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= Selective interference method (Cognitive Psychology) = Selective interference is a method paradigm mostly utilised within the field of Cognitive Psychology whereby secondary tasks are used to either impair or block processing in a given functional centre of the brain. The term was originally coined by Alan Baddeley as a way to describe his research methods which, along with Graham Hitch, allowed for the proposal of Baddeley's Working Memory Model, a model used to further examine the processes involved in short term memory. The idea being that a secondary selective interference activity can be introduced during a task that will induce interference or blocking of a given process.

History:
Selective interference methods may not have necessarily been first used by Baddeley, as interference methods in cognitive psychological research were common during the 1960s in research attempting to understand the separation of processing between short-term memory and long-term memory by interfering with rehearsal processes. Baddeley himself used these techniques before he coined the term, during his research (along with Denise Scott) into testing the Unit Sequence Interference Hypothesis, proposed by Underwood and Postman, testing if long-term memory could also be impaired via rehearsal interference just like short term memory.

As this method saw a sharp rise in popularity during the 1970s, most research that utilised it were based in behavioural research, where reaction times and accuracy scores were recorded and interpreted. Although, some more recent research has adapted this paradigm to suit neuroimaging research, in an attempt to localise where these processes take place; such recent studies have leant more evidence to previous research.

Procedure:
Baddeley used this testing method primarily in his research into the underlying processes involved in short-term memory, which later aided in his formation of the Working Memory Model. One significant strength of this method paradigm it is very flexible in that it can be used to examine a range of memory processes, from a broad process such as rehearsal to how a sub process such as spatial short-term memory handles different types of location information (see examples section for further research using this method). The underlying assumption of this method is that by introducing a secondary task or activity during a memory retention phase, it is possible to either block or interfere with the functional processes involved in the primary task. This is different than other interference paradigms as interference is induced in a selective and specific way, this interference can either be similar to the primary task or entirely different, depending on the researchers needs.

However, when using this method it is imperative that the selective interference method is indeed accurately selective and only interferes with the process that is selected for. This can become challenging in instances where a smaller sub-process is interfered, for example due to the similarity in how spatial and visual information are processed, it can be difficult to interfere with one process without interfering the other. This method paradigm may also be difficult to utilise when attempting to measure a sub process from a very broad overall process which shows significant overlap in how sub-processes interact, for example when attempting to interfere with the sub-processes in the executive system ; as it is difficult to interfere with one sub-process whilst leaving the others intact.

Examples:
Timothy Salthouse used this method in order to investigate whether nonverbal visual stimuli would be represented spatially in memory or in a more verbal format. Participants were asked to remember either the identity or position of seven items within a twenty five item array. The selective interference used in both tasks was a recognition memory task whereby they were shown photographs of faces and planes and asked verbally or nonverbally to select when images were the same or different (this changed each trial). Using this method Salthouse found that participants performed significantly worse in the trials using spatial stimuli when selective interference was used, whilst when identifying stimuli under interference along with verbal information the participants' performance was not significantly effected. Following the assumptions of selective interference, this shows that spatial and verbal information is processed in different systems, due to the lack of effect that selective interference had upon participants' performance.

Meudell also applied this method paradigm into their investigation in how verbal information (letters) and nonverbal information (location of squares) was processed and if there was any similarity. Two interference tasks were used, either counting backwards, or an eye tracking task; if participants in both primary tasks reacted to both interference methods in similar ways we could assume that these stimuli are processed in a similar way in memory. Results found that the verbal task was significantly effected by the counting-backwards interference method, whilst the nonverbal task was not effected by either of the interference methods. From this we can draw the conclusion that both verbal and nonverbal information are processed in significantly different ways with regards to working memory.

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