches, note intervals, harmonic frequencies (ie within a given note), beat intervals and regular beat periods.

I propose this hypothesis:

(Note: there is of course some exact repetition of high-level components in music, for example, some of the extended melodic phrases in a melody may be exactly repeated. The point of the hypothesis is that the exact repetition of low-level components causes the brain to consider high-level components to be repetitions of the “same thing”, whether or not they are directly perceived as exact repetitions. So some of the musical phrases in a sequence might be actual exact repetitions, but the brain wants to consider all of the musical phrases to be repetitions of something that is the “same”.)

We can regard exact repetition of low-level components as providing a type of “evidence” that the higher-level components are themselves repetitions of something, where the nature of that “something” has to be determined by the brain based on the actual different perceptions it receives of that supposedly unique something.

I will give a simple example based a very simple musical melody consisting of a sequence of musical phrases.

We can start by considering a situation where a melodic phrase actually is exactly repeated. For example, condider a phrase consisting of notes C D E, which is repeated 3 times:

Because the phrase is exactly repeated, it follows that the individual notes are exactly repeated, ie C occurs 3 times, D occurs 3 times and E occurs 3 times.

If we apply the logic in the converse direction, we can regard the exact repetition of the individual notes as evidence that the large 3-note phrase is itself exactly repeated.

We can also consider the pattern of scale steps occurring within each phrase, which will be:

(ie 1 step up from C to D and 1 step up from D to E - note that I am considering “steps” here, and not actual intervals, ie tone steps, and you will soon see why).

Now let’s consider a different melody, with three different phrases:

Here the actual phrases are no longer exact repetitions.

However exact repetition of individual notes still occurs:

Also, we can consider the pattern of scale steps occurring within each phrase, and that is actually the same as before:

(Here you will note that it is the “same” because I am considering “steps” as being the same whether or not they are tone steps or semitone steps.)

Thus, based on the occurrence of this amount of exact repetition, we still have “evidence” that the melody consists of a repetition of the “same” thing, and if we accept this evidence, then we could conclude that the listener’s perception of the three melodic phrases actually consists of three different perceptions of that same thing.

Of course we can see that this evidence is somewhat spurious – for example the note E is repeated, but it actually occurs in a different position within each musical phrase. So the observation that E repeats is not really proof that those phrases are the same.

What I propose is that the brain has a mechanism for determining the likely repetition of high-level components based on the amount of repetition observed in low-level components, and that mechanism is lossy in the sense that it just measures the overall amount of repetition in the low-level components, and it loses information about exactly where that repetition occurs and how that relates from one high-level component to the next, and therefore it cannot determine if the actual pattern of repetition logically implies that the high-level components are being exactly repeated.

One possible explanation of how such a lossy mechanism could work is that it is implemented via glial cells (ie non-neuronal brain cells), where there are glial cells that “observe” the behaviour of associated neurons, and they output a non-specific signal that indicates the overall level of exact repetition occurring, and neurons elsewhere read that signal to then determine the degree to which they should assume that somewhat different perceptions are actually perceptions of the same thing.

Such a mechanism is lossy because information about the occurrence of different exact repetition events is combined into just one signal that is broadcast non-specifically and received by a large number of recipient neurons, and in the process of combining and broadcasting that information, the details of what was exactly repeated when and where are lost.

Other Examples

Chord Sequences

Consider a chord sequence Am, F, C, G as mentioned above.

If we expand each chord into its component notes, we have:

We can see that there is quite a lot of exact repetition within the low-level components:

Notes within a Chord

If we consider the notes within a consonant chord, for example C major = CEG, there is repetition of individual harmonic frequencies within the notes (subject to the approximation that in a justly tuned scale the harmonic intervals don’t exactly match the corresponding intervals between notes):

What About Song Lyrics?

I have already mentioned synchronized dancing as an example of how the hypothesis applies to something that typically accompanies music.

But one thing that accompanies music and musical melody more than anything else is lyrics.

So I need to consider how this hypothesis would apply to the perception of song lyrics.

Lyrics are written in natural language, and they are almost always syntactically valid.

They can be more or less semantically cohesive, and they are mostly somewhat comprehensible if read (or heard) in a non-musical context.

So song lyrics are quite similar to spoken language in at least some respects, and this strongly implies that at least some portion of how the brain processes lyrics and speech is the same in each case.

However, most song lyrics are not the sort of thing that one would say in a normal conversation – so there is some significant difference between song lyrics and normal spoken language, and this presumably is a consequence of how the perception of song lyrics is not the same as the perception of normal spoken language, and presumably that is a consequence of the fact that song lyrics are embedded in music, and therefore the music is affecting that perceptual process in some manner.

So, does the hypothesis about exact repetition of low-level components apply to song lyrics?

There is one type of exact repetition that does indeed occur very consistently in song lyrics, that does not occur in normal conversational speech, and that is rhyming.

Rhyming is exact repetition in the straightforward sense that some of the sounds of words are repeated exactly, even though the words themselves are not being repeated.

Applying the “evidence” logic described above, the implication is that the listener’s perceptions of different lines of song lyrics constitute the perception of the “same thing”, that is, in some sense, it is as if each line of a song lyric is saying the same thing about something.

If the perception of song lyrics works this way, then it is significantly different to the perception of normal spoken language, because in normal conversation, each new thing that someone says is expected to be new information, and therefore definitely not the “same thing” as anything said previously.

Context Progression

Normal conversation consists of a sequence of utterances by one or more people.

Each thing said is understood by the listeners in the context of what has already been said, where each listener’s brain has to maintain a representation of the context.

Each thing said then changes the context from what it was previously so that the context itself includes that thing that was just said.

The previous context will still be relevant, but at the same time the brain has to make room for new context based on the newest part of the conversation.

We could assume that the existing context is subject to a constant rate of “fade”, so that the brain is not attempting to forever maintain all of the past context, but at the same time nothing gets suddenly removed from the context.

The rate of “fade” might itself be subject to some kind of control, perhaps as a function of the rate of speech of the speaker, or the listener’s expectations about the information density of the current speaker’s normal speech.

The difference with song lyrics is that if every line in a song is in some sense saying the “same thing”, then there is less need for context fade, because instead of constantly progressing, the context is just converging to a representation of whatever it is that the song is repeatedly saying.

So in summary, we can tentatively propose this hypothesis:

Story-Telling vs Paint-a-Picture Lyrics

Many song lyrics do fall into the “paint a picture” category, where the lyrics are effectively painting a picture, and each line or pair of lines is like a stroke of the paint brush that makes the picture clearer.

But there are song lyrics that have a more narrative structure, and those lyrics do tell some kind of story.

Necessarily a story involves an evolving context, so context progression does, presumably, happen in the listener’s mind as they listen to the song and understand the story.

Of course even narratives can contain portions of text that are doing some picture painting, as opposed to specifically advancing a plot line. So an amended version of the hypothesis could be that the effect of music on song lyrics doesn’t absolutely prohibit narrative story-telling with context progression, but that music more actively supports those parts of the story text that are in picture-painting mode, where context progression is at least temporarily suspended while in that mode.