Overview
Source: Laboratories of Nicholaus Noles and Judith Danovitch—University of Louisville
Infants are born with amazing cognitive resources at their disposal, but they don’t know how to use them effectively. In order to harness the power of their brains, humans must develop high-level cognitive processes that manage basic brain functions. These processes make up what psychologists refer to as executive function. Executive function is a key factor in many self-regulatory behaviors, including forming plans to solve problems, negotiating between desires and actions, and directing attention. For example, a child must use several executive processes to stop playing with toys and start cleaning their room. These processes include inhibition (to stop what they’re doing), planning (to determine what actions need to be performed to clean the room), and attentional control (to stay on task until the cleaning is done). A breakdown of executive function during any of these steps would lead to the room remaining dirty.
Developing executive function is one of the key challenges faced by children as they mature. Some elements of executive function can only be mastered with practice, and brain areas linked to executive function, specifically the prefrontal cortex, develop slowly throughout development, continuing to grow and organize until an individual reaches their twenties. Early demonstrations of executive function have been linked to self-control and behavioral outcomes in children, as well as successes later in life. Relatedly, executive function is impaired in children diagnosed with attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorders.
This experiment demonstrates how to assess executive function in children using the Dimensional Change Card Sort Task, developed by Dr. Philip Zelazo and colleagues.1
Procedure
Recruit children between the ages of 3 and 5 with no visual impairment, color blindness, or hearing impairment. For the purposes of this demonstration, only one child is tested. Larger sample sizes are recommended when conducting any experiments.
1. Data collection
- Setup
- Create a set of 16 cards, including 2 target cards and 14 test cards.
- Target cards depict a red boat and a blue rabbit on a white background.
- Test cards are split evenly between pictures of red rabbits and blue boats.
- Place two small trays on a table and affix one target card to each tray.
- Place one red rabbit card and one blue boat card aside. Shuffle the remaining test cards.
- Examine the cards, and reshuffle them if there is a run of more than two cards of the same type (e.g., if there are three or more blue boats in a row).
- Once the cards are pseudo-randomized, place them face down and add the two pre-selected cards on top of the deck.
- Create a set of 16 cards, including 2 target cards and 14 test cards.
- Demonstration phase
- Instruct the child to sit within view of the trays and target cards.
- Label the two target cards by saying, “Here is a red boat and here is a blue rabbit.”
- Introduce the pre-switch rules by saying, “Now, we’re going to play a card game. In the color game, all the blue ones go here, and all the red ones go here.” The experimenter points to relevant target cards.
- The experimenter draws a test card, labels its color aloud (e.g., “This is a blue one, so it goes here”), and then narrates as they place it face down into the appropriate tray as a demonstration to the child.
- Repeat the color game rules.
- Draw a second card, label it, and then ask the child which tray it should go into (e.g., “Here’s a red one. Where does this one go?”).
- Encourage the child to take the card and place it face down in the appropriate tray.
- If the child makes an error in placing the card (e.g., puts it in the wrong tray or indicates the wrong tray), the experimenter should correct them and ensure that the card is placed face down in the correct tray.
- Pre-switch phase
- Tell the child it is their turn and present six pre-switch trials to the child.
- On each pre-switch trial, the experimenter states the pre-switch rules, selects a card, labels the card for the child, and then asks the child to sort the card (e.g., “Here’s a red one, where does it go?”).
- Post-switch phase
- Tell the child, “Now we’re going to play a new game. We’re not going to play the color game anymore. We’re going to play the shape game. In the shape game, all the rabbits go here, and all the boats go here. Remember, if it’s a rabbit, put it here, but if it’s a boat, put it here.” Point to the appropriate tray while stating the instructions.
- Draw the remaining six cards, label them by the relevant dimension (e.g., boat or rabbit), and ask, “Where does this one go?”
- Note that the rules are not repeated in the post-switch phase.
2. Analysis
- Children 3 and older typically sort all cards correctly during the pre-switch phase.
- Use the Dimensional Change Card Sort Task to classify children as either passing or failing.
- A child must correctly sort 5 out of 6 post-switch trials to pass this task. Mean average accuracy on post-switch trials may also be analyzed using an ANOVA to compare performance between age groups.
Developing executive function is one of the key challenges faced by children as they age.
For example, a child must use several executive processes to stop playing with toys and start cleaning their room. Such processes include: inhibition—stopping what they’re doing, planning—the actions needed to clean the room, and attentional control—staying on task until the cleaning is done.
A breakdown of executive function during any of these steps would lead to the room remaining messy.
Importantly, decision-making processes improve across normal development, as associated brain regions—like the prefrontal cortex—mature slowly, well into an individual’s twenties.
This video demonstrates how to assess executive function in children—ages 3 to 5 years—by discussing the steps required to set-up and run an experiment involving the Dimensional Change Card Sort Task, as well as how to analyze the data and interpret the results.
In the Dimensional Change Card Sort Task, children switch from sorting cards by one feature to another. In this case, two target cards consist of a red boat and a blue rabbit and the 16 test cards are split evenly between pictures of red rabbits and blue boats.
This task consists of three phases. During the demonstration phase, each child is introduced to the target cards and the rules of the game. For example, in the color game, all cards of the same color go in the tray with the same color of target card.
Following the demonstration phase, children are exposed to the pre-switch phase—where patterns of thinking and attention are developed by learning to pay special attention to one feature, such as color, and to ignore the other, shape.
Once six test cards are sorted, children move on to the post-switch phase, where the game is changed from color- to shape-sorting.
This phase requires children to shift their attention to a new dimension, which they had been actively ignoring, and to overcome their tendency to perform the same physical actions. The number of correct responses during the post-switch phase trials is the dependent variable.
Three-year-olds typically have a very difficult time transitioning from the first game to a new game because they fail to inhibit their recently learned patterns of thinking and acting.
In contrast, most 5-year-olds do not have a problem transitioning to the new game, which suggests their emerging development of executive function.
Prior to the arrival of participants, make sure a chair and table are set-up with two trays and the target and test cards. Ensure the test cards are pseudo-randomized so that two cards of the same type are not in a row and that the first two cards contain a red rabbit and a blue boat.
After greeting the child, instruct him to sit within view of the trays and target cards. Next, describe the two target cards: Here is a blue rabbit and here is a red boat.
Introduce the pre-switch rules for the color game: Now, we’re going to play a card game. In the color game, all the blue ones go here, and all the red ones go here.
Draw a test card to demonstrate the rules to the child, label its color aloud, and then place it face down into the appropriate tray.
After repeating the rules, pick another card and label it. Then hand the card to the child and encourage him to place it face down in the appropriate tray, and help if necessary.
Following the demonstration phase, introduce the pre-switch rules: select a card, label it for the child, and then ask him to sort it.
Once the child completes six trials, transition to the post-switch phase. Explain the rules now based on shape: Now we’re going to play a new game. We’re going to play the shape game. In the shape game, all the rabbits go here, and all the boats go here.
For the remaining six cards, select one, label it by shape, and hand it to the child for placement.
After the last card has been placed, thank the child for their participation.
To analyze the results, determine the number of correct responses during the post-switch trials for each child in the study and graph the mean results by age group.
A child that scores 80% or more on post-switch trials is said to have passed the Dimensional Change Card Sort Task assessment of executive function. As predicted, on average, the 5-year-olds passed, while the younger 3-year-olds did not, which highlights a critical age for the progression of executive function.
Now that you are familiar with the Dimensional Change Card Sort Task to evaluate children’s executive function, let’s look at other ways that experimental psychologists use it.
Researchers use permutations of this task diagnostically to identify children with particularly poor executive function, which can be indicative of developmental delay or a clinical disorder, such as ADHD or Autism Spectrum Disorder.
In addition, researchers examine decision-making in early adulthood because the prefrontal brain regions are still developing. This lag partly explains how even smart individuals make poor decisions—like choosing the short-term benefits of going to a party over the long-term benefits of studying for a test.
Other researchers have combined the Dimensional Change Card Sort Task and functional magnetic resonance imaging in order to investigate the role of various brain regions in executive function. Findings that suggest age-related differences in connectivity within areas, especially the lateral prefrontal and anterior cingulate cortices, provide insights into the neural mechanisms involved in card sorting performance.
You’ve just watched JoVE’s introduction to the development of executive function using the Dimensional Change Card Sort Task. Now you should have a good understanding of how to setup and perform the experiment, as well as analyze and assess the results.
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Results
In the pre-switch phase of the Dimensional Change Card Sort Task, children are building up patterns of thinking and attention, and those mental activities guide their physical responses. They learn to pay special attention to color, to ignore shape, and to place cards into the relevant trays. The post-switch phase requires children to shift their attention to a new dimension, which they had to actively ignore in the prior task, and to overcome their tendency to perform certain physical actions (e.g., putting the card in the box on the right when it is blue) in favor of an alternative action. Failing to inhibit either the prior focus of their attention or the learned action results in poor sorting accuracy during the post-switch phase.
After learning to complete the pre-switch color game, children’s responses diverge by age (Figure 1). Three-year-olds typically have a very difficult time transitioning from the first game to a new game that uses the same materials but different rules. They fail to inhibit their recently learned patterns of thinking and acting. In contrast, most five-year-olds pass the Dimensional Change Card Sort Task. This success is interpreted as evidence of their emerging development in the domain of executive function.
Figure 1. The percentage of correct test trials completed by each child on average. Children scoring 80% or more “pass” the Dimensional Change Card Sort Task.
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Applications and Summary
The Dimensional Change Card Sort Task is a tool designed to evaluate children’s executive function. The basic version described here can be used to effectively evaluate the executive function of 3- to 5-year-old children. However, there are permutations of this task that can be used to characterize executive function in children up to age 7. This task can also be used diagnostically to identify children with particularly poor executive function, which can be indicative of developmental delay, mental retardation, certain kinds of brain damage, or a clinical disorder, such as ADHD or Autism Spectrum Disorder. Generally, executive function is correlated with problem solving and self- and social-understanding.
Critically, there are many situations where important factors, such as intelligence, diverge from good decision-making. For example, choosing to go to a party instead of studying is a decision that many college students make, even though the short-term fun of a party is obviously less valuable than the long-term payoff of studying. However, the prefrontal cortex, a part of the brain related to executive function, is still developing in college-aged individuals, so it is much easier to understand why even smart young people sometimes make poor decisions.
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References
- Zelazo, P.D. The dimensional change card sort (DCCS): A method of assessing executive function in children. Nature Protocols. 1, 297-301. (2006).
