Monday, April 8, 2013

Development of Declarative Memory in Infants

This week, I read a study regarding the development of declarative memory in infants. The study was held at the University of Otago in 2000. The researchers utilized two experiments to follow changes in declarative memory, or explicit memory in infants over the course of the first 2 years of life. The researchers were interested in discovering information about the emergence of multiple memory systems in infancy. It is understood that memory functions as two or more systems; but when these systems emerge is under question. 

The first experiment method required infants 12 and 18 months old. The infants participated in a demonstration session and a test session; some were used as the control subject. The infant interacted with the experimenter until they were comfortably playing. Then, the experimenter introduced a puppet to the infant. While the infant watched, a mitten was removed from the puppets hand with a bell inside, the researcher shook the mitten three times sounding the bell. The control infants were subjected to the same puppet but it was out of the infant’s reach and the bell was attached to the puppets back. The infants were then brought back to the lab 24 hours later for a test session. The researchers videotaped the infants as they interacted with the puppet. They observed if the infants performed the target behaviors they demonstrated 24 hours prior to the test session (remove the mitten, shake the mitten, and put the mitten back on the puppet). The experiment found that there were age related differences in regards to the retention of the target behaviors. 12-month-olds tested with the same puppets performed the target behavior less accurately than the 18-month-olds. 12-month-olds also did not perform the target behaviors with different puppets. The 18-month-olds performed the target behaviors with the original test puppet as well as an additional test puppet that they had not been introduced to previously. The first experiment lead the researchers to investigate at what age an infant is able to “generalize across context”; or to perform the target behaviors with both the original test puppet and a newly introduced puppet. 

Experiment two tested the “effects of altered cues on deferred imitation by 6-month olds”. They established that 6-month olds did not imitate the target behaviors after a 24-hour period when shown the action three times for 20-30 seconds. The experiment, instead, tested the 6-month olds six times for 20-30 seconds to see if the target actions were achieved when tested 24 hours later. The procedures for the second experiment was just as experiment one, but the action was repeated six times. The data produced from this experiment showed that fewer 6-month-olds positively performed the  target behaviors than the 12-month-old pool of participants. Additionally, even fewer participants in the group of 6-month-olds were able to perform the target behaviors with a different puppet. 
The results from the experiments demonstrate that deferred imitation in infants occurs between 6 and 12 months of age. This development of declarative memory allows the infants to use memories of past experiences and apply them to new situations. The lab showed that while 6-month olds are able to repeat the task on the same puppet, 18-month-olds are able to apply the learned behaviors to new puppets. 

This lab concludes by discussing the decline of childhood amnesia. The researchers suggest that the lost memories between birth and three years old can be attributed to “age-related changes in the encoding, organization, retrieval and expression of memory”. The lab revealed the significance of the conditions of the first demonstration of the target actions. There is a close link to the environmental conditions of the original encoding of the behavior and the ability to perform that same behavior later.
To me, the most interesting aspect of this study was the development of the infants ability to repeat the target actions on a puppet they were not originally shown. This is an indication that the infant is beginning to develop memories that they store and utilize in appropriate situations. I am curious as to how the infants ability to recall different behaviors would be in an urgent situation. Could an infant be taught to perform lifesaving behaviors as young as 6-months old? I wonder if the infant was taught to float while in a pool as in infant; would that infant remember to float should they fall into the pool? 

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