Babies Learn The Sounds of Their Language

We mentioned that part of what makes learning language difficult is that languages carve up sounds and different Ianguages carve them up differently. A wide variety of different sounds, with very different spectrograms, will all seem like the same sound to us, and, in turn, that sound will seem sharply different from other sounds that are actually quite similar to it physically. Suppose you use a speech synthesizer to gradually and continuously change one particular feature of a sound, such as the consonant sound r, and play that gradually changing sound for people. You very gradually and continuously change the r sound to /. What is actually coming into the listeners' ears is a sequence of sounds, each of which is just slightly different from the last. But what they perceive is someone saying the same sound, r, over and over, and then suddenly switching to a new sound, /, over and over. The listeners have divided up the continuous signal into two sharply defined categories: either it's an r or an I, not anything in between. They can't distinguish between all the different r's. even though the sounds themselves are quite different. Scientists call this categorical perception, because a continuously changing set of sounds is perceived categorically as being either black or white, r or /, with nothing in between.

The way we categorically perceive speech is unique to each language. In English we make a sharp categorical distinction between rand Z sounds. Japanese speakers don't. In fact,Japanese speakers can't hear the distinction between American r and /, even when they are listening very hard. (Hence all the dubious jokes about Japanese speakers ordering what sounds like "flied lice" instead of "fried rice.") Pat was in Japan to test Japanese adults and their babies on the r-/distinction. She had carefully carried the computer disk with the rand /sounds to Japan, and when she arrived in the laboratory in Tokyo, she played them on an expensive Yamaha loudspeaker. She thought that such clearly produced sounds would surely be distinguished by her Japanese colleagues, who were quite good English speakers as well as being professional speech scientists. As the words rake, rake, rake began to play out of the loudspeaker, Pat was relieved to know that the disk worked and the sound was perfect. Then the train of words changed to an equally clear lake, lake, lake, and Pat and her American assistant smiled, looking expectantly at her Japanese colleagues. They were still anxiously straining to hear when the sound would change. The shift from rake to lake had completely passed them by. Pat tried it over and over again, to no avail.

When a language does not make a clear distinction between two sounds, the children of that language cannot hear the distinction in other languages.