Measurement of Executive Function in Early Childhood

A Special Issue of Developmental Neuropsychology

Clancy Blair, Philip D. Zelazo, Mark T. Greenberg, Clancy Blair, Philip D. Zelazo, Mark T. Greenberg

• Publisher: Psychology Press
• Year: 2016
• eBook ISBN: 9781135067243
• Topic: Psychology
• Subtopic: Developmental Psychology
• Index: Psychology

During the past decade, a rising interest has emerged in aspects of the broad construct of executive function (EF) in childhood. This has transpired as research has discovered that the development of EF is particularly rapid during early childhood, and that the healthy development of EF appears to play a key role in children's developing social competence and academic and social readiness to attend school. The articles presented in this special issue help advance our understanding of the development of EF, as well as the challenges researchers face when attempting to characterize an aspect of cognition in very young children. Ultimately, this special issue illuminates the many ways in which children come to exhibit age-appropriate levels of social and cognitive competence.

Preschool Children’s Performance in Task Switching on the Dimensional Change Card Sort Task: Separating the Dimensions Aids the Ability to Switch

Adele Diamond

Department of Psychiatry
University of British Columbia, Vancouver
Department of Child & Adolescent Psychiatry
BC Children’s Hospital, Vancouver

Stephanie M. Carlson and Danielle M. Beck

Department of Psychology
University of Washington, Seattle

Correspondence should be addressed to Adele Diamond, Department of Psychiatry, University of British Columbia, 2255 Wesbrook Mall, Vancouver, BC, Canada V6T 2A1. E-mail: [email protected]

Fifty-seven children (53% female) at 3 ages (2½, 3, and 3½ years) were tested on the standard Dimensional Change Card Sort (DCCS) task with integrated stimuli (e.g., a red truck) and on a separated-dimensions version where colorless shapes were presented on a colored background (e.g., a black truck on a red background). Roughly twice as many children successfully switched sorting dimensions when color was a property of the background than when color was a property of the shape itself. Children succeeded 6 months earlier in switching sorting criteria when the dimensions were separated. When evidence of both indecision and accuracy was taken into account, a clear and rich developmental progression emerged. These results support an inhibitory control interpretation of preschoolers’ problems on the DCCS task. Diamond theorized that young children can have difficulty integrating features not part of a single object and separating features of a single object so that the object can be categorized first by one attribute and then by another. Preschoolers remain stuck in thinking about objects according to the objects’ initially relevant attribute (attentional inertia; Kirkham, Cruess, & Diamond, 2003). To switch perspectives, the old way of thinking about the objects must be inhibited. Separating color and shape reduced the need for such inhibition; a truck was always a truck, and the background was always red.

PERCEIVING RELATIONS BETWEEN SEPARATED OBJECTS AND SEPARATING FEATURES OF A SINGLE OBJECT

Diamond has theorized that very young children have difficulty integrating features that are not part of a single object (e.g., relating the color of the background to the shape of an item in the foreground or relating a reward object to a stimulus object; Diamond, Churchland, Cruess, & Kirkham, 1999; Diamond, Lee, & Hayden, 2003) and, the flip side, that very young children have difficulty separating features of a single object (e.g., flexibly reacting to something first in terms of its being a truck and then moments later in terms of its being a red thing; Diamond & Kirkham, 2005; Kirkham, Cruess, & Diamond, 2003; Kirkham & Diamond, 2003). In this article we address the latter—separating features of a single object.

On the Dimensional Change Card Sort (DCCS) task, each card contains a simple drawing of a familiar object (such as a truck or star) in a primary color (Zelazo, Frye, & Rapus, 1996). Children 3 years of age can sort the cards flawlessly by color or shape. When asked to switch from sorting by color to sorting by shape (or vice versa), however, most 3-year-olds do not switch; they continue to sort as they had before. This is striking because the experimenter makes a point of saying that the sorting criterion has changed and before every trial either reminds the child of the sorting rules (e.g., “We are playing the color game now, and in the color game, red ones go here and blue ones go there”) or asks the child where the red ones (or trucks) and where the blue ones (or stars) go, and the child points correctly. Children of 3 years thus err despite knowing and remembering the rules. This was first observed by Zelazo and colleagues (Zelazo et al., 1996) and has been observed in other laboratories in the United States (Kirkham et al., 2003; Munakata & Yerys, 2001), Austria (Kloo & Perner, 2005; Perner & Lang, 2002), Canada (Bialystok & Martin, 2004; Jacques, Zelazo, Kirkham, & Semcesen, 1999; Zelazo, Mueller, Frye, & Marcovitch, 2003), England (Riggs & Williams, 2003; Towse, Redbond, Houston-Price, & Cook, 2000), and Scotland (Rennie, Bull, & Diamond, 2004).

Diamond and Kirkham hypothesized that the difficulty 3-year-olds have in switching from sorting by color or shape to sorting by the other is a difficulty in thinking about the same thing from two different perspectives. Having thought about the primary feature of a truck being its color, it is difficult for 3-year-olds to then flip their mental focus and think about the same item ignoring its color, attending only to its shape. Diamond and Kirkham named children’s tendency to continue to react to a stimulus according to its initially relevant attribute attentional inertia (Diamond & Kirkham, 2005; Kirkham et al., 2003; Kirkham & Diamond, 2003). Three-year-olds quickly become used to focusing on the blueness or redness of a stimulus or on its object-kind property (that it is a truck or a star) and have great difficulty switching the way they think about the stimuli. Once they have focused their attention on one dimension, their attention gets stuck there.

It is not that they fail to realize that something can be both blue and a truck. But, having adopted the mindset that blue things go with the blue model card, they have great difficulty switching to think of a blue truck in terms of its shape and sorting it with the red-truck model card, even though they are told that the correct dimension is now shape. We posit that 3-year-old children’s difficulty lies in disengaging from a mindset (a way of thinking about the stimuli) that is no longer relevant. (Kirkham et al., 2003, p. 451)

Even adults have difficulty when required to switch tasks or dimensions, as the rich literature on task switching so clearly demonstrates (e.g., Allport, Styles, & Hsieh, 1994; Mayr & Keele, 2000; Monsell & Driver, 2000; Rogers & Monsell, 1995; Waszak, Hommel, & Allport, 2003). Adults are able to switch sorting dimensions in the DCCS task, but they show the same pattern in their reaction time (RT) as 3-year-olds show in their accuracy (Diamond & Kirkham, 2005). Their inertial “stuckness” on the first dimension is evident not only in their slower RTs when the sorting criterion changes but in slower RTs on the second dimension (faster RTs on whichever dimension they started with) throughout the testing session (Diamond & Kirkham, 2005).

Evidence from a number of different domains supports the conclusion that children 3 years of age have difficulty thinking about the same thing in two different ways. For 3-year-olds, something is either A or B, but not both (e.g., an object is either a bunny or a rabbit, but not both; Perner, Stummer, Sprung, & Doherty, 2002). Many studies have illustrated this mutual exclusivity bias (Carey & Bartlett, 1978; Markmän & Wachtel, 1988). Remnants of this can be seen perhaps in adults’ difficulty in representing more than one interpretation at a time of an ambiguous figure (Chambers & Reisberg, 1992). For 3-year-olds the problem is more profound: Even when shown the alternatives in an ambiguous figure, many 3-year-olds are still unable to see more than one perspective in the figure (Gopnik & Rosati, 2001). Similarly on appearance-reality tasks (Flavell, Green, & Flavell, 1986), where children are shown something that appears to be one thing (e.g., a rock) but is really something else (e.g., a sponge), 3-year-olds typically say that it looks like a sponge and really is a sponge or that it looks like a rock and really is a rock, but rarely will a 3-year-old give the correct answer that it looks like a rock but really is a sponge. Children 3 years of age can conceive of it as a rock or as a sponge but not as a rock from one perspective and a sponge from another.

It is interesting that 3-year-olds can switch tasks if they do not have to switch the focus of their attention. When the stimuli vary along only one dimension, 3-year-olds can switch from sorting trucks with trucks and stars with stars to sorting trucks with stars and stars with trucks (Brooks, Hanauer, Padowska, & Rosman, 2003; Perner & Lang, 2002). Here, they do not have to change how they are thinking about the stimuli; a truck is always a truck and a star is always a star.

If, however, some trucks (and stars) are yellow and others blue (color varying orthogonally with the relevant dimension [shape]), children of 3 years fail the task (although color is never relevant; Brooks, Hanauer, & Rosman, 2001). Similarly, Shepp and Barrett (1991; Barrett & Shepp, 1988; Shepp, Barrett, & Kolbet, 1987) found that children 4 to 5 years of age seem unable to focus on just the relevant dimension when two dimensions are properties of the same integrated stimuli. However, they found that children could successfully focus on just one dimension, ignoring irrelevant variation in the other, when the dimensions were spatially separated. Spatial separation likewise aids adults’ performance on the Stroop task. Adults find it difficult to switch between naming the ink color and reading the word of integrated Stroop stimuli (color words, such as green, written in the ink of another color, such as red). In that example, the incongruent ink color (red) is an attribute of the word green. Adults perform much better if the incongruent color, although present, is not an attribute of the word itself. Thus, adults perform better when the color and word are spatially separated (e.g., the word is written in black ink with a bar of another ink color above or below the word; Kahneman & Chajczyk, 1983; MacLeod, 1998).

There is considerable evidence that when adults attend to one aspect of an integrated stimulus, they, like children, cannot help but process its irrelevant features as well. For example, Garner and Felfoldy (1970) found facilitation with correlated dimensions and interference with orthogonal dimensions in adults when both dimensions were integral properties of all stimuli. When the dimensions were separated and properties of different stimuli, adults showed neither facilitation nor interference. Ridderinkhof, van der Molen, Band, and Bashore (1997) reported similar results in children 5 to 12 years old using a selective attention task. With integrated stimuli, responses were slowest in the correlated conditions, intermediate in neutral conditions, and fastest in orthogonal conditions. At all ages, responses were slower when the dimensions of color and orientation were integrated than when they were spatially separated. Impressively, Pratt and Hommel (2003, Exp. 4) showed that not only is an irrelevant feature (color) of an integrated stimulus processed by adults but if that irrelevant feature (the same color) then appears as part of a wholly irrelevant stimulus (an arrow), that wholly irrelevant stimulus then influences adults’ performance.

In a manuscript in preparation, Diamond (2005) proposed an “all or none hypothesis”—that the brain, mind, and body initially work at a gross level and only with fine-tuning act in a more differentiated manner. One example is that it is easier to take into account all salient aspects of a stimulus than just its color or just its shape. That is, unbinding (rather than binding) is a problem as far as the properties of individual entities are concerned, as the studies just cited illustrate. Indeed, Schoenfeld et al. (2003) reported evidence at the neural level for rapid, automatic binding. Unbinding would require inhibiting or undoing that process.

INHIBITORY CONTROL IS NEEDED WHEN THE OLD WAY OF THINKING ABOUT THE STIMULI (WHEN ATTENTIONAL INERTIA) MUST BE SUPPRESSED

In accord with Diamond and Kirkham (2005; Kirkham et al., 2003; Kirkham & Diamond, 2003), we contend that inhibition is needed to switch from sorting by color (or shape) to sorting by the other dimension on the standard DCCS because switching sorting criteria requires that the participant flip from thinking about an object (e.g., a truck) first as a blue thing to thinking about it as a truck (or vice versa), and that requires inhibition of the initial mind-set (inhibition of the inertial tendency to continue to attend to the initially relevant attribute, to continue to think about [and react to] the stimuli in the same way one has been thinking about [and reacting to] them). If one is to flexibly switch perspectives (flexibly switch sorting criteria), one must be able to quickly and efficiently inhibit one’s previous perspective and previous stimulus-response mappings.

If, however, one’s old perspective does not need to be inhibited—if one never has to change how one thinks about a truck—then children should be able to succeed on the DCCS task at a younger age. Changing perspectives is required when color and shape are integral properties of the same thing. No change in perspective is required, however, if color is a property of the background rather than of the shape itself. With the dimensions separated, children would never have to think about the trucks (or stars) as anything but trucks and stars and would never have to think about the background as anything but red or blue. We therefore predicted that more 3-year-olds would successfully switch sorting dimensions if color was not an attribute of the stimulus object but instead a property of the background, even though the same colors and shapes would appear on all stimulus cards. In addition to testing our prediction that children of 3 and 3½ years would be better able to switch sorting criteria when the dimensions are separated, we also investigated whether even children of only 2½ years might be helped by the separated dimensions condition.

EARLIER REPORTS OF PRESCHOOLERS’ PERFORMANCE ON SEPARATED-DIMENSIONS VERSIONS ON THE DCCS TASK

There is some disagreement in the literature about whether separating the dimensions only on the sorting cards or only on the model cards is sufficient to help preschoolers succeed in switching sorting dimensions. Mueller (Mueller, Dick, Gela, Overton, & Zelazo, 2004; Zelazo et al., 2003, Exp. 6) tested preschoolers with color and shape separated in a rather unusual way on the sorting cards while remaining integrated on the model cards (using standard DCCS model cards) and found that performance was no better than in the standard condition. Kloo and Perner (2005, Exp. 1) found that separating the dimensions on only the sorting cards greatly increased the number of preschoolers who successfully switched sorting dimensions. Both the Mueller studies and the Kloo and Perner studies found that separating the dimensions only on the model cards did not help; however, studies where the dimensions have been separated on the model cards by providing one model card for each value on each dimension (four model cards) have shown dramatically better switching performance in preschoolers (Rennie, Bull, & Diamond, 2004; Towse, Redbond, Houston-Price, & Cook, 2000).

Only one study, other than the one reported here, has looked at the effect on preschoolers’ task switching performance of separating the sorting dimensions on both the sorting and the model cards. Simultaneously and independently, while our study was underway, Kloo and Perner (2005) tested a separated-dimensions condition where their sorting and model cards contained the outline of a colorless (white) shape on one side of a small, white card and a filled-in colored circle on the other side of each card (see Figure 1). In both a between-subjects study (Exp. 1) and a within-subjects one (Exp. 3), they found that significantly more preschoolers were able to succeed when the dimensions were separated.

Our procedure puts the prediction of better performance in the separated condition to a somewha...

Table of contents

• Cover
• Table of Contents
• The Measurement of Executive Function in Early Childhood
• The Development of Executive Attention: Contributions to the Emergence of Self-Regulation
• Developmentally Sensitive Measures of Executive Function in Preschool Children
• Assessment of Hot and Cool Executive Function in Young Children: Age-Related Changes and Individual Differences
• Executive Function and Theory of Mind in 2 Year Olds: A Family Affair?
• Inhibitory Processes in Young Children and Individual Variation in Short-Term Memory
• Preschool Children’s Performance in Task Switching on the Dimensional Change Card Sort Task: Separating the Dimensions Aids the Ability to Switch