Information Processing and Proactive Interference in Children With and Without Specific Language Impairment
A recent study was conducted to see if children with a Specific Language Impairment (SLI) will differ from their peers in resistance to proactive interference under different conditions. Proactive interference is the difficulty of learning new information because of already existing information. Evidence has shown that children with SLI have a deficit in inhibition control, to focus on relevant information in presence of irrelevant information. People who are more efficient in resisting interference from irrelevant information (external or internal) have more free working memory capacity. This information is what began the research to examined whether problems in proactive interference contribute to the working memory deficit in children with SLI.
Only a few studies have looked at executive functions such as inhibition control, or sustained attention with children with a SLI. Those findings show that children with SLI show slower development than Typical Language Development (TLD) peers but disappears once they get to school age. When looked at all the different studies, it suggest that problems of children with SLI are not limited ot specific modalities. After these findings the study here was to focus on resistance to proactive interference. Two questions were to be answered from the study: Experiment 1: Do children across groups show same degrees of interference in a condition where previous target items become distractors? Experiment 2: Do children’s responses to items follow a highly practiced item show an increase in reaction item reflecting greater proactive interference?
Three groups were formed based on age and language status, 22 child with SLI, 22 children with typical language development and 22 language-matched controls. All the children spoke English as primary language and had normal hearing based on the hearing screen. Also no other developmental disorder besides SLI. All children scored within the average range on the Test of Nonverbal Intelligence-Third Edition. From previous findings children with SLI were expected to perform poorly from peers. The children were required to listen to a long lists of items (2-6 items) belonging to a particular category(ex.animals), then reorder and repeat the items based on a given criterion (ex increasing size). Several standardized language measures where administered to the children to determine which group was appropriate.
The first experiment included manipulations to increase proactive interference by using previous target words as distractors. If the items from previous trail aren’t deleted from working memory efficiently, then recalling relevant information becomes more difficult. Out of the 168 items, a distractor was presented on 48 items, half of these distractor items (24) were words from previous category. The other 24 distractors did not belong to any category previously, they served as a baseline condition. Performance on items that used previous target words as distractors in trials was used to measure resistance to proactive interference. The 3 groups did not differ in baseline performance, but vocabulary size did show a positive effect on performance accuracy. The findings were that the interference condition has a negative effect on all children’s performance. The negative effect is larger in children with Specific Language Impairment (SLI) than in Typical Language Development (TLD) children. In each condition the younger children were slower than the older participants.
Experiment 2 will view the interactions between working memory and interference. The repetition of the item in a category should increase that item’s representation in working memory and make it hard inhibit same response on the next trial because of interference. Children with SLI are expected to take longer to build strong working memory due to previous evidence. The same groups of children were used in this experiment. The children were presented with 6 target items (six different, 14 item blocks) four times, they were not informed that items were repeated and how to perform task in usual manner. The results were that SLI showed similar improvement in performance but more gradually, they required 2-3 repetitions to achieve the same increase in accuracy that TLD achieved in a single repetition. Overall the second study showed us that children with SLI need to work harder than their peers to achieve the same goals, which may overload their system.
The results show us that children with SLI have a weaker resistance than their peers to proactive interference. SLI children show difficulty with suppressing irrelevant information, make more interference errors than typically developing children and show a slower rate of implicit learning. If you notice your child having trouble in any of these areas of language please contact a certified or licensed Speech Language Pathologist for an Evaluation.
Journal of Speech, Language, and Hearing Research February 2014, Vol.57, 106-119. doi:10.1044/1092-4388(2013/12-0306)
History: Accepted 02 May 2013 , Received 21 Sep 2012 , Revised 20 Feb 2013