As the foregoing sections show, the effect of task-irrelevant background on short-term memory has been widely assessed and this research has identified specific forms of disruption to recall. In the interest of clarity, this section summarises the definitions of the most commonly used terms, acronyms, and tasks used in the irrelevant sound paradigm and in the thesis.
1.5.1 Irrelevant speech effect or irrelevant sound effect (ISE).
This refers to the finding that recall performance in the presence of irrelevant speech or sounds is lower than in quiet (e.g., Colle & Welsh, 1976; Jones & Macken, 1993). The ISE has been observed with speech and non-speech sounds and hence the term Irrelevant Sound Effect is used to encompass distraction from both these sources. Within the thesis, the ISE was assessed as the difference between recall performance in quiet and individual irrelevant speech conditions, regardless of whether the speech was steady- or changing-state, or contained deviants (see below).
1.5.2 Changing-state effect.
A changing-state auditory sequence is one wherein each element in the sequence is different to the preceding one (e.g., A – B – A - B) while in a steady-state sequence a single item is repeated (e.g., A – A – A – A). The finding that recall performance is
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lower in the presence of changing-state speech or sounds compared to steady-state is known as the CS effect (e.g., Hughes et al., 2007; Macken et al., 1999). This pattern of disruption has been observed in the literature consistently but only when the memory task required items to be recalled in the order they were presented (Beaman & Jones, 1997; Hughes et al., 2007). This process of remembering items in order is often supported by a serial rehearsal strategy whereby items are repeated subvocally in the order they were presented. As such, the CS effect is thought to occur only in those tasks that invoke serial rehearsal (e.g., Beaman & Jones, 1997). The CS effect in the present experiments was calculated as the difference between recall scores in changing-state, versus steady-state, speech.
1.5.3 Deviation effect.
This refers to the capture of attention by unexpected changes in the irrelevant auditory stream (Hughes et al., 2007; Vachon et al., 2012). When there are elements in the auditory stimulation that deviate from the prevailing pattern (e.g., G – G – G – G – L) the unexpected element triggers attention capture away from the focal task and towards the deviant in the auditory sequence (Hughes et al., 2007). In comparison to the CS effect, the deviation effect is not sensitive to the processes engaged by the focal task and is manifest in a wide range of tasks such as categorization tasks (Parmentier, 2008), visual and audio-visual search tasks (Dalton & Lavie, 2004; Dalton & Spence, 2007), and the missing-item task (Vachon, Labonté, & Marsh, 2016). In the current series, the deviation effect was the difference between performance in steady- or changing-state speech with and without deviants.
1.5.4 Short-term memory tasks used in the thesis.
Serial recall, probed recall, and the missing-item task are commonly used short- term memory tasks within the irrelevant sound paradigm. TBR items in these tasks are
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often digits (e.g., Hughes & Jones, 2005) and letters (Jones et al., 2004) but can also comprise words (e.g., Marsh, Hughes, Sörqvist, & Beaman, 2015) and pictures (e.g., Klatte et al., 2010). While these tasks differ in terms of the involvement of rehearsal, their successful performance requires the focus of attention. The serial recall and probed recall tasks are thought to require the use of serial rehearsal while the missing-item task does not. The contrast between tasks on the basis of rehearsal involvement is an
opportunity to show how the motor-articulatory processes that support rehearsal are affected by auditory distraction and to identify how the developmental differences in motor-planning processes can dictate the level of distraction that is observed.
Serial recall.
In this task, the objective is to reproduce a list of items in the order of presentation. A common strategy used to complete this task is serial rehearsal – repeating the items subvocally in the order that they were presented.
Probed recall.
The retention of order information is also crucial in this task but the response demands vary compared to a typical serial recall task. Instead of recalling the entire list of items in order, the task requires identification of the item that followed another in the list. For example, the list presented could be ‘5 4 7 2 1’ and at the recall stage
participants may be asked ‘Which digit followed ‘7’ in the list?’. Therefore, the order in which the items were presented must be retained to identify which item followed the probe. This task, like serial recall, calls upon motor planning which subserves serial rehearsal and the retention of order information.
Missing-item task.
The objective in this task is to identify the one item that was missing or omitted from the list. The TBR lists used for this task generally comprise a well-known or
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overlearned set of items such as digits from zero to nine (Beaman & Jones, 1997; Elliott et al., 2016; Hughes et al., 2007) or spatial locations of dots (Vachon et al., 2016). TBR items are presented in a similar fashion to the serial and probed recall tasks but at the recall stage, participants are asked ‘Which item was missing from the list?’. The crucial difference between the missing-item task and the other two tasks is the extent to which serial rehearsal is used. Unlike serial and probed recall tasks, the missing-item task is not thought to involve serial rehearsal because the retention of order of information is not essential to complete the task. In other words, the missing-item task does not require motor-planning. This task does, however, require attention for items to be encoded upon presentation and for the missing-item to be identified at recall.