What is the effect of gradual increase of speech speed on speech comprehension?

Question

When I am watching a YouTube video with normal speed I can understand everything with no problem. When I speed up the video to 1.25x my understanding of what someone is saying is a bit worse, but after 1-2 minutes it is very clear again.

I have made an experiment in which I was increasing the video speed gradually to 2x (in ~5 minutes) and I was understanding everything very good. After some time I started the same video again, but then I switched it directly from 1x to 2x and I still could understand what someone is saying in the video, but it was worse than in gradual speed increase.

Why is this happening?

Answer 1

The ability to understand speech at increased voice rates is all about learning. A notable example in this regard is the use of text-to-speech software like Jaws used by blind folks unable to read the written word. Jaws is able to convert text on screen into the spoken word using a speech generator. After people get used to read on-screen content through speech, they are often able (and happy) to increase the voice rate settings to scan over the (often cluttered) computer screens more quickly. A recommended incremental step for Jaws in speech rate is 5%. I have experienced the speech rates deployed by some blind folks and the resulting speech was totally unintelligible to me.

With regard to the learning curve you describe: I bet that after repeated exposure to higher speech rate settings you wouldn't feel the necessity to start at a slower pace. Assuming you have normal vision, you are probably not too inclined to practice this for hours, though.