Executive Function

Development Across the Life Span

Sandra A. Wiebe, Julia Karbach, Sandra A. Wiebe, Julia Karbach

• Publisher: Routledge
• Year: 2017
• Print ISBN: 9781138655546
• eBook ISBN: 9781351663236
• Topic: Psychology
• Subtopic: Developmental Psychology
• Index: Psychology

Executive Function: Development Across the Life Span presents perspectives from leading researchers and theorists on the development of executive function from infancy to late adulthood and the factors that shape its growth and decline. Executive function is the set of higher-order cognitive processes involved in regulating attention, thoughts, and actions. Relative to other cognitive domains, its development is slow and decline begins early in late adulthood. As such, it is particularly sensitive to variations in environments and experiences, and there is growing evidence that it is susceptible to intervention – important because of its link to a wide range of important life outcomes.

The volume is made up of four sections. It begins with an overview of executive function's typical development across the lifespan, providing a foundation for the remainder of the volume. The second section presents insights into mechanisms of executive function, as provided by a variety of methodological approaches. The third and fourth sections review the current research evidence on specific factors that shape executive function's development, focusing on normative (e.g., bilingualism, physical activity, cognitive training) and clinically relevant (e.g., substance use, neurodegenerative disease) developmental pathways.

Part I
Characterizing Executive Function Development Across the Life Span

1
EMERGENCE OF EXECUTIVE FUNCTION IN INFANCY

Kimberly Cuevas, Vinaya Rajan, & Lauren J. Bryant

The early building blocks of executive functions (EFs) are acquired during infancy and undergo remarkable improvement during this period. In the span of a few short years, infants become capable of sustaining, shifting, and inhibiting their attention, and eventually use these gains in attentional control to hold and update information in mind and exert control over their behavior in the presence of interfering thoughts and actions. These rudimentary EF skills in infancy likely represent developmental precursors to more complex EFs. In this chapter, we focus on the emergence and developmental progression of EF during infancy. We begin by describing our conceptualization of EF and its foundational components. Next, we detail the tasks commonly used to assess infant EF, highlighting our research and selectively reviewing other work examining the biopsychosocial mechanisms that impact EF development and individual variation. We conclude by proposing future directions for the field, emphasizing both functional and integrative analyses.

Conceptualization of EF

EFs are a set of higher-order cognitive processes involved in coordinating, planning, and completing goal-directed actions (Miyake et al., 2000). Varying theoretical perspectives of EF have emphasized a unitary construct (Duncan, Johnson, Swales, & Freer, 1997), dissociable components (Stuss & Alexander, 2000), or an integrative framework underscoring both “unity and diversity” (Garon, Bryson, & Smith, 2008; Miyake et al., 2000). The structure and organization of EF may exhibit a developmental shift from a single latent EF factor during early childhood (Wiebe, Espy, & Charak, 2008; Wiebe et al., 2011) to separate component processes when children are older (Huizinga, Dolan, & van der Molen, 2006; see Chevalier & Clark, Chapter 2, this volume). Despite these differing perspectives, there is agreement that working memory (WM), inhibitory control (IC), and cognitive flexibility are core EF skills (Diamond, 2016).

Attention also plays an integral role in the development of EF (Garon et al., 2008), and attentional control is viewed as a core component of WM (Kane & Engle, 2002; Reynolds & Romano, 2016). According to Engle and colleagues’ conceptualization of WM (Engle, Kane, & Tuholski, 1999; Kane & Engle, 2002), there is a limited capacity, domain-free executive attention component capable of maintaining short-term memory representations in situations involving interference or response competition. Individual differences in executive attention or “WM capacity” (Kane & Engle, 2002) are predictive of a wide variety of cognitive abilities (Engle et al., 1999). For a more detailed description of the links between executive attention and WM, see Bell and Deater-Deckard (2007).

Our conceptualization of EF is based on Roberts and Pennington’s (1996) framework that emphasizes WM and IC as two core EFs that best represent the role of the prefrontal cortex. WM involves holding information in mind for a brief period of time while actively manipulating that information (Baddeley, 1992). When infants are capable of retrieving a toy from a hiding location after a delay or in the presence of distraction, they are relying on this ability to represent objects in memory. IC involves overriding or delaying a dominant response in order to achieve a goal (Roberts & Pennington, 1996). When infants can forgo reaching for a reward immediately and withhold their response, they are relying on IC to suppress a prepotent response. These two core EF processes work in an interactive function to support goal-directed behavior (Roberts & Pennington, 1996).

Behavioral Development of Infant EF

The measurement of EF during infancy offers particular challenges as tasks must be sensitive to limitations in young participants’ motor skills as well as their receptive and productive language abilities. To meet this challenge, researchers have developed a variety of EF tasks that focus on infants’ behavioral responses (e.g., looking, reaching) during engaging “games”. Table 1.1 provides an overview of some of the most common paradigms used to measure infant EF. In what follows, we provide detailed information regarding delayed-memory search tasks – the most extensively used infant EF paradigm and the focus of our behavioral and psychophysiological research.

Infant Delayed-Memory Search Tasks

The delayed response (DR) task is a widely used nonverbal WM task in human and nonhuman animals (see Pelphrey & Reznick, 2004, for review) that is dependent on the dorsolateral prefrontal cortex (Diamond, 1990b). The Piagetian infant A-not-B task is a variant of the DR task with longitudinal work indicating comparable developmental progression in performance across tasks (Diamond, 1985, 1990b; Diamond & Doar, 1989). In these tasks, participants watch as a desirable object is hidden in one of multiple locations, a brief delay is imposed while participants’ visual attention to the hiding location is distracted (i.e., reducing likelihood of low-level marking strategies), and then participants search (i.e., look, reach) for the object. In the DR task, the hiding location is predetermined (in-dependent of responding); however, in the A-not-B task, after successful search in one location (A; typically multiple times), the hiding location is switched (B). The A-not-B error refers to continued search at the incorrect location (A) on reversal trials (B). Thus, based on the broader animal and neuroscience literature, we conceptualize successful task performance as requiring WM and IC (Diamond, 1990b): maintaining the object location, updating its location between trials, and inhibiting previously rewarded responses. A variety of computational models (see Buss, Chapter 8, this volume) have been developed to understand the processes underlying A-not-B task performance, including different types of memories/processes (active–latent: Munakata, 1998; fast–slow: Thelen, Schöner, Scheier, & Smith, 2001) and conscious representational systems (Marcovitch & Zelazo, 2009). Although a memory process (akin to WM) is included in most accounts, there is debate regarding the need for separate inhibitory processes (Diamond, 2001; Munakata, 1998; Smith, Thelen, Titzer, & McLin, 1999).

TABLE 1.1 Selected Overview of Infant Executive Function Tasks

Task (Examples)	EF Component	Description	Age	Selected References
Antisaccade (Freeze Frame)	IC	Infants are required to inhibit looking to peripheral distractor cues	4 months +	Holmboe et al., 2008, 2010; Johnson, 1995
Delayed-memory search (DR; A-not-B)	WM+IC	Infant must find object in one of multiple locations after a delay, and inhibit searching in previously rewarded locations	4.5 months +	Cuevas & Bell, 2010; Diamond & Doar, 1989; Diamond et al.,1997; Pelphrey et al., 2004; Wiebe et al., 2010
Object retrieval (Barrier Detour)	WM+IC	Infants have to inhibit reaching directly toward object (visible through transparent barrier), reaching instead for side opening while holding the object and alternate route in mind	6 months +	Bell & Fox, 1992; Diamond, 1990a; Diamond et al., 1997; Matthews et al., 1996; Noland, 2008
Prohibition (Forbidden Toy)	IC	Infants are instructed to withhold a prepotent response (e.g., touching desirable object)	8 months +	Kochanska et al., 1998; Miller & Marcovitch, 2015
N boxes/pots (Stationary vs. Scrambled)	WM	N objects are hidden in N containers (stationary or scrambled between trials*). Infant must find each object	12 months +	Bernier et al., 2010; Diamond et al., 1997; Miller & Marcovitch, 2015; Wiebe et al., 2010

Notes
DR = delayed response; IC = inhibitory control; WM = working memory.
* Only the scrambled version is related to dorsolateral prefrontal cortex function (for review, see Diamond et al., 1997).

EF demands of infant delayed-memory search tasks can be heightened by increasing the number of hiding objects/locations, the number of A trials prior to reversal, and the delay between hiding and searching (Cuevas & Bell, 2010; Marcovitch & Zelazo, 1999; Miller & Marcovitch, 2015). Likewise, the A-not-B task with invisible displacement has been used to extend this task into the second year (Diamond, Prevor, Callender, & Druin, 1997; Wiebe, Lukowski, & Bauer, 2010). The procedures are similar, but invisible displacement is considered more challenging because infants do not directly see the object hidden at either location. Additional non-EF factors (e.g., distance between hiding locations; simultaneous covering of hiding locations) can also affect task performance; thus, methodological rigor is critical (Diamond, Cruttenden, & Neiderman, 1994; Marcovitch & Zelazo, 1999). Further, from a dynamic systems perspective, perseverative reaching (i.e., reaching to the incorrect, previously rewarded location) involves “complex interactions of visual input, direction of gaze, posture, and memory” (Smith et al., 1999, p. 253), emphasizing the role of multiple factors in reaching behavior, especially motor planning.

Emergence and Development of EF

Early evidence regarding the emergence and developmental progression of EF came from a series of longitudinal delayed-memory search investigations, in which Diamond tested infants bi-weekly, beginning when they could first reach for a hidden object (Diamond, 1985; Diamond & Doar, 1989). Although there were individual differences in the maximum delay for accurate searches in the A-not-B and DR tasks, there was a general linear trend in performance between 7.5 and 12 months with an increase of 2–3 s per month in the delay required to produce errors in either task. Furthermore, a 2–3 s increase/decrease of the delay for individual infants resulted in perseverative or successful responding.

Looking versions of delayed-memory tasks have been used to extend downward the age of initial assessment. The earliest data come from 4.5–5 months of age, at which time the majority of infants perform poorly (Baird et al., 2002; Cuevas & Bell, 2010; Reznick, Morrow, Goldman, & Snyder, 2004); however, infants older than 5.5 months can maintain the hiding location for 1–2 s delays in a social “peek-a-boo” DR task (Reznick et al., 2004). Within-subjects comparisons of looking and reaching versions of delayed-memory search tasks reveal comparable performance (Bell & Adams, 1999; Matthews, Ellis, & Nelson, 1996; Pelphrey et al., 2004). Figure 1.1 displays the month-to-month performance of a group of infants assessed on both versions of the A-not-B task between 5 and 10 months of age (Cuevas & Bell, 2010).

As can be seen, once infants have developed the motoric skills requisite for the reaching response (8–9 months), performance is overlapping across response modality. Taken together, these findings indicate that by around 8 months, there are substantial improvements in A-not-B performance with about half of infants being able to succeed on reversal trials with a minimal delay (Bell & Fox, 1992; Diamond, 1985). Near 10 months, a basic level of WM and IC is demonstrated with most infants succeeding on reversal trials with minimal delay and some succeeding with longer delays (Diamond, 1985; Matthews et al., 1996). In sum, these findings indicate that the same executive demands are likely required for looking and reaching versions of delayed-memory search tasks.

During the second year, infants continue to exhibit improvements in more advanced versions of the A-not-B task as well as other EF tasks, such as 3-boxes (WM) and forbidden toys (IC) tasks (see Table 1.1; Diamond et al., 1997; Miller & Marcovitch, 2015; Wiebe et al., 2010). However, a recurring finding is the lack of longitudinal stability for individual EF tasks. In addition, unlike findings with children and adults, there is often minimal evidence of consistency across EF measures. As a notable exception, however, Diamond et al. (1997) found similar patterns of age-related change in A-not-B and object retrieval (WM + IC) tasks (see Table 1.1), with performance across tasks being modestly correlated from 8 to 11 months. These findings highlight some of the challenges in measuring EF during infancy, and are potentially related to early emerging executive skills often varying between contexts, yet providing the foundations for the “unitary” structure of EF identified by factorial models during the preschool-age period (Miller & Marcovitch, 2015). Orthogonal to theoretical analysis of the underlying structure of emerging EF, there is consensus that further work is needed to analyze the psychometric properties (i.e., validity, reliability) and increase the precision of measurement of EF throughout early development.

FIGURE 1.1a–b Mean performance (and SE) on the looking and reaching versions of the A-not-B task with incremental delay from 5 to 10 months of age. (a) Mean Object Permanence Scale score. 1–3 = Finding an object partially (1) or completely covered with one cloth (2) or two identical cloths (3). 4–5 = Finding an object in A-not-B procedure with a 0–slight delay (4) or 2-s delay (5). (b) Proportion of correct responses on non-reversal (A) and reversal (B) trials. Error bars represent one standard error. (From Cuevas & Bell, 2010. Copyright 2010 by American Psycholo...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• List of Contributors
• Introduction: Development and Plasticity of Executive Function Across the Life Span
• Part I Characterizing Executive Function Development Across the Life Span
• Part II Understanding Mechanisms of Executive Function Development and Plasticity
• Part III Environmental, Cultural, and Lifestyle Factors That Shape Executive Function Development Across the Life Span
• Part IV Atypical Patterns of Executive Function Development Across the Life Span
• Index