Running head: Task switching costs in preschool children and adults Task switching costs in preschool children and adults

Past research investigating cognitive flexibility has shown that preschool children make many perseverative errors in tasks that require switching between different sets of rules. However, this inflexibility may not necessary hold with easier tasks. The current study investigates the developmental differences in cognitive flexibility using a task-switching procedure that compares reaction times and accuracy in 4to 6-year-olds to those of adults. The experiment involved simple target detection tasks, and was intentionally designed in a way that the stimulus and response conflicts were minimal, together with a long preparation window. Global mixing costs (performance costs when multiple tasks are relevant in a context), and local switch costs (performance costs due to switching to an alternative task) are typically thought to engage endogenous control processes. If this is the case, we should observe developmental differences with both these costs. Our results show, however, that when the accuracy was good, there were no age differences in cognitive flexibility between children and adults (i.e. the ability to manage multiple tasks and to switch between tasks). Even though preschool children had slower reaction times and were less accurate, the mixing and switch costs associated with task-switching were not reliably larger for preschool children. Preschool children did, however, show more commission errors and greater response repetition effects than adults, which may reflect differences in inhibitory control. Task switching costs in preschool children and adults 1 To negotiate our way adaptively in a dynamic environment, we need to be able to shift and focus our attention appropriately. This ability has been studied in both children and adults, revealing that both groups, depending on the context, can show task switching difficulties, albeit in different performance outcomes (c.f. Diamond & Kirkham, 2005; Kirkham, Cruess, & Diamond, 2003). In adult studies, participants show reaction time costs when switching between relatively simple cognitive tasks (e.g., identifying either a target form or a target color in a sequence of letters). Developmental studies have looked at similar costs in young children in terms of errors or perseverative performance. Indeed, numerous studies have shown that 3and 4-year-old preschool children have great difficulty switching attention between tasks when instructed to do so, but that this ability improves greatly between 5 and 6 years of age (e.g. Carlson, 2005; Cepeda, Kramer, & Gonzalez de Sather, 2001; Chevalier, Sheffield, Nelson, & Clark, 2013; Zelazo, Frye, & Rapus, 1996; Zelazo, Müller, Frye, & Marcovitch, 2003). This line of work has underpinned research showing that the ability to attend selectively and to voluntarily shift one’s attention is central to the development of executive control (Garon, Bryson, & Smith, 2008). However, a number of methodological and conceptual issues limit the conclusions that can be drawn from this work. Firstly, it might seem reasonable to assume that both developmental and adult studies are investigating the same processes, and indeed both lines of research connect their findings to attention and cognitive control. There are, however, important differences in the experimental paradigms that can be used with young children and those used with adults, making direct comparisons difficult. Paradigms developed for young children, such as the Dimensional Change Card Sort (DCCS; Zelazo, Frye, & Rapus, 1996), the Day-Night Stroop task (Gerstadt, Hong, & Diamond, 1994), the Spatial conflict task (Davidson, Amso, Anderson, & Diamond, 2006), and the Shape School task (Blaye & Chevalier, 2011; Chevalier & Wiebe, 2011; Espy, 1997), are normally considered appropriate for preschool children because performance improves to ceiling level across childhood. These tasks traditionally measure perseveration errors and accuracy. However, due to the novel elements in the Task switching costs in preschool children and adults 2 tasks presented to the children (e.g., the lack of feedback, stimulus conflict, etc.), it is not clear that the results are comparable to those of the adult studies. Moreover, in adult studies, switching between two simple and often familiar and well-practiced cognitive tasks produces reliable reaction time (RT) costs, and to a lesser degree, accuracy costs. Thus, it remains unclear whether and how performance on these tasks relate to one another across development. A second major challenge in this domain is the lack of consensus on what the appropriate measures and tasks are for a given age when measuring cognitive control in children (e.g. Best & Miller, 2010; Carlson, 2005). Large individual differences in performance exist, even within a specific age group. Thus, because chronological age is a crude proxy for the level of development, when the performance measure is also crude (e.g., pass/fail), it can be difficult to tease apart age-associated differences from individual differences in attentional control. We know, for instance, that some 3-yearolds can pass the DCCS task whereas some others show great difficulty in shifting attention to the other target dimension. In addition, when presented with a new set of stimuli, among the children who failed the standard DCCS task, some continued to perseverate on the first dimension in the new set whereas others successfully shifted to the new dimension (Hanania, 2010). Potential explanations for the disparate performances among the 3-year-olds are individual differences in either cognitive control and/or other experience-dependent knowledge acquisition, as well as other unspecified situational factors in the experimental context. While it is not clear what best differentiate the subgroups of the perserverators, what is clear is that variability in task-performance often goes beyond what chronological development could account for, and such an observation presents a great challenge to the developmental theory of cognitive flexibility. Thirdly, error-based cognitive tasks are typically only applicable to a narrow range of ages, because of ceiling effect. This is at odds with the fact that cognitive development occurs on a protracted timescale (e.g. Fair et al., 2009; Giedd et al., 1999). In contrast, timed cognitive tasks can be used across a broad age range and are also sensitive to different experimental conditions. Indeed, many Task switching costs in preschool children and adults 3 developmental studies have reported continuous development on simple speeded cognitive tasks such as flanker’s task and Go-NoGo task (Huizinga, Dolan, & van der Molen, 2006; Ridderinkhof & van der Molen, 1995); however, none of these involved task-switching in the preschool years. Thus, the existing literature on cognitive control is limited by a number of methodological concerns. In response to this, the current study will investigate whether a protracted period of development of attentional control is observed when children perform a familiar task with an ageappropriate level of cognitive demand (as is the case in adult study and studies involving older children). In what follows, we first describe the general task-switching paradigm commonly used in adult studies, before turning to a discussion of existing developmental studies of task switching and their current shortcomings. We focus on task switching because it is a very well-studied paradigm in the adult literature that encapsulated the essential elements of cognitive control. The Task-Switching Paradigm The current study is inspired by the task-switching paradigm commonly employed in the adult studies. This paradigm is well-established and involves switching between two simple cognitive tasks, each of which requires attention to a different attribute of the stimuli presented, such as color or form of a letter sequence (Allport, Styles, & Hsieh, 1994; Gade & Koch, 2007; Meiran & Kessler, 2008; Rogers & Monsell, 1995; Rubin & Meiran, 2005). Despite the simplicity of this task, active cognitive control is still necessary for successful performance. Two types of processing costs are commonly reported—global mixing cost and local switch cost. Global mixing costs refer to the between-block differences in reaction times/accuracy when multiple tasks are involved in one block (e.g., mixed block; switching between responding to color and form in the sequence), compared to a block where only one task is involved (e.g., pure block; responding only to color or form). Importantly, these mixing costs are observed even when the participant is repeating the same task from the previous trial in a mixed block, when no attentional shift is required. Local switch costs refer to the within-condition Task switching costs in preschool children and adults 4 differences found by comparing task-switch trials with task-repetition trials in a mixed block, when attention has to be redirected to activate the new task rule and the associated stimulus-response mappings. Task-switching costs across development We focus here only on studies that have measured both RTs and accuracy within a taskswitching context, and further limit our discussion to mixing costs and switch costs associated with task-switching studies. Mixing Cost: Davidson et al. (2006) carried out a series of experiments with task-switching elements on children aged between 4 and 13 years, as well as on adults. Using a spatial incompatibility paradigm, participants had to switch between responding on either the same or opposite side of the screen from the target stimulus, based on the form of the stimuli. The authors reported greater global mixing costs in accuracy for children aged 10 years or younger, than for older participants. However, the accuracy mixing costs appeared as the result of a trade-off with RTs, with older participants showing greater RT mixing costs than younger children. This trade-off effect renders the ove