May 22 (HealthDay News) -- Infants as young as 5 months old can distinguish between similar-looking liquids and solids, an indication that babies are always learning and pretty smart to begin with, new research suggests.
Two Northwestern University experiments found that babies would stare longer at objects that did new or unexpected things and then would make decisions on what it was they'd observed -- a reaction that adults also have when introduced to something different.
"Our research on babies strongly suggests that right from the beginning, babies are active learners," lead author Susan Hespos, an assistant professor of psychology at Northwestern's Weinberg College of Arts and Sciences, said in a university news release. "It shows that we perceive the world in pretty much the same way from infancy throughout life, making fine adjustments along the way."
In the first experiment, two groups of 5-month-olds were shown either a glass of blue water or one with a solid blue object inside. The glass was tilted back and forth so the babies could see how the substance inside reacted to the motion. The babies then watched as the researcher poured both the liquid and the solid from one glass into another.
The babies all took more time to study the transferring of the object they didn't see in the tilting portion of the experiment, whether it was the liquid or the solid.
"As capricious as it may sound, how long a baby looks at something is a strong indicator of what they know," Hespos said. "They are looking longer, because they detect a change and want to know what is going on."
In the next experiment, the babies again were shown either a liquid or a solid in a glass being tipped back and forth. They then watched as researchers lowered a cylindrical pipe into both sets of glasses. As in the first round, the babies looked longer when the pipe was placed into the glass they hadn't seen in the tilting portion of the experiment.
The researchers said that's because the visual motion cues they had seen in the first part led the babies to expect something different than what happened when the pipe entered the other object in the glass.
"Together these experiments provide the earliest evidence that infants have expectations about the physical properties of liquids," the researchers concluded. Their findings appear in the May issue of Psychological Science.
They also reinforce the idea, the researchers said, that babies are not blank slates who depend on others to acquire knowledge.
"Our research shows that babies are amazing little experimenters with innate knowledge," Hespos said. "They're collecting data all the time."
SOURCE: Northwestern University, news release, May 2009