Can speech illusions happen spontaneously?

Yes. Speech illusions can happen spontaneously.

As a matter of fact, they usually happen almost entirely unplanned.

There is still lots of ongoing research into this phenomenon.

What are speech illusions?

Speech illusions are a type of auditory illusion that gives a person the impression that they have heard a certain speech phrase when something else was spoken.

There may be a few known speech illusions discovered that can be a basis for understanding the way we perceive language.

What Causes it to happen?

When the acoustic sounds of the human voice are produced in an unclear way, it usually happens.

Yet different words are clear enough to be distinguished.

When speech illusions happen in everyday life

The physical environment that we find ourselves in can sometimes cause illusions to be heard.

Listening to the speech sounds of the Quintina is an example of auditory illusions that can be found in everyday life.

Factors such as the shape and size of the walls around us can contribute to the hearing of unintended sounds.

As well as the vocal sounds being produced.

What parts of words makes illusions possible

All the frequencies, intonations, rhythms, vocal strength, etc., of the human voice makes speech illusions possible.

Every aspect plays a part in the overall sound output that we hear.

So, changes to any part of sounds produced may have a drastic effect in what words we perceive.

Psycholinguistics and speech perception

Psycholinguistics is the field of study that deals with the human speech perception system.

To understand psycholinguistics is to understand the creation of speech illusions.

A lot of the spoken words we hear in such a phenomenon depends on the categorization of associated phonation.  

Auditory illusions from spoken words

A combination of specific acoustic speech sounds produced, along with our primed perception of words heard, causes audio illusions to happen.

For example, the simple care / said he doh care speech illusion illustrates this.

It is fascinating to observe the various ways that we can perceive speech.

Conclusion

It appears that we may not always notice where and when these things happen.

We take it for granted that we can truly trust our ears to give us an accurate assessment of the sounds we hear.

When it is quite possible for us to be deceived.

There is so much more to be learnt from such human experience.

The more chances we have at studying these occurrences, the better we would be at dissecting the hidden world.