Development of the Understanding of Symbols


A typical 19 month old can point out objects in pictures...but cannot yet produce them.

What change in reaction to pictures takes place between the ages of 9 and 19 months?

Around the age of nine months, babies do not understand that items seen in pictures cannot be handled. DeLoache, Pierroutsakos, Uttal, Rosengren, and Gottlieb (1998) studied 9-month-olds in two very different cultures, the United States and the Ivory Coast, and found the same behavior in each: babies treated objects in pictures as if they were real objects, "even trying to pick them up off the page." By the time they were 19 months old, they stopped that behavior and simply pointed at objects in pictures.

Children are somewhat slower to understand symbols that relate to real-world objects. A symbol bears an abstract relationship to a real-world object or event. For example, maps are symbolic representations of environments. A 3-year-old typically cannot understand the purpose of a map.

How did DeLoache investigate symbolic abilities of 3 year olds?

In one ingenious experiment, DeLoache (1995) studied the ability of small children to form symbolic relationships. The experimental task involved toys that were hidden in a big room or a smaller model of the same room. The experimenter showed where the toy was hidden in one room, and the child was supposed to find the corresponding toy in the other room. For example, a teddy bear might be hidden behind a couch pillow in the big room, then the child was supposed to find a very tiny teddy bear hidden behind a miniature pillow on the little couch in the model.

Why did the 30-month-olds fail?


The incredible shrinking machine at work

Three-year-old children (36-month olds) typically "got" this. They could find the little teddy bear in the model, if they saw the big one being hidden in the larger room. However, 30-month-olds, just six months younger, usually did not get it. They saw the toy being hidden in the big room, but when given access to a model that was identical to the big room, they explored randomly. DeLoache hypothesized that 30-month-olds were not yet able to form abstractions. They saw the resemblance between the two rooms, but they did not treat the little room as a map of the bigger room, or vice versa.

Next DeLoache tricked a group of 30-month-olds. She told them she had a shrinking machine that could shrink the big room down to a small one. To demonstrate the shrinking machine, she showed the children a large troll doll. It was placed near the shrinking machine, then the experimenter and the child went into another room where they listened to computer generated "sounds the shrinking machine makes when it's working." They came back into the experimental room to find a tiny troll by the shrinking machine. The children were completely fooled. They believed the troll had shrunk. ("Remember, most of these children also believe in the tooth fairy," DeLoache pointed out.)

What happened when 30-month-olds thought the room had shrunk?

Now came the pivotal part of the experiment. DeLoache showed children the large room, then they left the area while the shrinking machine operated. When they returned, the big room (a tent-like structure) was gone, and the little model room was there instead. "The sight of the model in place of the room was very dramatic," reported DeLoache.

Now that the 30-month-olds had thought it was the same room only smaller, they had no trouble finding a toy in the model at the same place where it had been left in the big room. This clever demonstration showed that their problem, in the earlier task, was forming a symbolic representation to relate the two spaces. When that problem was eliminated, they had no trouble with the task. Nothing had really changed except the way the children interpreted the situation—they thought they were dealing with one space, instead of two—but that was enough to overcome the difficulty they had earlier. It also pinpointed what they were lacking at 30 months: the ability to form an abstract relationship between two spaces.

How does this research continue the theme established by Piaget?

Although DeLoache never mentioned Piaget, this research continued the theme established by Piaget over 50 years earlier. Children are not born with all the mental structures they need to interpret events in the world. They cannot necessarily represent abstractions like liquid quantity or map of a room. They gain such representational abilities as they develop, and clever experiments can show when each cognitive skill appears.

Can mature chimpanzees perform this task?

Mature chimpanzees evidently do have the ability to form an abstract relationship between two species, as operationally defined by this task. Their behavior is like that of older humans. Sarah Boysen, whose ingenious work with chimps was mentioned in Chapter 8, demonstrated this on the television program Scientific American Frontiers. Dr. Boysen hid a miniature soda can in a dollhouse, and the chimpanzee immediately retrieved it from the corresponding place in the larger room. Unlike 30-month-old humans, adult chimpanzees had the ability to use one space to map another.


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Copyright © 2007 Russ Dewey