Developmental differences in the irrelevant speech effect

Klatte, Lachmann, Schlittmeier et al. (2010) have suggested that while the magnitude of the overall irrelevant speech effect may not show a developmental

increase, attentional capture (i.e., the deviation effect) would reduce with increasing age as attentional control improves. However, many researchers have consistently found that children experience larger irrelevant speech effects than adults (e.g., Elliott, 2002; Elliott et al., 2007; Elliott & Cowan, 2005; Elliott et al., 2016; Meinhardt-Injac et al., 2015). The most recent work from Elliott and colleagues (2016) has suggested that disruption by irrelevant speech in children is driven by their underdeveloped rehearsal acting as an additional attentional load. Children’s already limited attentional abilities (which reduce their capacity to inhibit irrelevant stimuli) could be further exacerbated by poor rehearsal ability in the presence of irrelevant auditory material thereby

preventing them from accurately recalling items from the focal task. In addition, although Klatte, Lachmann, Schlittmeier et al (2010) did not find a difference in the magnitude of the ISE between adults and children, they observed that children’s poorer attentional control made them vulnerable to a wider range of irrelevant sounds

compared to adults in the study. The youngest children’s recall performance was disrupted by classroom noise while none of the older children and adults were affected by it. These results suggested that children were more vulnerable to distraction and

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memory performance suffered because of irrelevant noises in their learning environment – regardless of whether the noises had a changing-state pattern or not.

The present results concerning the ISE in serial recall were contrary to those of Elliott (2002), Elliott et al. (2016) and Klatte et al. (2010). The present study showed that the ISE was present for adults and children aged 7-9 and 10-11 years old but not for children aged 5-6 years old. These results suggest two implications: First,

developmental improvements in memory strategies and attentional control—which result in memory span improvements—do not necessarily translate into greater resilience to the ISE (Elliott & Cowan, 2005). Second, the rehearsal strategy used to complete a span task in quiet may prove detrimental when used in the presence of irrelevant speech (Elliott & Cowan, 2005). In fact, the results suggest that those age- groups considered to have better rehearsal and attentional control were more susceptible to distraction. Perhaps the increased disruption with age is a reflection of the task design – longer lists for adults than children. Since adults had to remember eight items and children only five, it could be argued that adults were exposed to irrelevant speech for a greater duration than the children and as a consequence show greater disruption by irrelevant speech than children. In terms of the dose of irrelevant speech, this would suggest that individuals who received a higher dose of irrelevant speech (adults) experienced greater disruption to serial recall than those who had a lower dose (children). However, since this comparison is across age groups it is not possible to separate whether the difference seen here was in fact a result of increased dose or rather an effect of age. Therefore, in Study III, the dose of irrelevant speech is varied to ascertain whether children and / or adults are affected by exposure to different amounts of irrelevant speech within a fixed period of time. As will become clear in Study III, the variation in dose did not have an effect on serial recall within and between age groups (see section 4.3). Therefore, in the present context, it would appear that the differences

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are age-related and not due to a higher dose of irrelevant speech for older children and adults.

From a practical perspective, it was commonly observed that schools and classrooms were noisy. Although there is research to show that noise in classrooms has a negative impact on children’s speech and listening comprehension, reading abilities, and long-term recall (Belojevic, Evans, Paunovic, & Jakovljevic, 2012; Hygge, 2003; Klatte, Lachmann, & Meis, 2010; Maxwell & Evans, 2000;), it may be the case that children are more accustomed to working in such environments than adults.

Nevertheless, the overall pattern of results here do suggest that children and adults perform better in quiet than in the presence of irrelevant speech (e.g., Colle & Welsh, 1976; Elliott, 2002).

It was also surprising that the youngest group of children did not exhibit an ISE on serial recall while there was an effect for children aged 7 to 11 and for the adults. It must be noted that the performance of the youngest children was generally lower than the older children and adults; and, the lack of an ISE could be attributed to possible floor effects because baseline scores and performance in irrelevant speech were too low to allow for a differentiation between them. The task for the youngest children was adapted by replacing digits with colour patches, as they were not sufficiently familiar with digits. It is possible that this task modification could have contributed to the lack of effects within this group and lack of developmental difference between this group and others. The study by Klatte and colleagues (2010) has been criticized on the grounds of not placing sufficient demands on rehearsal and attention which in turn reduced possible distraction effects (Elliott et al., 2016). This may have been in the case presently as well – the use of colour patches may have not placed sufficient demands on rehearsal and attention and hence led the absence of an effect.

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The ISE on probed recall and missing-item tasks reflected poorer recall in all irrelevant speech conditions except steady-state speech compared to quiet. This effect was present regardless of age group and is indicative of how irrelevant speech can affect recall on a variety of tasks. The only other study to date to contrast the ISE in probed recall and missing-item tasks among children was Elliott et al. (2016) and the results in the present case are contrary to their findings. In the study by Elliott et al. (2016), children had poorer recall in steady- and changing-state speech compared to quiet (regardless of whether the task necessitated serial rehearsal) while adults showed poorer recall only in steady-state speech versus quiet. This vulnerability of the children to irrelevant speech regardless of its nature and across tasks with and without serial rehearsal, suggested that children were more susceptible to auditory distraction in general than adults. The lack of an age effect with regards to the ISE in the present study suggests that performance in the probed recall task and missing-item task was generally poorer in the presence of irrelevant speech (except steady-state speech)

compared to quiet regardless of whether serial rehearsal was a likely strategy or not. It is possible that a methodological difference between Elliott et al. (2016) and the present study contributed to contrary results. The missing-item and probed recall tasks used in Elliott’s study were alternated in a blocked fashion (e.g., one block of missing-item followed by one block of probed recall). However, in the present study, each task was completed before moving on to the next (the impact of irrelevant speech in the two task designs are compared in Chapter V). The costs incurred by children in task-switching may have contributed to poorer performance compared to adults (Davidson et al., 2006). However, it is clear from the general pattern of results in this study that some findings may be more difficult to interpret within the existing theoretical framework and literature.

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The CS effect.

Serial recall performance is particularly vulnerable to CS speech compared to SS speech (Jones et al., 1992; Jones & Macken, 1993). This effect has been consistently observed in experiments with adults for over four decades and more recently with children as well (Elliott, 2002; Elliott et al., 2016; Hughes et al., 2005; Jones et al., 1993). The effect occurs when two conditions regarding the nature of the task and the nature of the sound are met: the task must involve serial rehearsal and the sound must vary such that each element is different from the preceding one (Jones & Macken, 1993; Jones et al., 1992). Conflict between order information gleaned from automatic

processing of sound and order cues generated from deliberate rehearsal of focal task items lead to the CS effect (e.g., Hughes, 2014; Jones et al., 2010; Jones & Macken, 1995b; Jones et al., 1992). Therefore, the presence of a CS effect in serial and probed recall but not missing-item task provides further evidence that serial rehearsal is needed for the effect to occur (Hughes et al., 2007; Jones & Macken, 1993).

Although the CS effect was present in serial recall overall, it was absent for the 5-9 year old children but present for children aged 10-11 years old and for adults but only when a deviant was present (i.e., for adults, CS + d < SS + d). The present lack of a CS effect for children under ten years of age could suggest that their rehearsal abilities are underdeveloped (Flavell et al., 1966; Garrity, 1975) to such an extent that makes them immune to the CS effect. In other words, 5-9 year old children may not be using rehearsal as much compared to older children, and, therefore have less to gain from rehearsal and less to lose because of its disruption by irrelevant speech (Elliott, 2002). It must be noted, however, that the absence of the CS effect for children aged 7-9 years old is contrary to results from Study I. The difference in results may be attributed to the task designs that were used – the 7-9-year-old children in Study I performed much better in the serial recall task that was adjusted to their span compared to children of the

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same age in Study II who completed a fixed-length version of the task. However, the magnitude of the CS effect in each of these studies was still very low (1% and 2 %, respectively, in Study I and II). This pattern of results suggests that the CS effect is not modulated by task difficulty (Hughes, 2014). A comparison between Study I and II is addressed later in the thesis to show how task design may influence distraction effects (see Chapter V).

The difference between CS + d and SS + d recall scores for the adults can be addressed in relation to the unitary and duplex accounts (Cowan, 1995; Hughes, 2014). The unitary account predicts greater disruption in the SS + d than the CS + d condition because there would be more attention-capturing events in the former than the latter and this pattern should prevail regardless of task-type (Elliott, 2002). However, the duplex- mechanism account predicts an equivalence in disruption by deviants in a SS and CS sequence. The argument follows that since CS and SS sequences (without deviants) are not capturing attention, when deviants are added to the sequences they are the only attention-capturing elements in the sequence. Therefore, so long as the deviants are equivalent, the amount of disruption should be the same regardless of the focal task. Given the theoretical predictions, the pattern of disruption to serial recall in the present case is not the result of attention capture. Taken together with the absence of such disruption in the missing-item task, it appears that poorer serial recall in CS + d compared to SS + d would be best explained as the CS effect. To clarify, the changing- state component of the sequence rather than the deviant element within it is driving the additional disruption in CS + d versus SS + d.

The CS effect on serial recall for the 10-11-year-old children (8.5%) was larger than that for adults (3.4%; though not a statistically significant difference) and may suggest that while they are engaging in rehearsal to assist task performance it may not

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be as sophisticated as the adult strategy of cumulative rehearsal leaving more room for it to be disrupted by irrelevant speech (e.g., Jones & Tremblay, 2000). However, the duplex-mechanism account posits that when rehearsal load increases, children may find it more difficult than adults to focus their attention on the focal task (Elliott et al., 2016). This explanation may apply to the present results given that the 10-11-year-old children were given a fixed list length of 6 items to recall and it may have been challenging for them especially if their memory span was lower than six. If the larger effect for children was due to the their general susceptibility to attentional diversion, then it would be expected that children should experience disruption regardless of the type of irrelevant speech used and the focal task demands (Elliott et al., 2016). However, this was not the case as 10-11-year-old children showed poorer performance compared to quiet in fewer irrelevant speech conditions than adults. While this is surprising it may still indicate that differences in rehearsal efficiency may dictate the level of disruption and although the magnitude of the CS effect was not significantly different between children and adults, the numerical pattern does suggest a larger CS effect for children compared to adults; a pattern that has been observed previously (i.e., Elliott et al., 2016). In addition, the trajectory of results among the children show that the magnitude of the CS effect increased with chronological age – 0.47% for 5-6 year old children, 2.6% for 7-9 year old children, and finally 8.5% for the oldest children.

In summary, the CS effect was, as expected, present in tasks thought to involve serial rehearsal (serial and probed recall but not missing-item). This result supports the view suggesting that the CS effect is reliant upon conflicts between order information in the task and the irrelevant sequence. The analysis of developmental differences showed that the effect was present for the 10-11 year old group but absent for those children under the age of 10 years. Although the developmental differences analysis showed there was no CS effect for the adults, this group did in fact have a CS effect but,

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interestingly, only when deviants were present in the changing- and steady-state

sequences. The general pattern of results suggests that children may be more susceptible to the CS effect than adults, however, in the present study this developmental difference was not statistically significant.

The deviation effect.

The deviation effect is a general distraction effect that occurs regardless of processes needed for focal task performance (Beaman & Jones, 1997; Hughes et al., 2007; Marsh et al., 2017; Vachon et al., 2016) and is the finding that recall in the presence of deviants is lower than in their absence (Hughes et al., 2007; Vachon et al., 2016). Distraction occurs through the mechanism of attentional capture by an

unexpected element in an otherwise stable irrelevant auditory sequence (Vachon et al., 2012). The only prerequisite for this effect to occur is the involvement of attention in the focal task (Hughes, 2014). Klatte et al. (2010) suggested that developmental change would manifest for the deviation effect but not for the CS effect since attentional abilities improve with age (Elliott, 2002; Wetzel, Widmann, Berti, & Schröger, 2006). Therefore, it would be expected that better attentional control would reduce the

likelihood of attention being captured by irrelevant auditory material. From the context of working memory capacity (WMC), it would be expected that that high-WMC individuals would be less prone to attentional capture than those with lower WMC (as has been observed in studies with adults; e.g., Hughes et al., 2013; Sörqvist et al., 2012). This could also be applied to developmental research comparing children and adults as the former would have lower WMC than the latter as their attentional control develops from childhood into adulthood (Cowan et al., 2006; Guttentag, 1997; Hwang et al., 2010; Lane & Pearson, 1982). In addition, it would be expected that older adults would have lower WMC than younger adults considering the cognitive decline that takes place later on in the lifespan (Hasher & Zacks, 1988; Palladino & De Beni, 1999;

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Verhaeghen, Marcoen, Goossens, 1993). Therefore, there is an expectation of greater attentional capture among older adults compared to younger adults. However, research with young (18-30 years) and old adults (60-85 years) have found equivalent levels of attentional capture for the two cohorts even when individual ability was taken into account to adjust sound intensity and task difficulty (Bell & Buchner, 2007; Röer et al., 2015). Although WMC was lower for older adults, this did not relate with greater attentional capture (Röer et al., 2015). Perhaps the difference between the present findings and that of Röer et al. (2015) stems from the use of different deviants – in the present study the deviant was a voice change compared to an item change that was used by Röer et al. (2015).

In the present study, developmental differences analyses suggested that while the deviation effect was present in all three tasks, the presence of the effect did not vary as a function of age. However, this is contrary to individual age-group analyses which showed varied findings regarding the presence (or absence) of the deviation effect. The deviation effect was absent in all tasks for adults and the youngest children. The 7-9- year-old children exhibited a deviation effect on serial recall and missing-item

performance while the 10-11 year old group showed a deviation effect in probed recall (but only when deviants were embedded in a steady-state sequence). It is probable that the developmental differences analysis was unable to pick up on subtle differences among the age groups because for each task there were three out of four age groups that did not exhibit a deviation effect – the lack of a deviation effect for a majority of the sample may have prevented the effect of age from being significant overall. There is evidence, however, among young and older adults to suggest an age equivalence in the deviation effect (Röer et al., 2015). Studies 1 and 2 are the first to incorporate deviant speech sequences in irrelevant speech experiments with children and as such there is no

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previous literature to draw comparisons. Therefore, it may be worthwhile contrasting the deviation effect as seen in Study 1 with the present case.

In the first study, children (aged 7-9 years old) showed a deviation effect in all three tasks. However, adults experienced a deviation effect only in the missing-item task when deviants were in a changing-state sequence. In contrast, the deviation effect in Study II was absent for adults and 5-6-year-old children while it was present for 7-9- year-old (in serial recall and missing-item tasks) and 10-11-year-old children (in probed recall). In Study 1, list lengths for recall were adjusted to individual span scores to ensure that each participant received a recall task matched to their memory span. However, in the present study, span was pre-determined and each age group of participants received a fixed list length for recall. Despite this methodological

difference, children in both studies experienced a deviation effect. A direct comparison of 7-9-year-old children from the two studies showed that children in Study I exhibited a deviation effect on all three tasks – the effect was present regardless of sequence context for the probed recall task but for serial recall and missing-item tasks the effect manifested only if the deviant was in a changing-state context. However, in the latter study, they exhibited a deviation effect only in the serial recall and missing-item task, regardless of sequence context. The adults in Study 1 were immune to the deviation effect in serial and probed recall tasks while exhibiting an effect in the missing-item when deviants were in a changing-state sequence. However, in Study II, they did not show a deviation effect at all.

In Study I, it was suggested that task engagement in the form of rehearsal may have shielded adults from the deviation effect in serial and probed recall tasks (Hughes et al., 2013; Sörqvist et al., 2012). An important distinction between Study I and II was