Retroactive interference arises when a new learning affects a previous recall. For instance, in an experimental procedure, a list of words, A, is presented. After that, a new list, B, is shown. Retroactive interference comes when the learning of the new list (B) affects the recall of the list first presented (A).
Forgetting: Time Passing or Interference?
This interference effect is related with the nature of forgetting (Baddeley et al. 2009). The first author interested in the dynamic of forgetfulness was Hermann Ebbinghaus. This scientist, crucial in the study of the roots of memory, drew the forgetting curve (Ebbinghaus 1885) to try to explain how memories vanish along time. Ebbinghaus proposed that to forget is due to the decline of the information by the passing of time.
After Ebbinghaus, theories based in association started to claim the concept of interference as the motor of forgetting (Ruiz-Vargas 2010). According to interference theory, the loss of information is not only due to the passing of time, but could also be caused by different situations and competing cues in the learning process and subsequent memories.
To unravel if forgetting is due to time passing or mediated by other experience interferences, the paradigm of dream and wakefulness was used by memory topic researches. In this procedure, the dream phases are used to induce time lapses without interferences or physiological changes due to learning in wakefulness.
Jenkins and Dallenbach (1924) were pioneers in the use of this paradigm. In their study, students from Cornell University had to learn series of 10 meaningless syllables. Series were repeated until they were totally learned by participants. When they were able to correctly repeat all the stimuli, the series were later recovered in a 1, 2, 4, and 8 h delay. This recall test could be in a dream condition or in a wakefulness condition. Results showed that forgetfulness was higher in wakefulness than in the dream condition. These data suggested that forgetting was not only caused by the passing of time, but was also influenced by experiences in the wakefulness phase.
Anyway, this procedure has problems because of different levels of processing occurring during sleep, and it is not equivalent to not having experiences on processing. On the other hand, another hypothesis considers that consolidation during dream phase could enhance the recall (Mercer 2015).
Variables that Modulate the Interference
Within the variables implicated in the modulation of interference theory, time interval between the first and the second list presentation can influence interference. Another relevant factor that modulates the strength of information overlap is the similarity of the information. The more similarity in stimuli to recall, the more interference. For example, McGeoch and McDonald (1931) asked their participants to learn a list of adjectives. One group learnt a list and took a rest after for 10 min. The other group learnt the list and another list of different adjectives immediately afterward. Both groups were tested and asked for the first list. They also manipulated the similarity of the list in the last group and found that the highest forgetting rate was observed when the second list presented synonymous of the first list. This study and others showed that the more similar the material to learn is, the most marked retroactive interference effects are found.
- Baddeley, A., Eysenck, M. W., & Anderson, M. C. (2009). Memory. New York: Psychology Press.Google Scholar
- Ebbinghaus, H. (1885). Über das gedächtnis Leipzig: Dunker (Trad. Nueva York: Dover, 1964).Google Scholar
- Ruiz-Vargas, J. M. (2010). Olvido. In J. M. Ruiz-Vargas (Ed.), Manual de Psicología de la Memoria (pp. 254–272). Madrid: Síntesis.Google Scholar