Isolated words in infant-directed speech

The study in a sentence

This study found that babies pay more attention to isolated words in language input than they do to words in running speech.

It highlights the usefulness of isolated words for babies in their language development and word learning.

Mini-experiment: try it for yourself

Imagine you’re a small baby who hasn’t yet learned to talk.

  • When people around you speak, what do you hear?

It’s probably quite like listening to people speaking a language you don’t know.

  • If you don't know Gaelic, try listening for individual words in this video of Iain speaking Scottish Gaelic.
(source: Wikitongues)

The question

The first thing you may notice in the mini-experiment is that people don’t speak one word at a time. Speech comes out of our mouths in a continuous stream with few breaks between sounds. This makes it difficult to figure out where one word ends and another begins.

  • How do humans ever learn words under these conditions?

Language learners (whether they be adults or babies) learn more frequent words more easily. If you hear a word a lot, you’re more likely to remember it. Another thing that may make words easier to learn is to hear them in isolation (with silence either side). If you were learning English, you’d probably find it easier to figure out that “pizza” is a word if you heard it in (1) than in (2):

      1. What’s for tea? Pizza.
      2. I like pepperoni pizza for tea.

Key concept

In acquisition studies it is important to distinguish between input and intake.

  • Input is, at a minimum, all the language that is directed at the baby, so called Infant-directed Speech (IDS).

It is not necessarily the case, however, that a baby pays attention to everything they hear.

  • Intake refers to that part of the input that the child actually pays attention to, that is, takes in.

Some researchers have pointed out that isolated words are not very common in the input, and from this they conclude that isolated words cannot be important for learning.

  • This study shows that babies do pay attention to isolated words in the input to a greater extent than to words in running speech.
    • The relative scarcity of isolated words in the input is overcome by their disproportionate usefulness to the child in their early attempts at word learning.

Do babies remember words more easily when heard in isolation or in running speech?


How can we work out what babies do or don't remember?

The Head-Turn Preference procedure is a well-established method of measuring what babies and infants pay attention to. The video explains how the procedure works.

Look at this lovely dugong.

Look at this lovely pet. Dassie.

The answer

In order to focus on whether babies do in fact learn better from hearing isolated words than words in running speech, Keren-Portnoy, Vihman and Lindop Fisher adopted a different approach from previous experimental attempts.

Instead of exposing babies to target words in a "special" or lab setting, they designed a picture book and asked the caregiver to read the book to babies at home, twice a day for three weeks.

  • The book contained a number of unfamiliar animal names
    • e.g., dassie, dugong, fennec, pudu (these are real animal names!)

Some of the animal names were presented in isolation in the book and some in a sentence.

  • After three weeks, the children were brought to the lab and the researchers used the Head-Turn Preference procedure to see which words were more familiar.

The results of the Head-Turn Preference test showed that the babies remembered the names they had heard in isolation better than the names they heard in running speech.

  • Keren-Portnoy, Vihman and Lindop Fisher concluded from this that isolated words are disproportionately useful to the baby for language learning, especially in the earliest stages.

Classroom activities

Lead in task

What makes words in an unfamiliar language stand out?

Extension task

Research design for a book study

In more detail

A longer explanation of the research study

isolated words > IMD

Meet the authors

Tamar Keren-Portnoy & Marilyn Vihman and Robin Lindop Fisher.

Robin devised this study in a final year module for the BA in English Language and Linguistics at York, then worked as paid research assistant on the project. Robin is now a qualified Speech and Language Therapist practising in London.

Read the paper

Keren-Portnoy, T., Vihman, M., & Lindop Fisher, R. (2019). Do infants learn from isolated words? An ecological study. Language Learning and Development, 15(1), 47–63.