Priming, in relation to speech, is the tendency of the human ear to hear words that have been suggested, either explicitly or by context – even though there may little or no acoustic evidence for those words.
The power of priming has been very well known in phonetics at least since the 1950s. Here we describe one classic experiment often cited as a demonstration of how priming works.
The experiment was carried out in 1958 by Donald BRUCE of Reading University, England. Bruce first prepared a number of sentences of roughly similar type. Here are two examples.
- Sentence 1
I tell you that our team will win the cup next year.
- Sentence 2
You said it would rain but the sun has come out now.
He then prepared an acoustic ‘mask’ of white noise (a strong hissing sound) at a level such that when the sentences were played through the mask, most people heard around 25% of the words.
The intention of his experiment was to show what happened when listeners were primed with a keyword that gave a context for the sentence (e.g. SPORT for Sentence 1; WEATHER for Sentence 2). He expected that priming listeners with these keywords would help them to hear more of each sentence through the same degree of masking noise – and indeed he did convincingly demonstrate that (now unsurprising) fact.
However, he also found something far more interesting. What happened when he presented a misleading keyword (e.g. WEATHER for Sentence 1; SPORT for Sentence 2)?
One might expect this would enable listeners hear fewer words, or to hear them with less confidence – but that is not what happens. Rather than hindering perception, a misleading prime helps listeners just as much as relevant one – but it ‘helps’ them hear the wrong sentence.
Here are some examples of how listeners heard Sentence 1 with misleading keywords.
- Sentence 1 (FOOD)
I tell you that I feel more hungry than you do.
I tell you that our food with be something to do with beer.
- Sentence 1 (TRAVEL)
I tell you that I too will leave next year.
I’m telling you that I have seen New Zealand.
- Sentence 1 (HEALTH)
I tell you that our team has been free from injury all this year.
- Sentence 1 (WEATHER)
I tell you that I see the wind in the south next year.
Most surprisingly of all, listeners heard the incorrect sentences (with misleading primes) just as confidently as they heard the correct sentences (with appropriate primes).
The most important thing about priming is that people typically have no idea they have been primed. As with many aspects of human cognition, hearers ascribe their perception to the stimulus, ignoring the contribution of their own minds. That is why it is so dangerous to leave evaluation of forensic transcriptions to the jury.
For a recent demonstration of just how dangerous it can be, see The Crisis Call Experiment.
- Bruce, Donald J. “The Effect of Listeners’ Anticipations on the Intelligibility of Heard Speech.” Language and Speech: 79–97.
- Fraser, Helen. 2003. “Issues in Transcription: Factors Affecting the Reliability of Transcripts as Evidence in Legal Cases.” International Journal of Speech Language and the Law 10 (2): 203–226.