Posthypnotic suggestions are implanted messages that do not show their effects until later, often unconsciously. In hypnotherapy, desirable posthypnotic suggestions are used to subtly influence behavior or reactions, but surprising examples also occur in nature. This article shows how posthypnotic suggestions function in birds, animals and humans – and what this means for our understanding of hypnosis.
Of Splendor elves and posthypnotic suggestions
Hypnosis researchersand therapists just can’t get enough of scientific research results to prove the “authenticity” of hypnosis. Apparently, they and many patients and potential patients are not satisfied with the old adage, “First believe and then see.
And want explanations and hard evidence. By scientific proof, then, is meant primarily anything that has been demonstrated by scientific research methods. Preferably with neurological equipment like EEG, fMRI, MEG, fNIRS and lots of pretty pictures of glowing brain parts.
Sound as password – Yet there are other equally convincing phenomena in all parts of the world. How about the superb fairy-wren(malurus cyaneus). Australians call it superb fairy-wren).
This is a tiny Australian bird, about 10 grams, barely bigger than a sparrow, but with an ability that seems plucked straight out of a hypnosis study book.
Each elven female chooses her own tune during the breeding season, a series of tones that is not found exactly like this anywhere else in the repertoire. Mother elves sing this unique “incubation call” to their eggs during the last days of incubation. Time after time, she sings this motif, softly and endlessly, to her eggs. When the young hatch, it turns out that this motif was not a random song. It is a password. The young must imitate the tone in their begging call to get food. If they don’t, the parents don’t recognize them as their own offspring. For meerkats like cuckoo chicks, this is fatal: They live too short a time in the nest to learn the password. Some young chicks try through trial and error to imitate the call of the elf cub, but this is often unsuccessful and leads to starvation. The tune the mother imprinted on them in the egg determines life or death for the young birds. Not only the splendid elves have such a system.
In nature, we see more organisms in a prenatal or trance-like state receiving suggestions that later initiate automatic behavior. During warm conditions (26-29 degrees C.), zebra finches (taeniopygia guttata) whistle a heatcall or hitter call at the end of the breeding season. This is a specific high-frequency and rhythmic song. They also sometimes do this throughout the incubation and sometimes even nesting phase. Such a hitter call warns the embryo against heat and affects its development in various ways and instructs it to endure the heat.
How does it work?
Hypnosis scientists seeking evidence for the influence of acoustic signals on physical processes get a nice present from zebra finches. Such a heat call causes a process known as vocal panting. This is panting breathing in which the bird makes distinctive sounds. This helps it cool down.
Embryos that hear these heat calls adjust their developmental patterns. They generally grow slower and stay shorter in hot environments, which probably helps with thermoregulation in hot conditions
What happens at the cellular level?
Researchers even figured out what triggers the hitteroep at the cellular level. Among other things, they found that the mitochondria in red blood cells of chicks exposed embryonally to these calls were more efficient at producing ATP (Adenosine triphosphate is the main energy-carrying molecule in living cells), while generating less heat – at least at mild temperatures.
In extreme heat (e.g., a 44°C heat wave), this efficiency may actually drop, possibly protecting against harmful oxygen radicals.
Chicks exposed embryonally to the calls showed a lower H/L ratio (heterophilic-lymphocyte ratio) as adults That is an important indicator of stress or immune activity, and indicates less chronic stress – regardless of the season. They showed better heat tolerance, different nesting preferences (such as warmer locations) and differences in behavior including learning non-paternal song patterns,
Posthypnotic suggestion
With these two birds, in pure form, one sees “posthypnotic suggestion” in practice: a message is implanted in a state of receptivity, and executed only later, under specific circumstances.
Splendid elves and zebra finches use an acoustic way to suggest but there are also animals that receive suggestions through other senses in a prenatal or trance-like state to later direct automatic behavior.
Cuttlefish – squid-like animals – grow up in eggs that, over time, become transparent. From then on, even before hatching, the embryos can see the outside world, such as possible prey. Research shows that they actually process those visual stimuli. In one experiment, unborn cuttlefish were given a view of crabs from their eggs. After birth, they were given a choice between crab and shrimp. The animals that saw crabs from their eggs preferred them. The animals that had a view of only shrimp found them more attractive after birth. This proves that animals learn visually before birth. Other species learn in utero mainly through smell or taste, but these cuttlefish learned purely by looking. Since young cuttlefish must hunt independently immediately after hatching, this early learning would help them recognize prey faster. Mother cuttlefish probably lay their eggs in places where future food is already in sight. Frog larvae learn to recognize vibration patterns (sensation) in their eggs that later function as alarm signals. Bee larvae acquire a role assignment (worker or queen) with pheromones (scent) that determine their behavior for life
The Critical Factor and its absence
These embryos are imprinted with a key to behavior without criticism. They hear in their shell the message and accept it without resistance, without doubt, without selection. They have no “critical factor” yet, no inner gatekeeper asking, “Does this even matter? Should I believe this?” Everything that enters the scale is imprinted.
Dave Elman, an influential hypnosis researcher and therapist introduced the concept of the critical factor. He described it as a mental gatekeeper that critically evaluates all suggestions. When we are not in trance, that gatekeeper functions incessantly: he compares, weighs, questions. He protects us from direct influence. Hypnosis works by temporarily bypassing or weakening the critical factor so that suggestions can be implanted directly into the subconscious. Later, when the critical factor returns, the implanted suggestion can still be carried out. Often automatically, without understanding exactly why. This is the essence of post-hypnotic suggestion.
In the case of the splendor egg, this mechanism is radical. The embryos do not yet have a critical factor. They are an unwritten page, a fragile memory that stores everything delivered without defense. Whereas the hypnotherapist must circumvent the gatekeeper with artifice and inductions, nature does it more simply: there ís no gatekeeper yet. The melody is imprinted, and as soon as circumstances call for it, it echoes back.
In the egg, the splendid elf teaches his children a melody that will save their lives. Again and again we see the same ancient principle: a signal slips past the critical factor and settles directly into the unconscious, where it later comes to life automatically.
For the hypnotherapist, this is more than a curiosity. It is a reminder that words are not always the key. Sometimes sound, cadence or melody, in fact, opens the door to change. Sometimes the real power of suggestion lies not in what we say, but in how we make it sound. As the beauty elf proves: one tone sequence, repeated in silence, can last a lifetime.
The development of criticality: from womb to language
This leads to a question of crucial importance in hypnotherapy: how and when does that gatekeeper, that critical factor Dave Elman speaks of, develop in the human being? The answer is surprisingly clear: that critical factor does not yet exist in the prenatal phase. A fetus does have ears, eardrums, ossicles and primitive processing of sounds, but what is missing is the semantic network needed to recognize or reject meaning. In the womb, the child can absorb rhythm, intonation, melody and timbre, but it cannot distinguish between sense and nonsense, between a love poem and a shopping list. Everything comes in as sound. Everything resonates directly with the still unformed brain.
Therefore, it is not surprising that babies immediately recognize their mother’ s voice after birth. They turn their heads to that familiar sound, become soothed at the intonation that reached their ears through amniotic fluid for months. And the melody of the mother tongue is also imprinted prenatally: French babies cry in ascending melodies, German in descending ones – an effect that shows conclusively that the fetus does not learn words, but prosody: the music of language. Here, then, exactly the same mechanism works as in the splendor infant: a sound motif is imprinted before birth, which automatically evokes behavior after birth.
Stages of brain development
Hearing works from about 20 weeks, but the cortex (where language and abstract thought are processed) is far from mature. The fetus hears mostly intonation, rhythm, melody and timbre, but does not yet have a neural network to store concepts or rules. What sticks is emotion, sound pattern, voice recognition.
The young child, in the absence of neural network, also cannot make semantic links. Cognitive knowledge requires conceptualization: that a word refers to something, that a number, a quantity represents. In the womb, the fetus can distinguish sounds, but cannot link them to concrete referents or symbols. So you can build recognition (“this is mother’s voice, this is a familiar rhythm”), but not knowledge (“this is the letter A”).
What does happen: acoustic imprinting
Experiments show that after birth, babies have a preference for the language or melodies they often heard in the womb.
The first stages after birth
So in the first months of life, there is still no criticality. The child hears voices, melodies, rhythms, and it absorbs them without defense. There is no “no” yet, no “I don’t believe that” yet. Everything that sounds is experienced. The child recognizes patterns, but it does not question them.
Between the ages of zero and two, language acquisition begins. Words acquire referents: “mommy,” “ball,” “milk. For the first time, a timid gatekeeper appears. The child learns that not every sound is random; some sounds refer to something reflected in reality. With this, an ability to distinguish is cautiously growing. Yet this is not yet a critical factor in Elman’s sense: the child cannot yet reject suggestions on the basis of logic. It imitates, it accepts, it trusts.
The preschool phase
Only between the second and sixth years of life does the critical factor grow into something recognizable. Children learn to say “no. They ask questions, “Why? They begin to distinguish between fantasy and reality. They become receptive to stories, but they can also protest, “That’s not real! Here for the first time arises the ability to no longer let suggestions in blindly. The gatekeeper awakens.
This also explains why young children are so susceptible to hypnosis and play: the critical factor is not yet firm. Suggestions slip in easily. Where an adult would hesitate or resist, a child often responds immediately and without resistance.
The adult phase
Only with adult fluency does the critical factor fully mature. The adult hears a sentence and weighs up, “is this right, is it true, do I believe this? So here the hypnotist must use techniques to bypass the gatekeeper: relaxation, monotone repetition, shock, confusion or focused focus.
The splendor fairy does not have to do any of this. The fetus of the splendor fairy is offered the melody before there is anything to protest. The human fetus is offered the same thing: the voice of mother, the rhythm of language, the cadence of a lullaby. Only later does the gatekeeper come, only later does the possibility of resistance arise.
Learning in the belly? The illusion of prenatal learning
Yes, there are still people who talk or sing to a pregnant belly to explain grammar rules or recite arithmetic in the belief that this will give the child an advantage later.
Source: AI
The idea that a baby can learn in the womb has been around for centuries. In many cultures, expectant parents sing or talk to their unborn child, hoping thereby to form a bond or even stimulate development. In Japan, as early as the Edo period (17th-19th century), it emerged the concept of taikyō – fetal education that was based on the belief that the way a pregnant woman lived, ate, thought and felt directly affected the child in the womb. In the 20th century, this idea was further developed: women were advised to listen to beautiful music, look at art, read poetry and speak gently to the child to make it smarteror more sensitive. You can still find pregnancy magazines and courses around taikyō in Japan, advising reading aloud, talking softly to the belly, and playing music by Mozart or Japanese nursery rhymes.
Initially, it was about establishing a good bond with the child and making the child smarter or more sensitive. But in the 20th century, precisely in countries where there was an unhealthy rat race to get the best spots in the economy such as Japan and America, so-called prenatal education programs, such as Prenatal University(USA), were developed to teach babies cognitive knowledge, sequences or even sums even before birth. Even today, companies are capitalizing on this with more advanced techniques and devices such as BabyPlus, which offers rhythmic sounds to train the fetus’ learning ability. Parents are promised a cognitive “seed capital” for their child – to get a head start in school even before the first breath and later secure a better-paying job.
But acquiring school knowledge prenatally is not biologically possible.
Cognitive functions – such as memory, language comprehension or pattern recognition – require working brain networks, which do not begin to form somewhat until about week 28 and are not truly functional until after birth. The embryo or young fetus does not have the neural structures to process information, let alone store or understand it.
What can be done is sound recognition. Fetuses from about week 28 can distinguish certain sounds, such as the mother’s voice or rhythms of music. But this is not “learning” in the sense of building knowledge or skills. It involves primitive sensory perception, without awareness or understanding.
There is scientific evidence for recognition and bonding, but hardly any for actual knowledge transfer. ‘Scientific’ devices and courses that suggest this offer hope, but not science. A truly valuable start-up capital is given only after birth – with attention, care and love.
Reality is more prosaic. The fetus cannot learn algebra, cannot store a dictionary, cannot practice a foreign language. It lacks the necessary neurological infrastructure for that. What the fetus can do is record sounds, melodies and emotions. These are not school lessons, but posthypnotic suggestions: signals that are imprinted without a critical filter and later evoke recognition. So the fetus cannot learn English grammar, but it can get used to the melody of English. He cannot learn numbers, but he can memorize the intonation of number songs.
Parallel with hypnosis
For the hypnotherapist, this offers a wealth of insight. Dave Elman says the critical factor must be bypassed for a suggestion to be effective. The beauty elf and the human fetus show a stage when that factor does not yet exist. Then everything is open, then everything penetrates.
Cognitive knowledge, symbols, logic – those come only once the critical factor develops. Those are always subject to its censorship. Therefore, school knowledge will never be able to be imprinted prenatally. But sound, rhythm, melody, intonation – those have a free pass. Those slip in unimpeded. That means the therapist must work outside the realm of pure semantics. Sometimes the form is more powerful than the content. Sometimes it is the melody, the repetition, the cadence, that disarms the gatekeeper and plants the suggestion. As with the fetus. As with the beauty elf.
The critical factor develops with the language, not before the language. In the womb, there is no censor, only resonance. Therefore, an unborn child can remember a melody and associate it with the safe feeling in the womb. That is why a chick in the egg cannot gain knowledge of the world to come but can imbibe its mother’s call. And this is why the hypnotherapist can teach that the path to the unconscious often does not pass through words, but through sound, through rhythm, through music.
Why the ‘school dream’ doesn’t work
Hypnotherapists can do a good job of explaining to parents who want to give their unborn child words or sums why that won’t work. That there is confusion because a fetus hears sounds but cannot yet process language or meaning. Symbolic thinking – necessary for arithmetic or language comprehension – only develops after birth, as the brain continues to mature. In hypnotherapy, we know that impressions without a critical factor (as in hypnosis or prenatal experience) do come in, but only affective signals: sound, rhythm, emotional tone. Cognitive knowledge requires an inner “gatekeeper” – and there simply isn’t one yet. So expectant parents must be convinced what does work: loving voice, quietness, repetition. What does not work: imposing school knowledge on a brain that is not yet ready for it.
The critical factor develops with language; before language there is no censor, only open resonance for sound. This is why an unborn child cannot learn algebra, but can memorize the melody of the mother’s voice as a lifelong password.
The hypnotherapy of the Wonderful Fairy
In this regard, Gibbons’ growth metaphor of the bird hatching from the egg is an interesting starting point to incorporate the example of the splendid elf. This example text by Gibbons can be found in the book by Cladder and Lens (1985):
Verbatim:
“…Now imagine that you are a very small bird about to crawl out of the egg. Hold that image in your imagination and concentrate on it…
And the sense of reality, of it really being so will grow larger and stronger with every second that passes, and it won’t be long before you can experience everything I am describing. It is a beautiful spring day outside, and through the thin shell of the egg that encloses you, you can hear the sound of the wind in the tree, and around your nest, and you can hear other birds singing happily, as if inviting you to come out and share with them in the celebration of life…
You are a little bird in its egg, ready to peck its way out. Let yourself fully experience that event and all that comes with it. Feel how cramped you are trapped there in that egg, and feel how the urge to break out grows bigger and stronger with every second. The insistent life forces within you can no longer be ignored.
The shell that has been your enclosure until now is no longer able to hold you back. You must break through it, heading for the world that awaits you, for the forces of life and growth are growing stronger, pressing in more and more with each passing moment.
You now begin to pick your way through the shell, slowly at first, but then with faster and faster movements…. And the scale begins to crack and give way under your persistent efforts…. A small piece is already breaking off…. And you see a glimpse of the delightful world beyond…. It is a fantastic and captivating world of a beauty that makes you feel even stronger and even happier, so that you redouble your efforts to break out…
More and more pieces of the shell are falling away and you can now push your head all the way through the hole you have made…. And with effort of all your young forces you force a crack along the whole length of the egg…. And the crack gets bigger and bigger as you push and wriggle…. Until finally the shell breaks in two and you stand with a sense of triumph on the threshold of a new life. You are completely free from all the constraints of the past Freed from everything that has held you back…. You are ready to enter a new phase of your life, ready to unfold and use all the new talents and abilities that have quietly developed, right there inside that shell.
As you stand there on the threshold of a new existence, you can feel the vibrations of a song rising within you…. A song of victory, a song of happiness, of growth and strength, of celebration of life…. And as you spread your wings for the first time, you feel the chords erupting brightly and powerfully…
Hear the song in your head…. And listen how it blends with the singing of the birds around you (20″ pause)…. And the images now fade away, you become more and more aware again of yourself and the person you are…, but the feelings of triumph and happiness will stay with you…. And you will be able to keep what you have learned with this experience with you…. And each time you practice this experience, the feelings of power and triumph and happiness will grow stronger and greater, while at the same time its positive effects on your daily life will increase just as much…”
What is striking is that Gibbons is only beginning where the splendidelfling has already finished her work. She has imprinted the posthypnotic suggestion – how to get food later – well before the hatchling breaks out of the egg. Prior to that, Gibbons bird – also still in the egg – should also be given suggestions that it can take advantage of later.
Possible addition to Gibbons’ growth metaphor:
Now imagine that you are a very small bird that will soon hatch. Hold that image in your imagination and concentrate on it…. And the sense of reality, of it really being so, will grow larger and stronger with each passing second, and it won’t be long before you can experience everything I describe.
Before you are even aware of your own wings or existence outside, something extraordinary happens. You are still inside an egg. Closed, safe, in silence. But through that shell a voice is already sounding – clear, rhythmic, full of expectation. It is your mother’s voice, whispering something to you. Not words, but a melody that repeats itself. Sometimes soft like a bell, sometimes shrill like a whistle.
You can’t understand it yet, but you hear it. You hear it again and again, until you begin to feel that it means something. Not because you think it does, but because it awakens something in your body. Something that becomes focused, calibrated, attuned. To unfold and be able to use all the talents and capacities you need. Now you realize what talents and capacities those are and that they are growing in you now.
It is like being called, not to come now, but to know later what to look out for. To then use your new talents. As if that sound already gives you a direction – an expectation, a tone to tune into. And as you grow there in the darkness, something else also grows within you: an answer, a memory, a recognition.
Only then – when everything in you is made ready by that repeated signal – comes the moment when you begin to move, to push, to look for a way out.
And that’s where your story begins….
© Johan Eland, 2025
Resources
Cladder, J.M. & Lens, J.W.M. (1985). Modern hypnotherapy: a textbook for psychotherapists. Lisse: Swets & Zeitlinger.
Gibbons, D.E., Applied hypnosis and hyperempiria, Plenum 1979
Learn more about posthypnotic suggestion and criticality?
What is a critical factor in hypnotherapy?
In hypnotherapy, the critical factor is the inner gatekeeper that evaluates and usually filters suggestions. During hypnosis it is temporarily bypassed, allowing acceptable suggestions to be recorded directly in the unconscious. This explains how posthypnotic suggestions later, under the right circumstances, manifest naturally.
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