Researchers have attached cameras to babies to develop a new theory of infant language-learning.

Their new study suggests that a baby's most likely first words are based upon their visual experience.

The team from Indiana University says the number of times an object enters an infant's field of vision “tips the scales” in favour of associating certain words with certain objects.

“Visual memory may be the initial key to getting words stuck on objects - familiar visual objects like table, shirt, bottle or spoon,” said Dr Linda Smith, a neuroscience researcher.

“It's an aggregated experience; those very first words may be learned - slowly and incrementally - for a few visually pervasive objects. This may be how infants begin to break into language before their first birthday.”

Although many researchers have studied infants' first words to understand learning, Smith said none have approached the question from the visual side.

“While studying language acquisition from the 'word side' may benefit those studying later stages of language learning - at the ages of 18 months to 3 years - it cannot account for how children break into language,” she said.

Under the new theory, which Smith and colleagues call the ‘Pervasiveness Hypothesis’, a few highly prevalent objects stand out to infants among the “clutter” of other less frequent objects to become their first words.

The researchers analysed videos from head-mounted cameras set up to show the visual field of eight children - five girls and three boys - between 8 and 10 months old, the period before children engage in verbal interactions with parents and caregivers.

The children wore the cameras for an average of 4.4 hours. Caregivers were told the cameras would observe children’s daily activities, not words or objects specifically, and could choose when to activate the camera.

For the purpose of the study, researchers observed mealtime scenes, defined as any eating by anyone at any time or location - in cars, at playtime or in a high chair, for example.

The recordings contained 917,207 mealtime frames, so researchers sampled one from every five seconds. Five objects were recorded for each frame: a total of 745 objects.

The researchers then divided the named objects into “first nouns”, which are acquired by half of all 16-month-olds, “early nouns”, which are known by half of all 30-month-olds, and “late nouns”, which are acquired at later stages of learning.

First nouns include words such as table, shirt, chair, bowl, cup, bottle, food, spoon and plate.

The study's results revealed a strong correlation between the most frequently appearing objects and “first nouns”, with the top 15 of these words appearing in the images collected by the study.

“The comparison of first and early nouns was particularly striking, since both sets of object names are acquired quite early in childhood and refer to objects common in households with infants,” said Elizabeth Clerkin, a Ph.D. student in the unversity’s Bloomington Department of Psychological and Brain Sciences and first author on the study.

“That infants' visual environment during mealtime consistently involves a very small number of objects - and the names of these high-frequency objects are among those normally learned first by infants - suggests visual experience is doing the heavy lifting in very early word learning,” she added.

Whether children who experience speech disorders are not picking up visual regularities in the environment or simply live in households with fewer regularities, Smith said it's vital to explore the role of both words and vision in language learning.

“Taking account of the visual brings a whole new dimension of word-learning into view,” she said.

“If all you ever worry about is the word side of word-learning, you may be missing half the problem: visual cues that aid language learning.”