Word prediction

Also called Predictive text, Prediction, Next-word prediction, Word completion

The device guessing your next word. It can halve the keystrokes or double the effort, and there is a way to tell which it is doing.

What it is

Word prediction is the row of guesses a device offers while a person types: type "th" and it offers "the", "that", "there"; finish "I want" and it offers "to", "a", "some". Select the guess and the whole word goes onto the sentence strip in one hit. Most text-based AAC has it, and so does every phone keyboard.

Some systems also predict the next symbol on a grid, and some learn the person's own words and phrases and start offering those.

Who it can help

People for whom each selection is expensive: switch scanners, eye-gaze users, anyone with slow or effortful movement. For them a prediction that saves five letters saves real seconds and real fatigue. People who spell approximately, since a prediction can rescue a word that was started wrong. And people with word-finding difficulties, who recognise the word they wanted when it appears.

It is not free. Every prediction has to be read, judged and either taken or ignored, and for a fast typist, or a person who reads slowly, that is more work than typing the letters. Children learning to spell may lean on it before they can spell, which is fine for talking and bad for literacy unless someone is teaching the spelling separately.

How it works

The device keeps a dictionary ranked by frequency, and usually a second one of the person's own usage, and after each keystroke it lists the most likely completions and next words. Settings control how many guesses appear (three to six is typical), where they sit, whether they are spoken on hover for auditory scanning, and whether the person's own words are learned. Learning is what makes prediction personal: after a month the first guess after "my" is the name of the person's dog.

Whether it helps is measurable. Time a message with prediction on and off, and count selections. If the person is faster or less tired with it on, keep it; if they are slower because they are reading the guesses, turn it off or reduce the number.

Getting started

Do the test. Pick five sentences the person says often, and time them with prediction on and then off. Ask the person which they preferred. Let the answer decide.

Tune rather than toggle. Fewer guesses, larger text and predictions placed nearest the keyboard all cut the reading cost.

Check what it has learned. A prediction dictionary that has absorbed a week of a teenager's messages will offer those words to their gran; most systems let you clear or edit the learned list, and someone should know how.

Where to get help

CALL Scotland publishes clear guidance on prediction settings and their effect on rate. ACE Centre covers it in its literacy and access resources. A speech and language therapist or the specialised AAC service that set the device up can adjust and measure it with the person.