Preservation of primary phonetic and acoustic cues of phonemes trigger their perceptual identification. Time reversal of speech both preserves and alters phonetic and acoustic features of speech signals. Invariant features such the power spectra of a signal are usually maintained whilst properties such as duration and the shape of the temporal envelope, as well as finer details of the acoustic spectrum are altered (Grataloup, Hoen, Veuillet, Collet, Pellegrino and Meunier, 2009). Non-continuant speech sounds are more susceptible to altered perception in reversals as assymetry typically occurs in the shape of the temporal envelope. This is the case in stop bursts, abrupt vowel onsets, and ramping (smooth increase in amplitude) and damping (smooth decay) of signals (Pellegrino, Ferragne and Meunier, 2010). Time reversal of these features alter the characteristics of the speech signal, permitting perception of alternative phonemes, and even the addition of phonemes to the speech signal, or the omission of phonemes from the forward speech.

One study has been conducted that investigates the preservation of phonetic cues in time reversed speech and the perception of reversed phonemes. Pellegrino, Ferragne and Meunier (2010) conducted an experiment which required four phoneticians to listen to pseudowords that were recorded and played in reverse, and phonemically transcribe what they heard. The results of the study showed that around 25% of the original segments from the forward speech were exactly retrieved in reverse. The experiment also demonstrated that certain phoneme types were more likely to be distinguished than others. Fricatives (e.g. /f, v/) liquids (e.g. /l/) and nasals (e.g. /n, m/) were identified at a rate above 90%, and vowels at close to 90%. The authors suggest that the high rate of identification likely reflects the invariance of continuant waveforms preserving a high level of perceptual cues permitting perception. Rhotics (e.g. /r/) and voiced stops (e.g. /b, d, g/) were identified at an intermediate level (66.7% and 61.8% respectively). Listeners, however, were inaccurate with unvoiced stops (e.g. /p, k, t/), with a rate of only 9.4%, as well as schwas (mid central neutral vowel /ə/).

The ones that were not correctly recognised were identified as phonemes having alternative place and/or manner of articulation. 30% of unvoiced stops were transcribed as fricatives. 25% were identified as stops, which also included other stop types such as glottal stops or unreleased voiced stops. 28% were heard as a cluster; for example, a final /t/ in the natural speech was heard as an /sn/ cluster. The authors suggest that the /n/ arose from the ramping of the vowel in the time-reversal signal. 7% were transcribed as a sonorant (r, l, m, n, w, y) while 10% of the stop segments were not detected.

The findings of this study suggest that not only are speech sounds from the forward speech heard in reverse, sounds that are not in the forward speech are also perceived as phonemes.

These perceptions are typical in Reverse Speech. Although many phonemes from the forward speech are perceived, others are heard as alternative sounds, and this is certainly the case with unvoiced stops. They can be perceived as a phoneme with a different place of articulation (e.g. /t/ → /k/ or different manner of articulation (e.g. /t/ →/s/, /p/ → /f/). An alveolar stop and alveolar /l/ can convert into another alveolar consonant; for example, /t/ or /d/ may be perceived as /n/ or vice versa. Others may be heard as allophones (different variation of the one phoneme; e.g. /t/ → /ʔ/ or unreleased /t/), or a similar phoneme such as an alveolar tap /ɾ/. Phoneme addition can occur such as /t/→ /st/. Stop bursts can disappear when reversed, lost in the vowel sound that came before it in reverse, resulting in perception of an alternative phoneme, an unreleased allophone, or omission altogether. Omission of sounds from the forward speech is a common occurrence. Light articulation of consonants or the strong frication of vowels next to a consonant may result in non-recognition of the consonant.

Some sounds in time reversed speech are highly ambiguous and may be heard differently by different listeners. Alteration of phonemic cues through reversing or degrading of the sound through audio noise or poor audio quality contribute to ambiguity. In this case, one’s grammatical and lexical knowledge comes into play in phoneme selection, projecting the desired phoneme to produce meaning.

Reverse Speech is very much about the perception of speech sounds and finding meaning though the building of strings of language that make some grammatical and syntactical sense. But of course, this is very much the case for normal speech as well. We turn the sounds uttered by another into coherent meaning. When listening to speech, we cannot actually perceive each individual speech sound. We assume that they are there. However, if we were to examine the individual segments of spontaneous forward speech, we would find that not all phonemes of the heard words are recognisable; they may sound different or be missing altogether. Yet, there is ample remaining of the speech signal to perceive a coherent string of words. The rest is projected into it.

So, we can now see that Reverse Speech is composed of perceivable phonemes and segments. Not covered by Pellegrino et al. is whether the segments produce lexical information. It can be easily proven that they indeed do. However, to perceive strings of language correctly, one needs to operate within linguistic possibilities and parameters. This entails examination of phonemes and segments of reversed speech as well as comparing them to the information in the forward speech. This means understanding linguistic processes. This also means knowing that some speech sounds in forward speech can be heard differently to the sounds which normally make up words.  It is important to know what is wrong with the string of words just as it is important to know what is right. This helps to set reasonable linguistic parameters for what can be accepted as linguistically viable. There are innumerable examples out there in ‘Reverse Speech World’ that are obviously not what they are claimed to say. There are also many that can sound like what they are attested to be, yet still lack the necessary evidence for it.

Yet, strings do occur that mirror acceptable language. Nevertheless, proving that they are anything but coincidental is another matter. Every day, there are perhaps trillions of strings of language produced by speakers around the world. Quite naturally, ‘words’ will appear that are purely coincidental, even if they are a grammatically acceptable string of two, three or four words which are composed of perhaps one or two content words and one or two particles. One can shake these in front of linguistics all day and get a response like “that’s interesting, but no cigar!”, even if they did seem to have some meaning regarding the speaker and what he was saying. For attention to be garnered, linguistically viable strings that are much longer need to occur; say, a minimum of 7 words in length with ample examples of ones that are more than 10 words and even as long as 15 -20 words.

Funnily enough, they exist.


Grataloup, C., Hoen, M., Veuillet, E., Collet, L., Pellegrino, F & Meunier, F. (2009). Speech Restoration: An Interactive Process, Journal of Speech, Language, and Hearing Research, 52, 827-838.
Pellegrino, F., Ferragne, E., & Meunier, F. (2010). 2010, a speech oddity: Phonetic transcription of reversed speech. Interspeech 2010, 1221 – 1224.

Byrne and Normand. (2000). The Demon-Haunted Sentence: A Skeptical Analysis of Reverse Speech

The authors make claims that can lead readers to believe that David Oates is a shyster, fraudently profiteering from his claims. For example:

  • ‘His company … is dedicated to profiting from his discovery’.
  • A ‘reviewer’ of David Oates’ book, Susan Brombacher, concluded ‘that (Oates) seems more interested in making a profit than educating others.
  • ‘The Reverse Speech Web page contains a plethora of merchandise and services available to consumers at considerable prices’.
  • ‘ ….. those who pay (David Oates) a hefty sum and go through his training can then serve as expert witnesses and command hefty sums themselves’.

It is my suggestion that researchers like Byrne and Normand drop the fact that David Oates makes an income from Reverse Speech, and avoid the urge to use this as a method to discredit the man and the phenomenon.

The attention given to the fact that Reverse Speech is an income-producing enterprise takes away from the necessary argument concerning its genuineness, appears as small-mindedness, and smacks of academic ‘poor form’.  They would do well in ascertaining whether real speech exists, and what it is that is producing it.

The authors write:

“The person trained to hear reverse messages could intentionally or unintentionally report that speech contains hidden incriminating evidence. Many people are not prepared to refute such contrived evidence”.

The authors state that the potential for harm is enormous if Reverse Speech is accepted in places such as a court of law. I agree that it is problematic. It is easy to err without sound skills. This goes for any use of Reverse Speech. A certain perceived stress pattern and the existence of some phonemes can cause the listener to hear a phrase even though other phonemes are incorrect, ambiguous or missing. The ambiguities can mean that it lacks evidence as the documented reversal, and could easily be heard as something else, or nothing at all. Of course, in normal speech, all kinds of processes occur – phoneme assimilations, elision, dropped phonemes and so on – one needs to work with a knowledge of language and its processes and what might be viable within a reasonable set of limitations. After an informed analysis leads the analyser to believe that the reversal indeed represents the sounds of language, it needs to be ascertained whether it is genuine unconscious language rather than just coincidental language-like sounds. Next, what/who the language refers to would have to be identified through a cogent interpretation. What aspect of the person is the ‘voice’? Is it an aspect that represents normal conscious thinking or how he/she views events and those around them? Or is it a denied aspect of the self? Or is it an aspect that communicates at a deeper, more profound level? When the voice uses personal pronouns, such as ‘I’, ‘he’ and ‘you’, who is this entity referring to? Is it the speaker himself or a third person, and if so, who is that third person?  Does the reversal refer directly to the spoken forward speech, or is it the indirect result of a trigger from the forward speech, and refer instead to events or memories of the further past?

The authors apply to Reverse Speech circumstances and conditions which can result in misunderstood and misinterpreted language. For example, they refer to B.F. Skinner’s verbal summator. The authors state:

“The verbal summator consisted of a phonograph (or tape) of random vowel sounds that were grouped together in such a way as to not produce any systematic phonetic groupings. These random phonetic sounds were arranged into patterns that approximated common stress patterns in everyday conversation’.

After such strings of nonsense syllables were arranged, they were played for subjects at barely audible volume levels. After repeatedly listening to these sounds, subjects reported “hearing” the phonograph or the tape “say” things. These sentences, or sentence fragments, did not actually exist and, as such, were considered to be utterances that were already strong in the subject’s repertoire. Put another way, they were “projecting” their own thoughts onto the sounds they were hearing”.

The authors go on to add, “phonemes may sound similar to a meaningful phrase but are really sound salad’. A listener expecting to hear a certain phrase will likely do so”.

Quite true, we project into the signal to hear language, and even more so when there are issues of low audibility, background noise, or audio noise occurring. Masking effects cause the listener to hear a particular utterance that is not there. However, it is not only in Reverse Speech that this can occur; it also occurs in normal speech. Projection into sounds and priming or prompting are issues that affect the hearing of speech whether it is forward or backward. However, Reverse Speech is at a distinct disadvantage compared to normal speech. Here is why:

  • When listening to normal speech, we know it is real language (unless someone has played a trick and recorded noises from a dog that mirror a human stress pattern, and used masking noise over it!). With Reverse Speech, speech needs to be identified from non-speech. This means recognising what sounds reasonably constitute language. It also means being able to recognise a structure that sounds like language as being genuine or simply coincidental.
  • The analyst needs to identify the beginning and the end of the reversal. Identifying only some of it can alter how it is interpreted overall, or it can result in completely different words due to how it has been ‘cut’ from a longer utterance. The same thing would occur in normal speech.
  • People are not used to hearing Reverse Speech and, much like hearing an accent or language style one is not used to, it can lead to difficulties in comprehension.
  • We do not understand the mechanisms by which it occurs.

These issues do not mean that Reverse Speech is not a real phenomenon. But it does mean that there are considerable challenges associated with it – many of the difficulties that can occur with normal speech in a comparable situation. Because of the inherent challenges of Reverse Speech, those who investigate it ought to possess appropriate linguistic skills.

In reference to papers such as Byrne and Normand, I suggest that anyone who seeks to offer a critique of the existence of Reverse Speech, do so by first identifying whether there are grammatically-acceptable, linguistically-viable utterances in reverse that are significant in number. I have yet to see a critical study that addresses this basic first point of consideration. From the recognition of the large number of utterances in reverse which are of interest linguistically, one then needs to show whether they are simply coincidental sounds and have nothing to do with  some level of consciousness. An honest appraisal of the not-insignificant amount of material available that is arguably linguistically-viable, as well as grammatically and syntactically acceptable, should then lead to the question of whether an act of intelligence/awareness can or does produce it. Of course, we are unable to demonstrate scientific evidence of this at this time. Nevertheless, psychology has increasingly become more comfortable with the existence of the unconscious and the subpersonalities that act upon the person. Of course, it is quite a jump to a consideration of the unconscious aspects of a person communicating via the reversed sounds of the speaker. Perhaps in time, further understanding of the mysteries of the brain and the unconscious will lead toward more consideration of the phenomenon.

Byrne, T & Normand, M. (2000). The demon-haunted sentence: A skeptical analysis of Reverse Speech. Skeptical Inquirer (24)2. Retrieved from haunted_sentence_a_skeptical_analysis_of_reverse_speech1

Recently I have been examining speech reversals on the internet. It is clear that there is a plethora of examples that are ambiguous or obviously incorrect. Clearly, projection is occurring. Yet, some responders on the various sites indicate agreement with examples while others oppose. I have to assume that concurrence with highly dubious reversals is a case of priming which Mark Newbrooke claimed was a factor in hearing reversals. This is where the words are given to the listener beforehand, and this influences the listener’s perception. The listener perceives a syllable count, hears some phonemes or allophonic variations that are within linguistic limits, and the remainder is projected into; the mind adds the necessary sounds, and/or deletes others so that a recognisable string of language occurs. Furthermore, there are many reversals that are of 2 to 5 words, Out of the multitudinous strings of speech occurring each day, it is not unreasonable to expect short language-like strings from the reversed sounds that are simply coincidental occurrences. 

So, projection occurs; priming occurs, too. Short strings of speech are not all that remarkable – often they are just the reverse of the sounds of the forward speech, and probably occur when different people say it, or there are a couple of ambiguous sounds that allows the mind to fill in the ‘right’ sounds. But, with all that said, does this mean that there is nothing genuine about reversed speech? Not necessarily. It means projection is an issue. It means that there are plenty of poor or ‘shaky’ examples around. 

Amongst all the valueless apparent language, there is some pretty powerful stuff, and stuff that occurs in much longer strings of language, that I believe, are reasonably there within linguistic bounds. It is these longer strings that ‘separate the men from the boys’ so to speak. 

This is why I continue to look at Reverse Speech.

This study, published in 1993, chiefly looked at the effect of reversals on listeners, and is motivated by previous claims of influence of backward messages in rock music. It does not address Reverse Speech.

In the study, the authors played backward messages to one group and the forward speech content to another group. Afterwards, to both groups, the backward speech examples were played along with other examples which were not in the original examples. Their findings showed that the group that listened to the backward speech were able to recognise more of the actual backward speech played again to them than the ones that heard only the forward speech. As expected in the study, those who heard backward messages were able to recognise more than those who heard the forward speech of the backward examples played again. Acoustics (backward message group) were recognised more than meaning (forward speech group).

A second part to the study had groups read forward speech examples and decide whether they were what they had heard. The forward speech group recognised more of the speech than the backward speech group.This, of course, is understandable. Asking people to recognise the forward speech behind backward speech examples of a set of examples they heard once is asking their conscious mind to recognise something supposedly subconscious, soon after hearing. The conscious mind gets in the way, of course. The subconscious is sub … conscious. Play forward speech statements and then ask a group to recognise typed statements they had heard … well, how significant will the result be compared to the other group? Tests of this sort are only really worthwhile through a longer term observation of behavioural change through the influence of the subconscious. Yet, even then, those who listened to the backward speech recognised the forward statements at a proportion of 0.53 compared to the forward speech listeners at a proportion of 0.55, which is not a great difference.

In any consideration of Reverse Speech, there is little that is particularly informative here – the effect of reversals on the non-speaker listener is of interest, of course; however it is secondary to the consideration of whether real speech occurs, and what this means for the speaker himself. Secondly, asking the conscious mind to simply recognise what the subconscious is supposed to recognise, is just as likely to produce error, and, therefore, having those who heard forward speech and then seeing the typed forward speech, will, naturally, have an outcome greater than one who did not hear it. Thirdly, in Reverse Speech, intelligible language occurs in both modes. This study refers to forward speech played in reverse as gibberish.

A further point – the authors note that subjects were inexperienced at listening to backward speech. They suggested that people who were skilled at converting forward speech into backward speech (and vice versa?) could be good candidates for detection of backward messages. Of course, consciously-aware conversions have little to do with subconscious influences of messages. Again, there is nothing in this that has value in any consideration of Reverse Speech.

Prompted language

The authors state, “the target may be missed many times unless listeners are warned to listen for it”. This is an argument brought up by other researchers such as Newbrook and Curtain (1997) – that suggestion prompts hearing. Their point is quite correct –  suggestion can and does manipulate what people hear/believe etc. And, in regard to listening to backward messages, there is validity in the claim. However, it becomes a case of this can happen, therefore in all situations and cases it can be nothing more than suggestion.

The authors put forward the premise that potential meaning is there, but actualised meaning is not unless it can be heard by the listener. So, for meaning to be actualised, it must be decoded by a listener; therefore, if a listener fails to decode it, then there is no meaning. On the other hand, meaning is simply potential unless there is a listener with the right skill/ability can decode it, such as in understanding a foreign language. Their implication seems to be that, unless listeners can pick up messages independently, free from prompting, the message remains potential, and not actualised; in other words it may not be there at all. A message, then, may not be heard as something easily comprehensible,  and it would require either a particular decoding skill, or someone pointing out that it is there, aka suggestion.

Surely, if a backward message that approximates language is played, it stands to reason that more people will hear the message if pointed out than if not indicated. A study by Thorne and Himelstein (1984) found that 18% of listeners who were told to listen for messages in rock music (but not specifically satanic messages) heard satanic words, while 41% who were told to listen for satanic messages heard them. Of course, people will not always pick up short snippets of language that appear suddenly and unannounced, and that are not well enunciated – if two or three words from rock music, or from fast, casual speech were played amongst gibberish, surely more will pick up language that has been first indicated?

So, yes, there is no argument that people are influenced by verbal suggestion. Yet, if one played short segments of backward messages amongst gibberish, it is understandable that people will be more likely to recognise it if prompted. This, quite frankly, may be found to be true for forward speech. Play rock music or fast casual speech as short snippets of three to six words, and place it amongst gibberish, which group will hear significantly more? The prompted or unprompted group? The fact that more will hear speech that is prompted than unprompted does not ‘prove’ the lack of existence of backward messages. In addition, it must be realised that backward speech is not exactly the same as forward speech. Although many linguistic processes are shared by both modes, backward speech has its own nuances that occur through the subconscious communicating at the same time and space as the conscious speaker. People are not used to hearing speech in its backward mode. Just as people do not hear some accents as well as others, people will be less likely to pick up speech easily (and unprompted) that can be different to what they are used to hearing.

There are three questions that inform my thinking about Reverse Speech.

The first question is, are there substantial amounts of grammatically acceptable, linguistically-viable language in the reverse of speech? The answer is yes, there is. This can be proven. The next question is, can this language inform us about the person? The answer is yes, it does appear so. There is substantial evidence that is contextually/person-relevant (although I admit this can also be a product of projection and wrongful interpretation). The next question is, who/what is producing this language, what is the situation actually referred to, and, who does the message refer to? Any worthwhile interpretation would, and needs depend upon which subconscious aspect is communicating (if one is to differentiate aspects rather than see the subconscious as a single entity), and the actual situation/experience referred to, and who the referent is.

Begg, I. M., Needham, D. R., & Bookbinder, M. (1993). Do backward message unconsciously affect listeners? No. Canadian Journal of Experimental Psychology, 47(1).

Newbrook, M., & Curtain, J. (1997 ). Oates’ theory of Reverse Speech: a critical examination. The Skeptic (17)3

Thorne, S.B., & Himelstein, P. (1984). The role of suggestion in the perception of satanic messages in rock-and-roll recordings. Journal of Psychology (116), 245-248