Fine particles, which are about 1/30th the average width of a human hair, come from a variety of sources, including vehicles, smokestacks and fires. They also form when gases emitted by power plants, industry and vehicle engines react in the atmosphere. The particles can aggravate heart and lung diseases.
Toddlers just learning to speak associate words with shape, not size or texture. Anything shaped like a telephone, for instance, might be called "phone." But a new study suggests that dogs tend to associate words with size rather than shape. This difference makes it "very doubtful that there is a single mammalian feature in word learning," said Emile van der Zee, a psychologist at the University of Lincoln in England and the first author of the study in PLoS One. The researchers worked with Gable, a 5-year-old border collie with an understanding of more than 40 words. Gable was shown a horseshoe-shaped object and over time the dog began to identify other objects of similar size and texture the same name.
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