Infants who used a plastic cane to get an out-of-reach toy were better able to understand the goal of another person's use of a similar tool than were infants who had previously only watched an adult use a cane to retrieve a toy.
"Only recently have there been studies showing that active, hands-on experience is a more effective way of learning than watching. This study indicates that there is a benefit to actual hands-on experience early in human development," said Jessica Sommerville, University of Washington (UW) assistant professor of psychology and co-author of the study.
In earlier work, Sommerville, who is affiliated with the UW's Institute of Learning and Brain Sciences, has shown that 10-month-old infants rarely use a tool such as a cane spontaneously.
To see if active, hands-on training provided greater understanding of another person's goals when using a tool, the UW researchers divided 51 infants - 26 boys and 25 girls - into three groups for the new study.
Those in one group, the training group, had an opportunity to use a red-striped and a green-striped cane to pull a rubber toy (such as a yellow duck and a purple hippopotamus) toward them on a table.
Then the infants were trained in how to use the crook of a cane to retrieve a toy. Finally, they were given two trials to see if they could pull the toy to them all by themselves.
A second group of infants, the observational group, went through the same procedure with one major difference. Instead of using the tools, the infants watched an adult mimic the babies in the first group learning how to use the cane to get a toy.
Finally the infants in those two groups, as well as those in the third, or baseline, group individually watched training trials in which a researcher seated behind a table used one cane to retrieve a toy and then picked up the toy, according to a UW release.
Then, out of sight of the babies, the location of the toy was switched in four test trials. In two of the trials, the crook of the same cane she had previously used was placed around a new toy. In the other two trials, the crook of a new cane was placed around the same toy as in the training trials. All of the babies were filmed during the test trials to see how long they watched each trial.
Sommerville said the experiment was designed to see if the infants would pay attention to a change in the experimenter's goal of getting a new toy rather than using a different tool. Infants in the observational and baseline groups spent equal amounts of time looking at the new cane and toys trials. But the trained group spent more time looking at the new toy trials, suggesting they understood that the adult was using the cane as a tool.
Even more striking was the fact that infants in the training group who were the most proficient at retrieving a toy - looking at the toy, purposefully pulling the cane to bring the toy to them and then quickly grasping the toy - were more likely to look at the new toy trials for a longer time.
These results were published in the current issue of the journal Developmental Psychology.