Part 1:Transfer Of Working Memory Training To The Inhibitory Control Of Auditory Distraction
Mar 20, 2022
Contact: joanna.jia@wecistanche.com / WhatsApp: 008618081934791
Received: 26 August 2020 / Accepted: 18 December 2020 / Published online: 15 January 2021
© The Author(s) 2021
Abstract
Extended working memory training with the dual n-back task has been shown to improve performance on various untrained cognitive tasks, but previous findings were inconsistent with regard to the extent of such transfer. The dual n-back training task addresses multiple components of working memory as sequential information from two different stimulus modalities needs to be simultaneously encoded, maintained, continuously monitored, and updated in working memory while irrelevant information needs to be inhibited. However, it is unclear which executive functions account for the observed transfer effects. In this study, the degree of inhibitory control required during training was manipulated by comparing two versions of the dual n-back task in which participants are asked to either respond or withhold a response on the less frequent trials when an item was identical to an item n trial back. Eight 80-min sessions of training with adaptive versions of both n-back tasks were shown to improve working memory updating. Moreover, in contrast to the standard n-back task, training on the inhibitory n-back task was found to reduce the interference in working memory produced by task-irrelevant speech. This result suggests that enhanced demand for inhibitory control during training enables transfer to the inhibition of distractor interference, whereas the standard n-back task primarily affects working memory updating. The training effects did not transfer to the inhibition of spatially incompatible responses in a Simon task, and it yielded no far transfer effects to untrained executive functions or measures of fluid intelligence.
Keywords Working memory training · n-back task · Inhibitory control · Distractor interference · Irrelevant speech effect
Transfer of working memory training to the inhibitory control of auditory distraction
Working memory refers to a cognitive system of limited capacity that enables temporal storage and processing (e.g., manipulation, monitoring) of information to support thought and action processes (see Baddeley 2003; Cowan 2017; Miyake and Shah 1999). It has been shown that individual differences in the capacity of working memory are related to several complex cognitive or verbal abilities, such as reasoning (Fry and Hale 1996; Kyllonen and Christal 1990), problem-solving, and general intelligence (e.g., Conway et al. 2003; but see Harrison et al. 2013), reading comprehension (Daneman and Carpenter 1980;
Engle et al. 1991), and selective listening in cocktail-party situations (Conway et al. 2001). Working memory impairment, on the other hand, has been associated with attention deficits and learning disabilities (Alloway 2009; Marti- Hussein et al. 2005). More recently, several studies demonstrated that working memory capacity can be enhanced through extensive cognitive training, both in children and adults, leading to improvement on various cognitive tasks addressing reading comprehension, executive control, episodic memory, or fluid intelligence (Buschkuehl et al. 2008; Chein and Morrison 2010; Dahlin et al. 2008a, b; Jaeggi et al. 2008, 2010; Klingberg et al. 2002; Salminen et al. 2012; Schmiedek et al. 2010; Thorell et al. 2009). Several well-controlled studies, however, failed to replicate these widespread transfer effects resulting from working memory training (Melby-Lervåg and Hulme 2013; Redick et al. 2013; Thompson et al. 2013). Therefore, reviews and meta-analyses on the efficacy of working memory training drew rather inconsistent conclusions (Au et al. 2015; Dougherty et al. 2016; Karbach and Verhaeghen, 2014; Melby-Lervåg et al.2016; Melby-Lervåg and Hulme 2013; Soveri et al. 2017; von Bastian and Oberauer 2013b). There is still an ongoing debate regarding the specific cognitive functions that ben- eft from working memory training, and to what extent the training-related improvement of these functions yields transfer to untrained tasks that require more generalized cognitive abilities, such as cognitive flexibility, problem-solving, or fluid intelligence. From the empirical data available, it can be concluded that transfer of working memory training is more likely in transfer tasks that are structurally similar to the trained tasks (near transfer) than when the transfer tasks share only a few features with the trained task (far transfer), but there is still very little understanding of the exact cognitive mechanisms and components of working memory that enable transfer (Gathercole et al. 2019; Shipstead et al. 2010; Simons et al. 2016).
Most models of working memory distinguish (a) one or multiple storage buffers or maintenance components from (b) a component for executive control which enables monitoring and manipulation of the stored information (Baddeley 1996, 2003; Baddeley and Hitch 1974; Engle 2002; Miyake and Shah 1999; Oberauer et al. 2000). Cognitive training tasks, such as the dual n-back task, which has been shown to successfully enhance working memory capacity (i.e., the number n of items to-be-updated in working memory; see Jaeggi et al. 2008), typically require both maintenance and executive control (e.g., updating) of the information in working memory, but it is still unclear which executive functions benefit most from cognitive training, and how the training-related improvement is related to transfer. Working memory updating and monitoring, set-shifting (i.e., cognitive flexibility or task-switching), and inhibition was found to be the three major functions of executive control, which are involved in many cognitively demanding tasks (Miyake et al. 2000), but a majority of studies on working memory training seem to have used tasks that primarily require the updating and monitoring component (e.g., Dahlin et al. 2008a, b; Jaeggi et al. 2008; Kühn et al. 2013; Lilienthal et al. 2013; Salminen et al. 2016). In a typical dual n-back task, participants are presented with two running sequences of stimuli (auditory and visual) from which the items of the last few (n) trials only need to be memorized. The participant's task is to indicate whether any of the two items on the current trial is identical to one of the items that were presented exactly n trials before. Hence, it is required to continuously monitor and update the information to be maintained in working memory, but the task may also involve inhibition of currently irrelevant items and attention shifting between the two sequences of stimulus modalities. More specifically, it has been suggested that the n-back task requires not only encoding, storage, and rehearsal of items, but also discarding (inhibition) of previously encoded items and repositioning (updating) of the to-be-remembered information in working memory (Postle et al. 2001). While the empirical results are still scarce and also inconsistent, there is some evidence suggesting that extended training on the dual n-back task does indeed improve updating and monitoring, whereas it may not necessarily generalize to other functions of executive control, such as set-shifting or inhibition (Dahlin et al. 2008a, b; Salminen et al. 2012; von Bastian and Oberauer 2013a).
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The purpose of the present study is to investigate whether working memory training can be used to enhance the inhibitory control function of working memory. Individual differences in the strength of inhibitory control were shown to predict both the development and the age-related decline of cognitive abilities (Diamond and Gilbert 1989; Hasher and Zacks 1988; Salthouse and Meinz 1995). These findings suggest that inhibitory control may benefit also from cognitive training, which might have important implications in particular for maintenance of inhibition in the older age. However, it has been argued that inhibition may not be a unitary mechanism, but to refer to three functionally distinct processes (see Friedman and Miyake 2004): (1) suppression of pre-potent or automatic responses (as in a Stroop task; Stroop 1935), (2) inhibitory control of the interference produced by irrelevant stimuli (as in a flanker task; Eriksen and Eriksen 1974; or in an “irrelevant sound paradigm”; Jones and Macken 1993; Salamé and Baddeley 1982), and (3) inhibition of information in memory (e.g., to avoid proactive interference). It has been found that inhibition of pre-potent responses and inhibition of irrelevant stimuli (interference control) may be closely related, whereas inhibition of proactive interference seems to be a separate process (Friedman and Miyake 2004).
While there is some indication that pre-potent response inhibition can be improved with practice (in particular when combined with transcranial direct current stimulation; Ditye et al. 2012), very little is known about the possible efects of an extended working memory training on the other forms of inhibitory control. Here, the efect of two diferent types of working memory training, varying in the degree of inhibitory control required, were compared with regard to their transfer efects on (a) the ability to suppress pre-potent responses (response inhibition) and (b) the ability to inhibit interference from irrelevant auditory information (resistance to auditory distraction). Specifically, one group of participants was trained on a standard dual n-back task which is supposed to involve primarily updating and monitoring of contents in working memory (Braver et al. 1997; Jaeggi et al. 2007), and possibly to some extent other inhibitory control processes, such as the inhibition of irrelevant stimulus information (Postle et al. 2001). To experimentally enhance the degree of inhibitory control involved in the dual n-back, a second group was trained on an “inhibitory” version of the dual n-back task (inhibitory n-back) in which responses had to be given predominantly, and participants had to occasionally inhibit the response depending on the current information held in working memory (i.e., on “n-back trials”). Both types of n-back training are expected to enhance working memory updating skills which were tested with an untrained visual updating task before and after training (adopted from Dahlin et al. 2008a). Moreover, assuming that response inhibition and resistance to distractor interference are closely related (Friedman and Miyake 2004), any training-related improvement on the inhibitory dual n-back task may be expected to induce more transfer to performance in other tasks that require either the suppression of pre-potent responses or inhibitory control of irrelevant stimuli, compared to the standard dual n-back task with lower demands for inhibition. Therefore, the transfer of the two types of working memory training was assessed in terms of both response inhibition and the degree of interference produced by auditory distractors. In addition, far transfer was tested for unrelated executive functions (i.e., task-switching) and more generalized cognitive abilities (i.e., problem-solving skills related to fluid intelligence) for which transfer was reported previously (e.g., Jaeggi et al. 2008).
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Generalization to response inhibition was assessed with the Simon task (Hedge and Marsh 1975) in which a target is presented at a location that is either spatially compatible or incompatible with the location of the response. Specifically, on compatible trials, a response needs to be made by the hand that corresponds to the location of the target (the pre-potent response), whereas on incompatible trials, the response needs to be made by the other hand and the pre-potent response needs to be inhibited. Typically, response time increments are observed on incompatible trials, as compared to compatible trials (the Simon efect). The inhibitory working memory training could be expected to afect response inhibition: If the training-related enhancement of inhibitory control enhanced the ability to suppress pre-potent, dominant, or automatic responses (Friedman and Miyake 2004), then reduced Simon efects should be observed at post-test in the inhibitory n-back group.
In addition, transfer of the inhibitory training could be expected also with regard to inhibitory control of auditory distraction. It is well known that task-irrelevant sounds, such as speech or random tone sequences, disrupt performance in serial short-term memory tasks (e.g., Colle and Welsh 1976; Jones et al. 2004; Jones and Macken 1993; LeCompte et al. 1997; Salamé and Baddeley 1982). While these disruptions were originally explained with speech-related interference-by-content in the “phonological loop” (Baddeley and Hitch 1974; Salamé and Baddeley 1982), it has been shown later that similar disruption can be produced also by non- phonological sound (e.g., changing tones; Jones and Macken 1993), and it has been suggested that the interference may be specifc to the processing of serial order in short-term memory (e.g., Jones and Macken 1993, 1995). More specifically, according to the object-oriented episodic record account (Jones et al. 1996), auditory distraction is assumed to be a by-product of perceptual organization processes which enable the segregation and grouping of auditory objects (during auditory scene analysis; Bregman 1990). Any change in the state of background sound is expected to give rise to the formation of a new auditory object, which is automatically linked to the previous objects (using “pointers”), thus creating an ordered stream. In a serial recall task, articulatory rehearsal can be used (as a motor planning process) to deliberately form and refresh links between to-be-remembered items, thus enabling the maintenance and retrieval of serial information. However, automatic processes of auditory perceptual organization form additional links between task-irrelevant changing-state sounds, which then interfere with the deliberate motor planning and rehearsal processes during serial recall. In line with this interference-by-process account (Hughes and Marsh 2017; Jones et al. 2004; Jones and Macken 2018), it has been found that the degree of dis- traction increases with the magnitude (e.g., the distance in pitch between successive tones; Jones et al. 1999) and the number of changes between successive task-irrelevant auditory events within a given time interval (i.e., the word/token dose efect; Bridges and Jones 1996; Tremblay and Jones 1998, Exp. 5). In addition, changing-state sound (speech or varying tones) was found to disrupt performance in a serial recall task, but not in tasks that do not require serial-order processing (e.g., the “missing-item task”; Beaman and Jones 1997; Hughes et al. 2007; Jones and Macken 1993), unless participants happen to adopt a serial rehearsal strategy (Beaman and Jones 1998; Hughes and Marsh 2020b). In addition to this task-specific interference with serial-order processing, it has been proposed more recently that auditory distraction may arise also from attentional capture, with meaningful or acoustically deviating sounds diverting attention from the focal task (see the “duplex-mechanism account”; Hughes 2014; Hughes et al. 2005). In contrast to interference-by-process, this form of distraction appears to be less specifc to serial-order processing (affecting performance also in non-serial short-term memory tasks; e.g., the “missing-item task”, Hughes et al. 2007; Vachon et al. 2017), and it may be more susceptible to cognitive control than interference-by-process (Hughes et al. 2013; Hughes and Marsh 2020a). Moreover, it has been reported that the degree of attentional capture elicited by auditory deviants, but not the changing-state efect (indicating interference- by-process), was related to the participant's working memory capacity (Hughes et al. 2013; Sörqvist et al. 2010)(but see Körner et al. 2017). It is not entirely clear to what extent the disruptive efect of irrelevant speech on serial recall is caused by acoustical interference with serial-order processing and attentional capture, but there is evidence suggest- ing that at least meaningful speech (e.g., full sentences as compared to lists of changing-state syllables or words) may disrupt performance through both mechanisms (see Bell et al. 2017; Hughes and Marsh 2020b). Moreover, the findings of reduced disruption of serial recall (1) after repeated presentation of the same stream of irrelevant speech (i.e., habituation; Banbury and Berry 1997; Bell et al. 2012), (2) in blind listeners with enhanced auditory processing abilities (Kattner and Ellermeier 2014), and (3) following a specific training of auditory attention (Kattner and Ellermeier 2020) suggest that disruptive effect of irrelevant speech can be partially attributed to the diversion of attention.
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In the present study, the transfer of cognitive training was assessed in terms of the disruptive effect of task-irrelevant speech, compared to noise, on serial recall. If the disruptive effect of speech depended on general working memory capacity, then it would be expected that both cognitive pieces of training with the dual n-back task will reduce distraction. In contrast, if auditory distraction was specifically related to inhibitory control of irrelevant sound, then the inhibitory n-back training should result in greater attenuation of auditory distraction than the standard n-back training with fewer demands for inhibitory control. Specifically, the inhibitory n-back training might enhance the ability to resist or resolve interference from the external environment (Friedman and Miyake 2004). In line with the duplex-mechanism account of auditory distraction, it could be argued that attentional capture by irrelevant speech is likely to depend on inhibitory control, whereas the disruption due to changing-state sound (in irrelevant speech) should not depend on any form of cognitive control (Hughes 2014; Hughes et al. 2013). Therefore, enhanced inhibitory control (or resistance to interference from the external environment) could be expected to prevent the diversion of attention by irrelevant speech, whereas the presumably uncontrollable disruption due to the changing-state nature of speech should remain. A training of inhibitory control should thus lead to attenuation, but not to full elimination of the irrelevant speech effect. Alternatively, it could be argued also that enhanced inhibitory control of irrelevant changing-state sound (e.g., inhibiting the formation of irrelevant auditory streams) may reduce the specific interference between auditory grouping and the seriation process, which might then lead to a stronger attenuation or even an elimination of the irrelevant speech effect.
In addition to the transfer effects on performance in tasks that involve similar executive functions as the training tasks—working memory updating, suppression of pre- potent responses (Simon effect), and resistance to interference by irrelevant speech—the present study also tested the possibility of far transfer effects on (a) the response-time costs resulting from task-switching (indicating cognitive set-shifting abilities; Rogers and Monsell 1995) and (b) general problem-solving capabilities, which are related to fluid intelligence (Jaeggi et al. 2008).
