The article addresses the problems of interference as related to implicit memory. The study reveals the inconsistencies of the previous studies in the area of explicit and implicit memory, and the impact of interference on the memory performance. The authors of the article analyze the three major studies conducted in previous years. Lustig & Hasher (2001) refer to interference as “a primary source of forgetting and a major focus of memory research”.
Previous research has proved that implicit memory is immune to interference, but there is no evidence whether earlier studies have referred to proactive or retroactive interference. The results of the previous research have determined the different patterns of interaction between explicit memory, implicit memory, and interference mechanisms. This difference was later used to suggest that explicit and implicit memory tasks measure different forms of memory and act within different systems of the brain.
Despite the clear evidence that implicit memory is immune to interference, Lustig & Hasher (2001) suggest that this evidence is impaired by using wrong methods of research: the authors emphasize the importance of differentiating between target and nontarget memory responses. Lustig & Hasher (2001) have designed a new study, “in which each fragment presented at test could be completed only by one previously presented target word”. The authors have utilized the three-group study design: in the interference group, the nontarget items were similar to the correct completions; for the control group, nontarget items were unrelated to the test fragments; the third group was used as a baseline and received only test fragments. The control and interference group participants viewed a list of words divided into the two groups of target and nontarget items. The list was followed by a set of exercises to be completed by both groups (word-fragment test).
Lustig & Hasher (2001) used planned comparisons to analyze the results of the fragment-completion test. “The critical question was whether orthographically similar nontargets impaired implicit memory for the target words” (Lustig & Hasher, 2001). Although the control and interference groups have displayed better achievements in fragment-test as compared to the baseline group, the successes of the interference group members were negatively impacted by their exposure to the list of nontarget words. Thus, implicit memory was impacted by interference mechanisms. The authors have analyzed the proportion of incorrect answers as impacted by the group exposure to nontarget words.
The results have shown an increasingly great number of intrusions of the non-target words in the interference group as compared to the control and baseline groups. The results of the study, combined with the previous research results, have led to the conclusion that explicit memory cannot be the only critical factor in determining the presence of interference. On the contrary, the combination of the explicit and implicit memory responses determine the exact patterns of interference and their impact on human memory. Lustig and Hasher (2001) clearly demonstrate that implicit memory is not immune to interference. In addition, the researchers create a new vision of the critical boundary condition for interference, which “is similarity between critical and nontarget items, not deliberate retrieval” (Lustig & Hasher, 2001).
1. How is the interference phenomenon discussed in earlier studies?
2. Is there any unilateral evidence that implicit memory is immune to interference?
3. Why is the similarity between target and nontarget items potentially important for the investigation of interference and its impact on implicit memory mechanisms?
4. How has the use of fragment-completion test been beneficial for the discovery of interference impact on implicit memory?
5. In the light of the current research results, how can we define a critical boundary condition for interference?