New research published in Psychological Science, a journal of the Association for Psychological Science, examines the nuanced relationship between language and different types of perception.

Bilingual Infants Can Tell Unfamiliar Languages Apart

Speaking more than one language can improve our ability to control our behavior and focus our attention, recent research has shown. But are there any advantages for bilingual children before they can speak in full sentences? We know that bilingual children can tell if a person is speaking one of their native languages or the other, even when there is no sound, by watching the speaker’s mouth for visual cues. But Núria Sebastián-Gallés of Universitat Pompeu Fabra and colleagues wanted to know whether bilingual infants could also do this with two unfamiliar languages. They studied 8-month-old infants, half of whom lived in either Spanish- or Catalan-speaking households and half of whom lived in Spanish-Catalan bilingual households. The researchers looked at whether the infants could discriminate between English and French, two unfamiliar languages, using only visual cues. They found that the bilingual infants could tell the difference between the two languages, while the infants who lived in single-language households could not. These findings suggest that infants who are immersed in bilingual environments are more sensitive to the differences in visual cues associated with the sounds of various languages.

Lead author: Núria Sebastián-Gallés

Skilled Deaf Readers Have an Enhanced Perceptual Span in Reading

Though people born deaf are better able to use information from peripheral vision than those who can hear, they have a harder time learning to read. Researchers have proposed that the extra information coming in could distract from, rather than enhance, the process of reading. But no research has actually compared visual attention in reading between hearing and deaf readers.  In a new study, Nathalie Bélanger of the University of California, San Diego and colleagues investigated this issue by measuring the perceptual span, or the number of letter spaces used when reading, of skilled deaf readers, less-skilled deaf readers, and hearing readers. The experimenters manipulated the number of letter spaces that the participants saw while reading text on a screen. They found that, compared to the other two groups, skilled deaf readers read fastest when they were given the largest number of letter spaces, showing that they had the largest perceptual span. Regardless, they were able to read just as fast as skilled hearing readers. Contrary to previous hypotheses, these findings suggest that enhanced visual attention and perceptual span are not the cause of reading difficulties common among deaf individuals.

Lead author: Nathalie N. Bélanger

Stem Cells Turn Hearing Back On

Scientists have enabled deaf gerbils to hear again—with the help of transplanted cells that develop into nerves that can transmit auditory information from the ears to the brain. The advance, reported in Nature, could be the basis for a therapy to treat various kinds of hearing loss.

In humans, deafness is most often caused by damage to inner ear hair cells—so named because they sport hairlike cilia that bend when they encounter vibrations from sound waves—or by damage to the neurons that transmit that information to the brain. When the hair cells are damaged, those associated spiral ganglion neurons often begin to degenerate from lack of use. Implants can work in place of the hair cells, but if the sensory neurons are damaged, hearing is still limited.

"Obviously the ultimate aim is to replace both cell types," says Marcelo Rivolta of the University of Sheffield in the United Kingdom, who led the new work. "But we already have cochlear implants to replace hair cells, so we decided the first priority was to start by targeting the neurons."

In the past, scientists have tried to isolate so-called auditory stem cells from embryoid bodie—aggregates of stem cells that have begun to differentiate into different types. But such stem cells can only divide about 25 times, making it impossible to produce them in the quantity needed for a neuron transplant.

Rivolta and his colleagues knew that during embryonic development, a handful of proteins, including fibroblast growth factor (FGF) 3 and 10, are required for ears to form. So they exposed human embryonic stem cells to FGF3 and FGF10. Multiple types of cells formed, including precursor inner-ear hair cells, but they were also able to identify and isolate the cells beginning to differentiate into the desired spiral ganglion neurons. Then, they implanted the neuron precursor cells into the ears of gerbils with damaged ear neurons and followed the animals for 10 weeks. The function of the neurons was restored.

"We’ve only followed the animals for a very limited time," Rivolta says. "We want to follow them long-term now"—both to assess the possibility of increased cancer risk and to observe the long-term function of the new neurons, he adds.

"It’s very exciting," says neuroscientist Mark Maconochie of Sussex University in the United Kingdom, who was not involved in the new work. "In the past, there has been work where someone makes a single hair cell or something that looks like one neuron [from stem cells], and even that gets the field excited. This is a real step change."

The question now, he says, is whether the procedure can be fine-tuned to allow more efficient production of the relay neurons—currently, fewer than 20% of the stem cells treated develop into those ear neurons. By combining growth factors other than FGF3 and FGF10 with the stem cell mix, researchers could harvest even more ear progenitor cells, he hypothesizes.

"The next big challenge will be to do something as effective as this for the hair cells," Maconochie adds.