Inhibitory Control in Preschool Children. An investigation of age, gender and socioeconomic differences.

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Inhibitory Control in Preschool Children

An investigation of age, gender and socioeconomic differences

Diamantia Floratou

Submitted as a Master Thesis in Special Needs Education Department of Special Needs Education

Faculty of Educational Sciences

UNIVERSITY OF OSLO

June 2020

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Inhibitory Control in Preschool Children

An investigation of age, gender and Bi socioeconomic differences

Submitted as a Master Thesis in Special Needs Education by Diamantia Floratou

Department of Special Needs Education Faculty of Educational Sciences

UNIVERSITY OF OSLO

June 2020

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Inhibitory Control in Preschool Children. An investigation of age, gender and socioeconomic differences

Diamantia Floratou

http://www.duo.uio.no/

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Abstract

Author: Diamantia Floratou

Title: Inhibitory Control in Preschool Children. An investigation of age, gender and socioeconomic differences

Supervisors: Assoc. Prof. Imac M. Zambrana and Dr. Tone K. Hermansen

Background: Inhibitory control is the cognitive ability to control one‘s attention, behavior, thoughts and/or emotions in order to suppress a prepotent response. In the preschool period it follows a rapid and non-linear development. In particular, studies of children between 3 and 5 years of age have reported that older preschoolers perform better on inhibitory control tasks than younger children. However, studies with Norwegian samples are scarce, in particular studies looking at developmental patterns. Additionally, there are inconsistences in the literature regarding whether there are differences between boys and girls in inhibitory control performance.

Gender differences in favor of girls are more often reported, but the effects are usually small or insignificant. Similarly, the role of socioeconomic background or status (SES) for inhibitory control has more rarely been examined, yet international studies suggests that parental SES is associated with the development of cognitive skills in general. Therefore, it is of interest to investigate whether SES is related to

preschoolers‘ inhibitory skills in the Norwegian context, where the population is becoming increasingly more multicultural and SES gaps are growing. Objectives:

The present study aims to investigate individual differences in children‘s inhibitory control firstly by attempting to answer whether we can replicate the findings of age differences in a sample of Norwegian 3-5-year-olds. Secondly, the study seeks to investigate whether children‘s gender is related to their inhibitory control

performance, and thirdly whether socioeconomic characteristics of parents‘ income and education contribute to variation in the children‘s performances. Methods: A sample of 208 preschoolers (N = 115 girls, 34-71 months) were assessed utilizing a variation of the Day-/Night task by Gerstadt et al. (1994), which is a broadly used tool for measuring inhibitory control in preschoolers, providing different outcome

measures of task accuracy and time spent on the task. Details about parental

socioeconomic status were collected through the Norwegian Statistics Bank (Statistics Norway, 2020). The data were analyzed by conducting a set of hierarchical multiple

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VI regression analyses. Results: As expected, on overall older preschoolers performed better than younger preschoolers on the Day-/Night task. The task showed no

association between gender and preschoolers‘ accuracy scores. A small main effect of gender was, however, found when measuring the time children spent on finishing the task, whereby boys were quicker than girls, even if boys were not found to be

significantly more accurate. There were no main effects of SES (i.e., parental income and education) on the preschoolers‘ inhibitory control performances. However, SES and child gender interaction effects were evident for the time spent on finishing the task, suggesting that girls from higher SES spent an extra amount of time on task.

Conclusion: The study revealed significant improvements in children‘s inhibitory control skills over the preschool period and that boys were faster on the task than girls even if not more accurate. Although, socioeconomic disparities were not related to inhibitory control scores in and of itself, girls from higher SES seemed to be at a disadvantage when it came to time spent on the task. Overall, the Day-/Night task can be a valuable resource of information about the development of children‘s inhibitory control. Results from the task can highlight preschoolers‘ improvement in inhibition with age and might effectively help specialists identify those children who are at risk.

The current study suggests that this task can also be useful in a Norwegian context.

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Acknowledgements

I am deeply thankful to my supervisors Assoc. Prof. Imac M. Zambrana and Dr. Tone K. Hermansen for their invaluable guidance and support throughout this process. I especially want to thank Tone for allowing me to use her research data and for giving me valuable insights into the statistical processes and Imac for her unique ability to explain to me the best possible way to present my research data.

I also want to express my gratitude to my parents (Maria and Pavlos), to my brother Panos and of course to Christos for providing me with support and continuous encouragement throughout my years of study and through the process of researching and writing this thesis. This accomplishment would not have been possible without you.

Thank you.

Oslo, June 2020 Diamantia Floratou

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1. Introduction

Executive Function (EF) is an umbrella term that encompasses cognitive skills necessary for purposeful actions (Miyake et al., 2000). These skills allow us to

monitor and flexibly adapt our behavior to changes in the environment and learn strategies to solve new and complex problems (Ackerman & Friedman-Krauss, 2017).

EFs consist of three core processes; Working Memory, Cognitive Flexibility and Inhibitory Control. Working memory refers to the ability to hold in mind and mentally manipulate information. Cognitive flexibility refers to the ability to think ‗outside the box‘ and adjust to changes. Inhibitory Control refers to the ability to resist impulses, to regulate behavior, thoughts and emotions, and to actively suppress prepotent responses (Diamond, 2013).

Developmentally, the three core components of EFs emerge gradually in early childhood but follow slightly different trajectories that continue until adolescence (Diamond, 2006; Jurado & Rosselli, 2007; Best & Miller, 2010). For example, the development of inhibitory control is notably fast paced early on, compared to working memory and cognitive flexibility with both of the latter trajectories following a slower and more gradual development over the preschool period (Best & Miller, 2010). Due to the rapid and early development of inhibitory control, and its central role for a myriad of cognitive processes, its developmental trajectory has been a central focus for decades (e.g. Dowsett & Livesey, 2000; Montgomery & Koeltzow, 2010; Gagne et al., 2019).

Studies in the Norwegian context that explore children‘s self-regulation in general and inhibitory control in particular are few (see Størksen et al., 2015;

Melinder, Endestad & Magnussen, 2006, for exceptions). Therefore, the aim of the current study is to investigate individual differences in children‘s inhibitory control in a sample of Norwegian 3-5-year-olds, focusing on the role of children‘s age, gender, and socioeconomic background (SES). As a main aim, the study attempts to replicate prior results that show age differences in inhibitory control using the Day-/Night task, a broadly used tool that measures inhibitory control in preschoolers (Gerstadt et al., 1994). Additionally, this study seeks to investigate whether children‘s gender affects their performance on selected outcome measures of the task and whether

socioeconomic characteristics of parent‘s income and education contribute to variation in the children‘s performance.

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2. Theoretical Background

2.1. Executive Functions

Different scientific fields adopt different perspectives on EFs, resulting in various definitions of what the term encompasses (Jurado & Rosselli, 2007). From a developmental perspective, EFs are conceptualized as integral components of

children‘s emerging ability to control and regulate their behavior and attention, delay gratifications and resist impulses (Ackerman & Friedman-Krauss, 2017). EFs are also understood as cognitively oriented processes responsible for supporting goal-directed behaviors (Diamond, 2006; 2013), or put differently, as control mechanisms

responsible for balancing human cognition and action (Miyake & Friedman, 2012).

In the field of neuroscience, EFs have been associated with the frontal area of the brain (e.g. Harnishfeger & Bjorklund, 1994; Diamond, Kirkham & Amso, 2002;

Anderson, 2002), such as the Prefrontal Cortex (PFC), which is a region of the brain orchestrating behavior (Fuster, 2001; Müller & Kerns, 2015). Compared to other regions of the brain, the development of the PFC is relatively slow and continues until late adolescence and early adulthood (Harnishfeger & Bjorklund, 1994; Barbas, 2000). While EFs continue to develop well into adolescence, signs of developing EF abilities are already evident during the first 5 years of life (Diamond, 2006; 2013;

Anderson, 2002; Jurado & Rosselli, 2007). Evidence on the development of EFs in the preschool period comes from tasks designed to measure different EFs across ages (Ackerman & Friedman-Krauss, 2017). Preschoolers‘ performance on many of these tasks improve significantly between ages 3 and 5, but with divergent developmental paths and milestones for the different EF components (e.g. Simpson & Riggs, 2005a;

Diamond, 2006; 2013; Garon, Bryson & Smith, 2008).

It can be challenging to investigate how EF components develop in childhood because they are not always evolving at the same time and they follow different routes (Huizinga Dolan & van der Molen, 2006; Simpson & Riggs, 2005a). Zelazo et al.

(2003; Zelazo & Frye,1998) introduced the Cognitive Complexity and Control (CCC) theory in order to explain why children at different ages fail to perform executive functioning tasks in some situations and not in others. According to the CCC theory, children‘s ability to follow rules, inhibit their prepotent actions and adapt their behaviors in changing situations depends on where they currently are in their

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- 3 - developmental trajectories of each component of EFs. For example, 4-year-old

children can hold more than one rule in mind when inhibiting a prepotent response, which they cannot do at the age of 3 years. Thus, for each developmental transition a new ability is unlocked, and another challenging behavior is ready to be tested at a new level of complexity. In the case of the development of inhibitory control, children show signs of successful performance on inhibitory control measurements even before age 3. Subsequently, a non-linear improvement and a rapid development follows in the next years (Simpson & Riggs, 2005a; Diamond, 2002; Diamond, 2006) with a less dramatic change from age 6 until adolescence (Best & Miller, 2010).

Measurements on EFs can sometimes be affected by the so called ‗task- impurity‘ problem (Miyake et al., 2000), where EF components are intertwined with other cognitive processes. For example, the Stroop task - which is a task with color words printed in the ink of different colors asking individuals to name the ink color rather than the color word (Stroop, 1935) - requires not only inhibitory control but also the ability to read the word. This is a quite demanding process for young children that requires other abilities and can result in distorting the purity of the measurement (Miyake & Friedman, 2012). For this reason, some unique tasks have been designed to measure specific EF components in preschoolers or school-aged children in particular (Carlson, 2005). For example, Gerstadt and colleagues (1994) simplified the adult directed Stroop task by creating the Day-/Night task in order to measure inhibitory control in preschoolers (see below for a detailed description of this task).

Other examples of commonly used measures of inhibitory control are the grass/snow task and the gift delay task (Carlson & Moses, 2001; Carlson, Moses & Breton, 2002).

2.2. Core Components of EFs 2.2.1. Working Memory

In short, working memory is a ubiquitous process of human cognition, (Baddeley, 2010). Working memory requires holding information in mind and mentally manipulating that information. It is a critical component for reasoning, learning, relating information to draw conclusions and translating instructions into actions (Baddeley, 1992; 2012). We use working memory in various daily functions from everyday activities to complex mathematical calculations. Working memory is differentiated from short-term memory, or the process of simply holding information

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- 4 - in mind (Diamond, 2013). The basic component of working memory is the central executive responsible for coordinating attention while performing complex cognitive tasks. It also consists of two subsystems, one responsible for holding verbal and acoustic information (phonological loop) and the other responsible for controlling visual stimuli (visuo-spatial sketchpad) (Baddeley & Hitch, 1994). The two

subcomponents seem to be strongly correlated from early on and the brain structure which sub-serves working memory functions remains constant across the childhood years (Alloway, Gathercole & Pickering, 2006). Developmentally, working memory follows a systematic and slow linear improvement in the preschool period which continues until adolescence (Diamond et al., 2002; Best & Miller, 2010).

2.2.2. Cognitive Flexibility

The term cognitive flexibility - often referred in the developmental psychology literature as ‗shifting‘ (e.g. Garon, Bryson & Smith, 2008; Best & Miller, 2010) - is a cognitive mechanism that helps individuals change perspectives and shift their attention spatially or to somebody else‘s point of view (Diamond, 2013). The term is also connected to the flexibility of the mind to adapt to changes, engage in

multitasking, and in flexible problem solving (Memisevic & Biscevic, 2018). Finally, cognitive flexibility emerges later in development, showing a linear improvement throughout development similar to WM (Davidson, Amso, Anderson & Diamond, 2006; Garon, Bryson & Smith, 2008; Diamond, 2013).

2.2.3. Inhibitory Control

2.2.3.1. Definition and Categorization

Inhibitory control concerns the ability to control one‘s attention, behavior, thoughts and/or emotions in order to override strong predispositions (Diamond, 2013).

Given its multifaceted nature, there have been multiple attempts to better distinguish between the different forms and functions of inhibitory control. Some of the most frequently used taxonomies are outlined below.

Harnishfeger (1995) proposed that inhibition-related functions could be classified according to three dimensions. The first one concerns the intentionality of the inhibition. Intentional inhibition occurs at a conscious level through suppression and control of memory instructions, while unintentional inhibition occurs

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- 5 - subconsciously. The second dimension concerns the functionality of the inhibition by differentiating between behavioral and cognitive procedures of inhibitory control.

Behavioral inhibition is about controlling behavior and impulses, whereas cognitive inhibition involves the control of mental processes, such as suppressing unwanted thoughts and irrelevant information from working memory (Wilson & Kipp, 1998).

The third dimension differentiates cognitive inhibition from resistance to interference, which is a related cognitive process (Kipp, 2005). Both are gating mechanisms that develop with age and support the cognitive ability to ignore irrelevant information.

What differentiates them is that cognitive inhibition is an active suppression process functioning in working memory, whereas resistance to interference functions as a mechanism that prevents irrelevant or distracting information from entering working memory in the first place (Harnishfeger, 1995; Kipp, 2005).

Later on, Nigg (2000), building on Harnishfeger‘s (1995) classification of inhibitory-related processes, distinguished between four processes; cognitive inhibition, interference control, behavioral inhibition and oculomotor inhibition (suppression of reflexive saccades). Thereafter, Friedman & Miyake (2004) based their classification on both Nigg‘s (2000) and Harnishfeger‘s (1995) taxonomies and suggested a distinction between three inhibitory-related functions; prepotent response, resistance to distractor interference and resistance to proactive interference. Noting that there is a plethora of theoretical approaches that places inhibition-related functions into taxonomies, Friedman & Miyake (2004) concluded that the term inhibition has been overextended and researchers need to be more specific when referring to its functions. In the present study, the focus is in particular on behavioral inhibition in children aged 3 to 5 years old, a period with a great amount of behavioral changes, as well as considerable maturation in related brain areas (Diamond, 2013).

2.2.3.2. Measurement of Inhibitory Control

To measure inhibitory control in preschoolers, Gerstadt and colleagues (1994) designed the Day-/Night task. This is a widely known measure of inhibitory control inspired by the Stroop-task (1935), and requires the individual to keep in mind a set of instructions while inhibiting a prepotent response (Montgomery & Koeltzow, 2010).

In the Day-/Night task preschoolers are presented with a set of pictures, and asked to state a given label for each of them. Whenever this label is different from what the

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- 6 - picture illustrates, the child has to suppress their dominant response of labeling the picture by what it represents.

In the original study (Gerstadt et al., 1994), 240 children aged 3.5 - 7 years were tested. The family background of the children ranged from middle to upper- middle class. The task started with the experimenter presenting a set of cards to the children, followed by an instruction of how to respond. The instructions varied based on the following two conditions; in the control condition preschoolers were instructed to say ‗day‘ and ‗night‘ to cards with abstract shapes (see Figure 1a and b), while in the experimental condition children were instructed to say ‗night‘ when seeing card with a sun and ‗day‘ when seeing a card with a moon (see Figure 1c and d). After a brief warm-up session, the experimenter started presenting 16 trials with each card in a randomized order. No rules were repeated and no breaks interrupted the task (Gerstadt et al., 1994).

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Figure 1. Cards used in the experimental condition of the Day-/Night task by Gerstadt et al. (1994).

The results of the study showed that children 3.5 - 4.5 years of age found the experimental condition difficult, whereas the task was easier for 6 to 7 year-olds.

Instead, in the control condition younger preschoolers finished the task with no reported difficulties (Gerstadt et al., 1994), suggesting that younger children did not

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- 7 - find it hard to hold the two rules in mind (i.e., say ‗day‘ and ‗night‘ to cards with abstract shapes). In this condition, the abstract designs did not represent anything in particular and, the children were therefore not requested to inhibit any prepotent response, only to keep the two labeling-rules in mind. Thus, the reason that younger children failed the task in the experimental condition was not due to the increased memory load (Diamond et al., 2002).

In fact, the critical feature that makes the original Day-/Night task difficult is that the actual names of the objects in the experimental condition belonged to one of the correct responses (day or night) regardless of whether the object (stimulus) is semantically related to the response. In practice, the correct response on one trial (e.g., saying ‗sun‘ to a picture of a moon) is the incorrect response on the next trial (e.g., saying ‗moon‘ to a picture of a sun). Therefore, there is an overlap between stimuli (the pictures of a sun and a moon) and responses (saying ‗sun‘ to a picture of a moon and ‗moon‘ to a picture of a sun) which increases the prepotency of the incorrect response (Diamond et al., 2002; Montgomery et al., 2008). Gerstadt et al. (1994) also found a difference in response time (RT) in the two conditions between younger and older preschoolers. Overall, younger children had a slower RT than older children.

The difference in response time was greater in the experimental condition than in the control condition (Gerstadt et al., 1994). In sum, different task manipulations have provided insight into the ways in which inhibitory control develops during the preschool period, and variants of the original ‗Stroop-like Day-/Night task‘ have expanded the practices of measuring inhibitory control among younger children (Diamond et al, 2002; Simpson & Riggs, 2005a; Davidson et al., 2006).

2.3. Gender differences

Many behavioral studies suggest that the development of executive processes follows a similar pace regardless of the child‘s gender (Anderson, 2002; Kochanska, Coy & Murray, 2001). However, neuroimaging studies of the brain systems that control EFs suggest otherwise, i.e., that the brain regions which sub-serve executive processes reach maturity more earlier in girls than in boys (Giedd et al., 1999). Such findings can therefore indicate important gender differences in the preschool period ascribed to biological differences in brain maturation.

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- 8 - In accordance with the neuroscientific evidence, studies show that girls

typically outperform boys on tests of self-regulation (e.g. Ponitz et al., 2008;

Kochanska, Coy & Murray, 2001). Self-regulation is defined as the ability to maintain emotions, motivations and cognitive stimuli into an optimal level (Diamond, 2013). It is typically conceived of a broader concept than EFs. Self-regulation refers to a more general behavior derived from goals and values, while EFs focus on processes related to achievement of a goal (Hofmann, Schmeichel & Baddeley, 2012; Blair, 2016).

Nonetheless, considering its similarities with inhibitory control processes, findings from this branch of studies may support our hypothesis of gender differences in preschoolers‘ inhibitory control skills. For example, in a five-year longitudinal study, Matthews, Ponitz and Morrison (2009) tested a group of preschool children on a self- regulation task and found significant gender differences in favor of girls. Similarly, Wanless and colleagues (Wanless et al., 2013) found that girls had stronger self- regulation than boys. Likewise, a Norwegian study reported gender differences on self-regulation tasks in 5-year-olds (Størksen et al., 2015). Boys scored significantly lower than girls on a behavioral regulation task in which the preschoolers had to touch body parts in an opposite manner from what the instruction said. Based on gender differences detected in studies of self-regulation, it is expected that girls would also outperform boys in their inhibitory control performances in the present study.

The effect of gender differences on inhibitory control is not as evident as in the case of self-regulation and the existing studies are few and contradicting. On one hand, there are studies that report gender differences. For example, in a meta-analysis of gender differences in child temperament, where inhibition was included as one of the 35 dimensions of children‘s temperament, girls outperformed boys on measures of inhibitory control (Else-Quest, Hyde, Goldsmith & Van Hulle, 2006). Similarly, in a study by Memisevic and Biscevic (2018), preschool boys performed poorer compared to girls. In accordance with these results, Klenberg, Korkman and Lahti-Nuuttila (2001) concluded that inhibition and impulsive control mature earlier in girls than in boys, but that this gap closes around the age of six. The above findings are also in line with more classic studies showing that girls performed better on inhibitory control tasks than boys (Kochanska et al., 1996; Kochanska, Murray & Coy, 1997).

On the other hand, there are studies that report insignificant or non-existent gender effects on inhibition as well (e.g. Gerstadt et al., 1994; Montgomery &

Koeltzow, 2010; Chasiotis et al., 2006). In a review by Montgomery and Koeltzow

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- 9 - (2010), which highlighted essential task demands and existing variants of the Day- /Night task, researchers reported no gender differences in the administration of the task (e.g., Chasiotis et al., 2006). Some evidence linking preschoolers‘ developmental changes and gender differences to inhibitory control have also been reported in Norwegian studies (see Størksen, Ellingsen, Wanless & McClelland, 2015; Melinder, Endestad & Magnussen, 2006). Thus, the present study investigates gender as a predictor variable of inhibitory control with the aim of clarifying inconsistencies in the Day-/Night literature.

2.4. Socioeconomic Backgrounds 2.4.1. Definition

SES is a multicomponent construct that includes both economic and social resources (Duncan & Magnuson, 2012). Economic resources are mainly related to the parental income and the material wealth available to children (Rhoades et al., 2011).

Families with greater economic resources have more opportunities to enrich and stimulate children‘s cognitive world than families living in an economically disadvantaged environment (Duncan & Magnuson, 2012). Furthermore, social resources are mainly related to the level of parental education. Parents with high education spend more time with their children, use more complex language when communicating with them, as well as provide more stimulating learning resources and challenging environments (Hoff et al., 2002; Duncan & Magnuson, 2012; Aran- Filippetti & Richaud de Minzi, 2012; Ardila et al., 2005; Hughes & Ensor, 2009).

Children‘s SES background is typically measured by their parents‘ or caregivers‘

resources reported in questionnaires and other personal or public reports (e.g.

Rhoades et al, 2011; Statistics Norway, 2020).

Poverty, which corresponds most closely to the lowest end of the SES continuum, has been found to influence children negatively with regards to many important life outcomes (Blair et al., 2011; Cybele Raver et al., 2013). In particular, the negative consequences of poverty have been suggested to increase the risks for neurocognitive and socio-emotional delays, as well as health disadvantages and behavioral problems (Farah et al., 2006; Fernald et al., 2011). However, Raver, Blair and Willoughby (2013) argue that it is the chronicity of poverty, rather than the

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- 10 - poverty status at a single time point, that matters the most for children‘s development.

Events such as unemployment, crowded households, dangerous neighborhoods and less responsive parenting are risk factors that are associated with poverty and

chronicity of poverty (Fernald et al., 2011). It is expected that the ways in which SES is measured will impact its association with children‘s inhibitory control skills.

2.4.2. Associations between SES and Inhibitory Control

Parental economic status and level of education are two factors highly

associated with children‘s cognitive development (Bradley & Corwyn, 2002). Studies have shown that economic adversity in family environment is associated with low- quality parenting, in terms of disruptions in their behavior towards their children. In addition to that, low-quality parenting is likely to serve as a source of high level of stress for children, which can lead to future development of psychosomatic diseases (Blair, 2010; Blair et al., 2011; Lupien et al., 2001; Neville et al., 2013). These

findings are also supported by several neuroscientific studies indicating that there may be a relationship between SES and the development of brain regions central to EFs (Hackman, Farah & Meaney, 2010; Kishiyama et al., 2009; Noble, McCandliss &

Farah, 2007; Noble, Norman & Farah, 2005).

Studies that directly explore the association between SES and children‘s executive functioning skills, such as inhibitory control, are few. For example, in a study by Turner (2010), parental education is a positive predictor of children‘s performance on the measure of inhibitory control. Contrarily, a lack of caregiving experiences and learning resources in children‘s home environment has been shown to predict a delay in inhibitory control throughout the preschool period (Clark et al., 2013). Findings from the self-regulation and EF-literature also link SES with

inhibition. For example, Størksen and colleagues (2015) investigated the correlation between socioeconomic factors and children‘s self-regulation in a study with 243 5- year-olds measuring parental education and income. Results confirmed this

correlation, but only for girls, adding to the previous studies by Størksen and

colleagues showing that parental education and income are related to children‘s early vocabulary and mathematical skills (Størksen et al., 2015; Størksen & Mosvold, 2013).

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- 11 - Moreover, a synthesis of studies reporting correlations between SES and EFs was published in a recent meta-analysis by Lawson, Hook and Farah (2018). The study strengthened the hypothesis that SES has often been reported to predict

childhood EFs and confirmed the presence of SES disparities in EFs (Lawson, Hook

& Farah, 2018). On the other end, however, there are studies who report no SES- effects on the development of children‘s EFs (Lawson, Hook & Farah, 2018). For example, Wiebe, Espy and Charak (2008) found no SES disparities in measurements of working memory and inhibitory control between preschoolers of higher and lower SES. Such differences in findings indicate a lack of clarity in prior studies of how the SES-inhibitory control association is defined.

Given that SES is a multicomponent construct, it is also natural that different studies, have included different measures of socioeconomic status and that the use of different SES measures can result in varying associations with child inhibitory control. The majority of researchers include economic, educational and/or

occupational factors as important aspects of SES, while others argue for a broader concept including social contexts, physical health, and parenting/neighborhood characteristics (e.g. Bradley & Corwyn, 2002; Mezzacappa, 2004; Noble et al., 2015;

Hackman & Farah, 2009; Sarsour et al., 2011; Holochwost et al., 2016; Lawson, Hook & Farah, 2018). In the present study, children‘s SES background is captured by the average parental income and the completion of higher education for the socio- demographic areas of Oslo in which their childcare center belongs to. Since the investigation of preschoolers‘ socioeconomic background was not part of the study where the Day-/Night task was initially intended, this information was extracted from the Norwegian Statistics Bank (Statistics Norway, 2020a; 2020b; 2020c). The variable selection was limited to parental income and level of education due to a large amount of EF-SES studies focusing on these two variables (Lawson, Hook & Farah, 2018) and the inability to retrieve direct data from the parents.

2.5. Aims of the Thesis

Considering the rapid improvement of inhibitory control in the preschool period, this study aims to investigate whether similar age effects, as previously found in many international studies, are also present in a Norwegian context. Moreover, because there are contradicting views on whether there are significant differences

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- 12 - between girls and boys on inhibitory control skills, a second research question

addresses whether gender is associated with the preschoolers‘ scores. Finally, the third research question addresses the scarcity of research on the relation between inhibition and SES (e.g., Clark et al., 2013), and asks whether SES factors such as parent‘s income and education levels are related to children‘s inhibition scores.

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3. Methods

The present study is part of the ChInfoSeek-project (PI: Assoc. Prof. Imac M.

Zambrana) situated at the Norwegian Center for Child Behavioral Development (NUBU, 2020) and has been approved by NSD (Norwegian Centre for Research Data, ref. number: 55110 / 3 / LAR). The overarching ChInfoSeek-project focuses on the naturally occurring social learning processes that underlie the development of children‘s active information-seeking, how it relates to gender, age and children‘s socio-demographic background, and the impact of this development on learning achievements. The Day-/Night task was included as part of the experimental studies of the ChInfoSeek-project (led by the post-doctoral fellow Dr. Tone K. Hermansen).

The task was originally included to investigate individual factors that contribute to the underlying mechanisms of children‘s information seeking and children‘s ability to reassess an informant‘s claim. In the current study, I use data from the Day-/Night task together with data collected on socioeconomic background to answer questions of the development of inhibitory control during the preschool period.

3.1. Participants

Children were recruited to participate in the study during the fall/winter of 2017 and 2018. The recruitment process started with a letter of consent sent to the children‘s parents, administered through the childcare center. The children themselves were also asked whether they wanted to take part in the study on the day of the

testing. In the case of refusal to take part in the process, children were not subjected to testing, regardless of whether their parents had already accepted their participation in advance. For those cases where consent was obtained, testing was performed with each child individually in a quiet room in the childcare center. The final sample of children who completed the Day-/Night task consisted of 208 preschoolers (N = 115 girls, 34-71 months) out of an initial number of 232. Nineteen children did not manage to finish the test and five children refused to take part in the process, and therefore were excluded from the final analysis.

In order to ensure a diverse socio-demographic sample, children were recruited from childcare centers in eight different districts of Oslo and six municipalities outside of Oslo. The majority of Oslo-based children attended

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- 14 - childcare centers from the northern and western parts of the city (N = 76), while the rest of the children attended childcare centers in the central and eastern part (N = 39).

These two areas are typically considered to be indicative of the families‘

socioeconomic status, where the first group of children has on average a higher parental income and level of education compared to the latter group (Statistics Norway, 2020a; 2020b; 2020c). Regarding the municipalities outside of Oslo, the majority of children were recruited from childcare centers located in northern and western municipalities (N = 52), whereas the rest were recruited from the central and eastern located municipalities (N = 41). These municipalities exhibit similar

socioeconomic background patterns as the Oslo districts, again depicting on average a higher educational level and income for the first group and a lower educational level and income for the second group.

3.2 Measures

3.2.1. Day-/Night task

Preschool children‘s inhibition skills were assessed quantitatively through their performance on the Day-/Night task (Gerstadt et al., 1994). This task requires abilities of memory, shifting and inhibition, although the main focus of the current investigation is on the children‘s inhibition scores. The test procedure and the main variables of interest are presented in the following sections.

3.2.1.1. Procedure

In the current version of the Day-/Night task, children are first told that they will be shown a set of cards and that they have to label these cards according to the following rule: When shown a card picturing a sun, they have to say the word ―sun‖, while they have to say ―moon‖ when they are presented with a card picturing the moon (referred to as rule number one). This first labeling rule requires a certain memory capacity and represents the congruent condition of the task whereas labels and card illustrations correspond. Following the first labeling phase of the task, children are provided with a second rule where they are told that they have to say the word ―sun‖ when they are presented with a card illustrating the moon, and to say

―moon‖ when they are presented with a card illustrating the sun. This latter rule

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- 15 - requires the child to shift from one labeling rule to another. Importantly, as the label and illustration are conflicting, or incongruent, children are required to suppress a prepotent response to label the image on the card in accordance with the illustration, as well as to suppress any inclination to follow the first initial labeling rule. For each condition, children are shown a total of 16 cards, eight of which depict a sun and eight of which depict a moon. Within each condition the order of the cards were presented in a pseudo-randomized order.

3.2.1.2. Inhibitory Control Measures

To measure children‘s inhibitory control, there are several outcome variables to be considered. The first variable of interest is the accuracy score children receive in the congruent condition, ranging from 0 to16 based on the total number of correct answers. Since the congruent condition does not require children to suppress a prepotent response, children‘s score in this condition cannot be used by itself as a measure of inhibition. However, it can be considered as a baseline of children‘s performance when instructed to label cards according to a non-surprising rule (i.e., say ―sun‖ when seeing a picture of a sun), and can thus be combined with other variables. The second variable of interest is the accuracy score children receive in the incongruent condition, also ranging from 0 to 16 based on the total number of correct answers. Because the incongruent score reflects children‘s performance in response to a surprising rule (i.e., say ―moon‖, when seeing a picture of a sun) this score can be a good indication of their ability to withhold a ‗natural‘ or prepotent response. A high score in the incongruent condition is thought to reflect higher levels of inhibitory control.

Most research on the Day-/Night task and variations of the task has measured children‘s inhibitory control using their accuracy score in the incongruent condition, or a total score combining children‘s accuracy in both the congruent and incongruent condition (Montgomery & Koeltzow, 2010; Gerstadt, Hong & Diamond, 1994;

Simpson & Riggs, 2005b; Carlson & Moses, 2001; Tardif et al., 2007). In the

following paragraphs, I will outline some of the reasons why this can be problematic, as well as provide alternative ways of how to measure children‘s inhibitory control through the Day-/Night task.

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- 16 - One problem with measuring children‘s inhibitory control using their accuracy score in the incongruent condition alone is that children‘s accuracy score on the Day- /Night task may fluctuate largely with other cognitive abilities, such as memory and shifting behaviors. An alternative way to measure children‘s inhibitory control using the Day-/Night task is therefore to calculate the difference between children‘s accuracy score in the congruent and incongruent condition (Rasmussen & Bisanz, 2005). This score is calculated by subtracting children‘s performance in the incongruent trials from their score in the congruent trials. In this case, a low score reflects higher levels of inhibitory control. Hence, accuracy difference score can be more informative of children‘s inhibitory control than the total score as it takes into account more general individual differences in children‘s cognitive capacities.

In addition to variables focusing on the accuracy of children‘s performance, another option is to look at the time children need to perform the task in the two conditions. A general assumption would be that children who need more time to perform the task might struggle more to process the task demands. Consequently, children‘s time score in the congruent condition can be considered a baseline of their general ability to respond with a label to a given card. In the incongruent condition however, children‘s time score can be considered a reflection of the degree to which children struggle to inhibit their prepotent response (Bialystok, E. & Martin, 2003;

Montgomery & Koeltzow, 2010; Gerstadt, Hong & Diamond, 1994). Finally, a difference score between children‘s time performance in the congruent and

incongruent condition can also be informative of children‘s inhibitory control. It is calculated by subtracting children‘s time score in the congruent trials from their score in the incongruent trials and can serve together with the above variables, as a potential additional measure of inhibitory control.

In the current study, inhibitory control is investigated using a combination of the above variables, an approach adopted by prior research (e.g. Diamond, Kirkham &

Amso, 2002; Simpson & Riggs, 2005a; 2005b). Specifically, four inhibitory control variables will be used in the analysis; accuracy score in the incongruent condition (Incongruent Accuracy), time performance in the incongruent condition (Incongruent Time), accuracy difference score calculated by subtracting the incongruent score from the congruent score (Accuracy Difference) and time difference score calculated by subtracting the congruent score from the incongruent score (Time Difference).

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- 17 - A point worth mentioning here is that in studies using the Day-Night task, researchers either examine age effects by comparing different age groups or examine age as a continuous variable by identifying correlations between children‘s age and their accuracy score (Montgomery & Koeltzow, 2010). Here, age was included as a continuous measure firstly based on the fact that no significant differences between 3 and 4-year-olds have been found in studies where accuracy scores of different age groups are compared (e.g. Hala, Hug & Henderson, 2003; Bialystok & Senman, 2004;

Rasmussen & Bisanz, 2005). Secondly, in the current study the majority of our sample consisted of 3 and 4-year-olds and then, differences between groups were not expected to be noticeable. Therefore, it was decided to not split the children into groups. Finally, Gender was coded 0=boys and 1=girls. The number of girls who took part in the task was N = 115 out of the total sample of N = 208, indicating a bigger sample size compared to boys‘ N=93.

3.2.2. Socioeconomic Variables

In the current study, information about the socioeconomic background of the individual participants was not available and it was therefore obtained indirectly through collecting data about the overall demography of the area in which the children‘s daycare center is located. The reason why such information was collected indirectly is based on the fact that the SES data were not part of the original study.

Therefore, details about income and education level of the population within the particular area of the child‘s care center were collected through the Norwegian Statistics Bank (Statistics Norway, 2020a; 2020b; 2020c). In particular, information about the median of the total households‘ income for the year of 2018 was collected from each of the eight different districts of Oslo (Nordre Aker, Vestre Aker,

Nordstrand, Gamle Oslo, Alna, Ullern, Søndre Nordstranda and Bjerke / see appendix A, table A1) and for the six municipalities outside of Oslo (Skedsmo, Bærum, Asker, Lier, Ringerike and Lørenskog / see appendix A, table A2). Likewise, the percentage of parents who have attained higher education (more than four years) among the whole population for the year 2018 was collected from the same districts and municipalities of Oslo (see appendix A, table A3 and table A4). A composite score was created combining parent‘s income and education (SES). To create the composite

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- 18 - score, income and education variables were first standardized into Z-Scores (M = 0, SD = 1) and then combined into a composite score (Field, 2016).

3.3. Ethical Considerations

Consideration of the ethics in research with children is an important aspect of research methodology. Four major theoretical perspectives have particular been highlighted as central. The first perspective views children as objects who act without will and are guided by others rather than by themselves. They are described as unable to deal with information and thus in need of protection from adults. The second one is a more child-centered perspective which views children as subjects. According to this perspective, children participate actively in research, such as the tasks they engage in.

However, researchers still have the final say in whether individual children will be included in the research or not, ultimately overshadowing the children‘s initiative (Robinson & Kellett, 2004; Christensen & Prout, 2002).

The third perspective views children as social actors who act on their own accord. They are recognized as autonomous subjects with experiences and

understandings that influence, and become influenced, by the culture and society they live in. Despite this realization, researchers continue to design their methodology without taking into consideration children‘s developmental profile and the social context they come from. Instead methods that fit adults as well are often used. Last but not least, the fourth and most contemporary perspective takes the previous one a little further. Children are still seen as social actors, but they are also viewed as co- researchers who share duties such as choice of topic, the nature of design and the type of methodology (Christensen & Prout, 2002; Farrell, 2005).

Overall, the advancement of research on child‘s development in the twentieth century has changed the way childhood is viewed. Children used to be seen as an incomplete version of adults, whilst the contemporary perspective is that children are competent and active participants is social activities, capable of choosing to

participate or withdraw from the research process. This perspective is also reflected in the current study. To ensure voluntary participation, preschoolers were asked whether they wanted to participate on the Day-/Night task or not.

To gain access to the data on children‘s performance on the Day-/Night task, I have signed a confidentiality agreement with the principal researchers in the

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- 19 - ChInfoSeek-project, Assoc. Prof. Imac M. Zambrana and Dr. Tone K. Hermansen.

Data anonymization and restricted access to data were additional measures taken to ensure confidentiality. The study did not involve exposing the participants to any known risk, nor did it have major implications for the child, either during or after the testing situation. Finally, the data are not considered ‗sensitive‘.

3.4. Statistical Analysis 3.4.1. Data Processing

Children‘s performance on the Day-/Night task is coded according to standard guidelines (Gerstadt et al., 1994; Montgomery & Koeltzow, 2010) and was performed by two individual coders. The first coder was in charge of the data collection and aware of the study‘s research questions and hypotheses, while the second coder was a research assistant blind to such information. Depending on whether children

responded correctly to the current rule or not, they were given a score of zero or one for each of the cards. After coding each trial as correct or incorrect, an accuracy score for the congruent and incongruent condition was created (i.e., adding up children‘s scores from the congruent condition and the incongruent condition), ranging from 0 to 16 for each condition. Likewise, time accuracy (in seconds) for both conditions was calculated from the moment the first card was placed on the table until the last card was labeled by the child.

3.4.2. Missing Data

Before proceeding to the main analyses, cases with missing data were

identified. Out of the total sample (N = 232), nineteen children were unable to follow the rules of the incongruent condition leaving the task incomplete. These cases were classified as ‗missing not at random‘ (MNAR), indicating that the participants performed the task in a different way than what they were asked to (Kwak & Kim, 2017). In the present study, data in the incongruent condition is related to the overall inhibition score and, hence, incomplete data may affect the overall score. In order to decide how to handle the missing data, a dummy variable was constructed with two groups; those who completed the incongruent condition and those who did not. Then a test of between-subjects effects was performed. The ‗eta squared‘ which measures the

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- 20 - effect size of missing data in the sample showed a proportion of 6.3% interaction effect, concluding that missing values are not so critical in the analysis and, therefore, those nineteen cases were excluded from further analyses (Tabachnick & Fidell, 2013).

As a means to ensure voluntary participation, children were asked whether they wanted to participate in the Day-/Night task. This resulted in five children withdrawing from the study out of the initial sample of 232. Based on Kwak and Kim (2017), consent withdrawal is classified into the category of ‗missing completely at random‘ (MCAR) with missing values scattered randomly through the data. If only a few cases have missing data and they seem to be a random subsample of the whole sample, deletion is a good alternative (Tabachnick & Fidell, 2013). Thus, in the present study the five children who withdrew consent upon the day of testing were excluded from the analysis, leaving a final sample of 208 children for the main analysis.

3.4.3. Variable Inspection

First, a preliminary screening was conducted running SPSS Explore analysis.

To examine the distribution of the scores and highlight potential extreme outliers (defined as 3*1.5 Interquartile Range (IQR)), histograms and boxplots were visually inspected for the dependent (Incongruent Accuracy, Incongruent Time, Accuracy Difference, Time Difference) and the independent predictor variables (Age, Gender, SES). Bivariate scatterplots were then checked for linearity between each predictor and outcome variable. Next, investigations for violations of the assumptions of normality and homoscedasticity were executed through different regression models, and finally multicollinearity was inspected through Tolerance and VIF values (Tolerance <.10, VIF > 10) (Tabachnick & Fidell, 2013).

Histogram inspections revealed that the distribution of Incongruent Accuracy was negatively skewed, meaning that the left tail of the distribution was longer than the right tail (Pallant, 2013). In that case, a negative skew indicated that the majority of the sample scored high. However, there were many children who scored low and found the task difficult. Likewise, the dependent variable of Accuracy Difference score was positively skewed, meaning that the right tail of the distribution was longer than the left tail. Here, we see the same pattern in a reverse way, with many

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- 21 - preschoolers having a low accuracy difference score (indicative of high level of inhibitory control), but with still a considerable number of preschoolers with high accuracy difference score (low level of inhibition). Furthermore, the distribution of Incongruent Time was positively skewed, meaning that on average the preschoolers spent less time on finishing the task, although there were still some preschoolers who found the task difficult. Finally, no skewness was detected on the Time Difference variable.

An investigation of violations of the general assumptions of linearity,

homoscedasticity, normality and multicollinearity was then conducted. The outcome variable of Incongruent Accuracy did not seem to show any major violations. There was a linear relationship between each predictor and outcome variable.

Multicollinearity did not appear to be a problem, as the VIF-values were all below 5 and Tolerance was above .10. No extreme outliers (1.5*IQR-3*IQR) were identified (> 3*IQR). Again, for the Incongruent Time score no major violations of the general assumption were reported. The scatterplots indicated almost perfectly linear

relationships between Incongruent Time and the independent variables (Age, Gender, Income and Education) and no multicollinearity was reported. Regarding

homoscedasticity, the spatial patterns of residuals were gathered around zero but were not fairly scattered. This was the weakest point of the assumptions, although it did not appear critical. In addition, there were few outliers, but no extreme outliers were detected (<3*IQR). Furthermore, there were no major violations for the Accuracy Difference score. Although there were some small deviations, the variable had a linear relationship with the predictor variables and can therefore be used in the planned regression analysis. Checking for homoscedasticity, the scatterplots of residuals appear scattered around zero. No problems were detected in values concerning multicollinearity and no extreme outliers were inspected (<3*IQR). Finally, the Time Difference variable did not show any major violations of the general assumptions.

The scatterplots indicated almost perfectly linear relationship and no problems were detected for homoscedasticity, multicollinearity or normality. Although there were some outliers, there were no extreme outliers (<3*IQR).

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- 22 - 3.4.4. Analytical Plan

The aim of the analysis is to investigate whether and how children‘s age, gender and SES affect preschoolers‘ scores on inhibitory control measures of the Day- /Night task. To answer these questions, separate Hierarchical Regressions were

conducted for each dependent variable of interest (Incongruent Accuracy, Incongruent Time, Accuracy Difference and Time Difference).

Each regression model was run according to the same set-up. In the first most basic form of the model, the predictor variables (Age, Gender, SES) were entered stepwise in separate models for each of the dependent variables. Next, to investigate potential interaction effects, all the predictor variables were included as a first step before including the two-way interaction terms (Age X Gender, Age X SES, Gender X SES) as a second step. Finally, the three-way interaction term (Age X Gender X SES) was included as the last step of the model (see Table 1 for an illustration of the procedure).

Table 1.

Order of Entry for Hierarchical Multiple Regression Analyses - Main Analysis.

Model 1

Step 1 Age

Step 2 Gender

Step 3 SES

Model 2

Step 1 Age, Gender, SES

Step 2 Two-way interaction terms (Age X Gender, Age X SES, Gender X SES) Step 3 Three-way Interaction terms (Age X Gender X SES)

Supplementary analysis was performed mainly in the case of a strong

relationship between an outcome and a predictor variable. This is an extra analysis in addition to the main analysis when one predictor variable is highly correlated with one outcome variable (main effect) and we further want to investigate potential interaction effects with the other predictor variables separately. However, regardless of whether we found main effects between an outcome and a predictor variable,

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- 23 - supplementary analyses were also performed in order to examine any potential

interaction combination between the three predictor variables (age, gender, SES) separately. Thus, two independent variables were included as a first step and a pair of two-way interaction terms as a second step (see Table 2 for an illustration of the procedure). All analyses were conducted using IBM SPSS Statistics version 26.

Table 2.

Order of Entry for Hierarchical Multiple Regression Analyses – Supplementary Analysis.

Model 3

Step 1 Age, Gender

Step 2 Age X Gender

Model 4

Step 1 Age, SES

Step 2 Age X SES

Model 5

Step 1 Gender, SES

Step 2 Gender X SES

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- 24 -

4. Results

4.1. Descriptive Analysis

4.1.1. Measurement Outcomes

All children were tested in both the congruent and incongruent condition of the Day-/Night task. The data shows that most preschoolers scored higher in the congruent condition (M = 14.90, SD = 1.49) than in the incongruent condition (M = 12.13, SD = 3.98), although the mean accuracy score in both conditions was high.

The data also revealed that preschoolers needed less time to finish the congruent trials (M = 34.86, SD = 7.13) than the incongruent trials (M = 43.65, SD = 10.00). A

visualization of accuracy scores and time performances are presented in the Figure 2.

Regarding children‘s socioeconomic background, family income was on average 768.880 NOK (SD = 104.446), whereas the percentage of parents with higher education was on average 19.19% (SD = 8.68).

Figure 2. Measurement outcomes in accuracy score and time.

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- 25 - 4.1.2. Bivariate Correlations

Bivariate correlations between all the variables are presented in Table 3. First, the relationship between variables in congruent and incongruent condition is

highlighted here, in order to inspect robust correlations among all the dependent variables of the test. Then the focus is targeted on the outcome variables in order to evaluate whether all three predictors have a critical role to be included in the following analyses.

Given that the Congruent and Incongruent Accuracy scores are part of the Accuracy Difference score (difference between congruent and incongruent accuracy score), we naturally find a strong positive association between these variables. Also, Incongruent Time is strongly associated with both Time Difference score and Congruent Time. However, there is no correlation between Time Difference and Congruent Time. Moreover, there is a strong negative correlation between Congruent Accuracy and Congruent Time, but no correlation between Incongruent Accuracy and Incongruent Time. In this analysis, the focus is on the incongruent variables because they reflect preschoolers‘ inhibitory control skills, whereas the respective congruent ones act as baseline where we can compare outcomes and stress children‘s

improvement of the task through age.

Table 3.

Bivariate Correlations.

¹ ² ³ ⁴ ⁵ ⁶ ⁷ ⁸ ⁹

1 Congruent Accuracy 1

2 Incongruent Accuracy .19^** 1%

3 Accuracy Difference .18^** -.92^** 1%

4 Congruent Time -.26^** -.11& .01% 1%

5 Incongruent Time -.08% -.05% .02% .64^** 1%

6 Time Difference .14^** .02% .02% -.09% .70^** 1&

7 Age .13% .26^** -.21^** -.48^** -.52^** -.22^** 1%

8 Gender .11% .07% -.03% .00% .12% .15^** -.05% 1

9 SES -.16^** -.05% -.00% .19^** .15^** .02% -.28^** -.04 1

**. Correlation is significant at the 0.01 level (2-tailed).

*. Correlation is significant at the 0.05 level (2-tailed)

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- 26 - As expected, there is a significant correlation between Age and the different outcome variables. More specifically, there is a negative correlation between Age and the two dependent variables (i.e., Accuracy Difference and Time Difference scores), meaning that lower scores are associated with older ages. In addition, the dependent variable of Incongruent Time score shows a strong negative association with Age.

This correlation indicates that as preschoolers grow older, their time performance in the incongruent trials improves significantly. Similarly, a positive correlation between Incongruent Accuracy score and Age suggests that preschoolers‘ older ages are associated with higher scores in the incongruent trials.

In this bivariate analysis, there is a small correlation between SES and Incongruent Time score, but not with any of the other outcome measures.

Furthermore, no correlation is detected between Gender and any of the outcome measures. Despite the lack of direct correlation, SES and Gender can still be important moderating factors, and all three predictors are thus included in the following analyses.

4.2. Hierarchical Multiple Regression Analysis 4.2.1. Analysis of Incongruent Accuracy score

Using children‘s Incongruent Accuracy score as the dependent variable, a first model (see left side of Table 4) was run with each of the main predictors added as separate steps. Entered as step 1, Age explained 6.9% of the variance in children‘s accuracy scores. The model revealed that age was a significant predictor of children‘s accuracy scores (F (1, 206) = 15.16, p <. 001). As a second step Gender was included, explaining an additional 0.8% of the variance in children‘s accuracy scores. In

contrast to the age variable, this was not a significant predictor (F (1, 205) = 1.77, p

=.184). Finally, SES was included as a third step, with an additional account of 0.1%

of the variance, but the association was non-significant (F (1, 204) = 0.14, p = .707).

To investigate potential interaction effects, a second model (see right side of Table 4) was run with the three predictor variables (Age, Gender, SES) entered together as a first step, before entering the two-way interaction terms (Age X Gender, Age X SES, Gender X SES), and finally the three-way interaction term (Age X Gender X SES). In this model, the predictors explained 7.7% of the variance in

children‘s accuracy scores (F (3, 204) = 5.68, p = .001), while the two-way interaction

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- 27 - terms explained only an additional 0.9% of the variance, but were not significant predictors of children‘s accuracy scores (F (3, 201) = 0.66, p = .572). Entered as a third step, the three-way interaction term was also non-significant (F (1,200) = 0.03, p

= .856), with no additional contribution to explaining the variance in children‘s accuracy scores (see Table 4 for further details).

Table 4.

Hierarchical regression full mode - Incongruent Accuracy.

Model 1 Model 2

Variable B SE β Variable B SE β

Step 1 Age .114 .029 .262*** Age & Gender & SES .114 .302 .027

Step 2

Age X Gender -.080 .064 -.537

Gender .715 .537 .089 Age X SES .009 .034 .111

Gender X SES -.475 .616 -.084

Step 3 SES .114 .302 .027 Age X Gender X SES -.013 .070 -.116

* p< .05, ** p< .01, *** p< .001.

So far, the analysis revealed that children‘s age was the only significant predictor of their accuracy on the incongruent trials. The strong positive effect of age indicates that older preschooler performed significantly better on the task than younger preschooler. However, from this analysis, we did not find gender or socioeconomic associations with the preschoolers‘ scores which is our second and third aim of the present study. For that reason, we continued our analysis in order to investigate whether there were interaction effects between Gender or SES with children‘s age or Gender with SES. To achieve that, we ran supplementary analyses.

In the third model, the two predictor variables (Age, Gender) entered together as a first step, before entering the two-way interaction term (Age X Gender) as a second step. In the fourth model Age and SES entered together as a first step, before entering the two-way interaction term (Age X SES) as a second step. Last one, the fifth model entered Gender and SES together as a first step, before entering the two-way

Inhibitory Control in Preschool Children. An investigation of age, gender and socioeconomic differences.

Inhibitory Control in Preschool Children

An investigation of age, gender and socioeconomic differences

Inhibitory Control in Preschool Children

An investigation of age, gender and Bi socioeconomic differences

Abstract

Acknowledgements

Table of Contents

1. Introduction

2. Theoretical Background

3. Methods

4. Results