Your own voice can change your ears
For most people it is quite easy to think of a person who always talks very fast, or someone who is a very slow talker. "This natural speed at which people speak is called habitual speech rate", says Bosker.
Speakers typically differ in their habitual speech rate and this can depend, for example, on age, extraversion, or regional background. At the same time, people are also capable of varying their speech rate, such as slowing down when speaking in public, or speeding up when conversing with friends.
Considering all this variation in speech rate, it is quite astounding that our ears (and the brain attached to them) seem to have little trouble understanding speech produced at different rates. One trick that listeners use to overcome rate variation in speech is to adjust sounds for the speech rate in their surroundings. In a recent study, published in the Journal of Experimental Psychology: Learning, Memory, and Cognition, Bosker showed in several experiments that perception of speech rate is influenced by the speech rate in the surrounding context, even if you produced that speech context yourself.
The same sound in different contexts
In one of the experiments, participants heard slow and fast sentences, followed by target words that were ambiguous between containing a short ’a’ and a long ‘aa’, such as tak (branch) vs. taak (task). "The ambiguous vowel was not quite as short as an ’a’, not quite as long as an ‘aa’, but kind of in between", Bosker explains. The participants’ task was to indicate which sentence-final target word they heard (e.g., "tak" or "taak"?). If the ambiguous ‘a/aa’ word was preceded by a fast sentence, participants responded that it sounded more like a word with a long ‘aa’. "In simple words: relative to the short sounds in the fast sentence, the ambiguous sound stood out as relatively long", says Bosker. Similarly, if the ambiguous word was preceded by a slow sentence, participants reported hearing more short ’a’ words.
My speech rate, your speech rate
In daily life, speech occurs most of the time in natural conversations where your own speech and the speech of your conversational partner are intermixed. In fact, on average, the silent gap in between the speech from two talkers is only roughly 100 milliseconds long. This means that another person's speech is heard in the context of your own speech. Now, can your own speech rate influence how you perceive the speech produced by someone else?
How we speak affects our perception
Another experiment in Bosker's study addressed this question. In that experiment, participants were instructed to produce sentences at a pre-specified fast and slow speech rate themselves. Immediately after each sentence they produced, the same ambiguous ‘a/aa’ words from the earlier experiment were played to them, and they had to indicate whether they heard “tak” or “taak”. Interestingly, participants’ perception of the ambiguous vowels also depended on their own preceding speech rate. That is, "they were more likely to report that they heard a long ‘aa’ word, if they had been talking at a fast speech rate only moments before", Bosker explains.
This study is the first to show that characteristics of our own voice (here: speech rate) can influence what we perceive others to say.
Bosker, H. R. (2017). How our own speech rate influences our perception of others. Journal of Experimental Psychology: Learning, Memory, and Cognition. Advance online publication. doi:10.1037/xlm0000381