Qu Finestone Loh Leong reward executive function 2012

Running Head: Rewards and Executive Function in Preschoolers

Revision: Jan 5 2012

Focused But Fixed:

The Impact of Expectation of External Rewards on

Inhibitory Control and Flexibility in Preschoolers

Li Qu1, Dana Liebermann Finestone2,

Loh Jun Qin1, Leong ZhenXia Reena1

1Division of Psychology, School of Humanities & Social Sciences, Nanyang

Technological University; 2 Department of Psychology, University of Waterloo, Canada

Acknowledgement: This research was supported by a grant from School of Humanities

and Social Sciences, Nanyang Technological University to the first author. We thank the

children, parents, daycare centers, and Lim Hui Qing for their assistance in data collection.

Special thanks to the two reviewers and Dr. Koraly Pérez-Edgar, the editor, for their

suggestions on previous versions.

Rewards and Executive Function in Preschoolers 2

Abstract

Promise of rewards has been widely used in controlling preschoolers’ behaviors.

The current study investigated how the expectation of receiving an external reward may

influence preschoolers’ executive function. Four- to 5-year-old Singaporean children were

randomly assigned to reward-informed and reward-uninformed conditions. Results

showed that compared to those in the reward-uninformed condition, although performing

the same on the control tasks and reporting similar motivation and mood states before

being told about the reward, the children in the reward-informed condition performed

better on Day/Night Stroop (Experiment 1, N = 41) but worse on the Flexible Item

Selection Test (Experiment 2, N = 43). These findings suggest that the expectation of

receiving an external reward can influence preschoolers’ behavioral control.

Keywords: rewards, motivation, executive function, attention, inhibitory control,

flexibility, preschoolers

[Word count: 117]


Focused But Fixed:

The Impact of Expectation of External Rewards on

Inhibitory Control and Flexibility in Preschoolers

Executive function (EF) is the internal process required for the conscious control

of thought, emotion, and action (e.g., Zelazo, Qu, & Müller, 2005). As an umbrella term,

EF includes several components, including inhibitory control and flexibility (Lehto,

Juujärvi, Kooistra, & Pulkkinen, 2003; Miyake, Friedman, Emerson, Witzki, & Howerter,

2000). Inhibition is the process required for suppressing irrelevant or inappropriate

responses or response sets, whereas flexibility is the process required for switching or

shifting responses or response sets according to task demands. Tangible rewards can

signal external demands and highlight task goals to individuals (e.g., Schultz, 2000).

Previous work has suggested that external rewards can influence EF in school-aged

children, adolescents, and adults (e.g., Jazbec et al., 2006; Pessoa, 2009). Since EF is still

developing in preschoolers and that preschoolers are reward-seeking (e.g., Zelazo, Qu, &

Kesek, 2010), it is important to investigate how the anticipation of rewards influence

preschoolers’ inhibition and flexibility.

Expectation of Rewards, Motivation, and Executive Function

The motivation of earning a reward can enhance task performance. For instance,

the expectation of rewards can reduce adults’ reaction time during go trials in the Stop

Signal Task (Locke & Braver, 2008), enhance cue-related task preparation and reduce

switch costs during task switching (Savine & Braver, 2010), a pattern that has also been

reported in school-aged children and adolescents. Jazbec and colleagues (2006), using a


monetary reward antisaccade task, found that the expectation of rewards improved

adolescents’ performance accuracy. Consistent results have also been reported in 7- to 17-

year-olds via the continuous performance task, Go/No-go, and the Stop Signal Task

(Kohls, Peltzer, Herpertz-Dahlmann, & Konrad, 2009; Sinopoli, Schachar, & Dennis,

2011; Smith, Halari, Giampetro, Brammer, & Rubia, 2011).

This is possibly because the motivation of earning a reward can facilitate

attentional control and executive control. Rewards have been shown to increase signal

detection (e.g., Engelmann & Pessoa, 2007; Small et al., 2005), selective attention (e.g.,

Padmala & Pessoa, 2011; Savine & Braver, 2010), and sustained attention (e.g.,

Engelmann, Damaraju, Padmala, & Pessoa, 2009). Similarly, the expectation of rewards

can increase attentional control in primary school children. For instance, in a spin-wheel

game in which children can win rewards depending on which words the pointer stops on,

6- to 10-year-olds looked at the words associated with rewards for a much longer period of

time compared to those associated with punishments or neutral objects (Nunnally,

Duchnowski, & Parker, 1965). Additionally, the expectation of rewards can increase

inhibition. For instance, in Padmala and Pessoa’s (2011) study, participants were asked to

respond to images only and ignore conflicting overlaid words. They found that

performance improved with rewards. Furthermore, the expectation of rewards can increase

task preparation and improve flexibility (Savine & Braver, 2010). Indeed, Smith and

colleagues (2011), using event-related functional magnetic resonance imaging (fMRI),

found that among 10-43-year-olds, anticipation of rewards increased activation in the

inferior and ventromedial prefrontal cortices, striatum, and temporo-parietal regions,

which are related to executive control and reward processing.


Conversely, the expectation of rewards can impair task performance as well. For

instance, in the Stop Signal Task, participants motivated by rewards associated with the

go-trials took a longer time to withhold their responses during stop-trials (Padmala &

Pessoa, 2010). Similarly, in a color-naming Stroop task, Krebs, Boehler, and Woldorff

(2010), pairing a subset of ink colors with monetary incentives, found that although their

performance of naming these colors was improved, participants’ ability to ignore the word

format of these rewarded colors decreased. Perhaps these studies used two tasks that were

in conflict with each other. Rewards may increase the performance on the target task while

impairing the performance on the conflicting secondary task.

Expectation of Rewards, Mood, and Executive Function

The expectation of rewards may make participants feel happy, which can improve

task performance. For example, school-aged children in a positive mood state were more

able to solve the Duncker candle creativity test (Greene & Noice, 1988). Previous research

has shown that positive mood can increase attention breadth (e.g., Fredrickson, 2001;

Rowe, Hirsh, & Anderson, 2007), as well as semantic association (e.g. Ashby et al., 1999;

Rowe et al., 2007). In addition, positive mood may increase inhibitory control. For

instance, Seeman and Schwarz (1974) reported that 9-year-olds in a positive mood were

more able to resist immediate rewards and wait for a delayed large reward, compared to

those in neutral or negative moods. Additionally, positive mood can enhance flexibility.

For instance, people in a positive mood are less susceptible to perseveration in measures

of task switching (e.g., Dreisbach & Goschke, 2004). According to the neuropsychological

theory of positive affect (Ashby et al., 1999), mildly positive mood leads to phasic

increases in dopamine in the ventral tegmental area and substantia nigra, which have


projections into the striatum and prefrontal cortex, including the anterior cingulate cortex.

Therefore, mildly positive mood facilitates functions that depend on these brain regions,

such as reward seeking, goal-setting, rule selection, rule use, and flexibility.

At the same time, positive mood can also impair performance. For example, people

in a positive mood were less able to maintain or update information (e.g., Seibert & Ellis,

1991), and were more distracted in the Stroop task (e.g., Phillips, Bull, Adams, & Fraser,

2002) and the Flanker task (Rowe et al., 2007). Additionally, people in a positive mood

were less able to make a concrete plan in the Tower of London or engage in deductive

reasoning (e.g., Oaksford et al., 1996), and they tended to generate more task-irrelevant

thoughts (Seibert & Ellis, 1991). This is possibly because positive mood can increase the

scope of both selective attention and semantic association (e.g., Rowe et al., 2007). This

kind of change can improve performance when it is relevant to the target task, but may

impair performance if it is irrelevant to the target task.

Dual Competition Framework

Taken together, expecting a reward can facilitate EF, possibly via motivation and

mood, which results in the enhancement and impairment of performance depending on the

task. Pessoa’s (2009; Pessoa & Engelmann, 2010) dual competition framework provides a

useful outline to integrate the research reviewed above. This framework is based on the

general assumption that cognitive resources are limited, and that various cognitive

activities thus compete with one another for these resources (e.g., Norman & Bobrow,

1975). According to Pessoa (2009; 2010), in terms of processing information, there is

competition at the perceptual level as well as executive level. Emotional stimuli, mood,


and motivation, including the expectation of rewards, integrated with EF, can influence

the allocation of resources to achieve more efficient goal-directed behavior at both levels,

via stimulus-driven and state-dependent effects. Whether performance is enhanced or

diminished depends on task relevance and the intensity of the affect. When the content of

emotion, mood, or motivation is related to the task and when the level of the affect is low

or mild, in general, performance generally improves. However, if the content of emotion,

motivation, or mood is in conflict with the task at hand, or if the affect is intense,

performance is impaired.

The dual competition framework (Pessoa, 2009) suggests that when rewards are

mild and task-relevant (i.e., when participants are told that they would receive a reward if

they perform well), motivation for the reward may increase the allocation of cognitive

resources for task relevant functions both at attention level and executive level. This in

turn may increase the performance of the target task. Indeed, the research reviewed above

supports this hypothesis. However, it remains unclear whether this is true for preschoolers.

Developmental Features of Preschoolers

Although developing rapidly, compared to school-aged children, adolescents, and

adults, the EF of preschoolers is immature (Zelazo et al., 2005). First, the ability to

regulate attention is still developing in preschoolers. According to Hanania and Smith

(2009), the attentional control of preschoolers develops in three stages: “from more graded

to more categorical perceptual discrimination, from more imperfect to more all-or-none

selective attention, and from ‘sticky’ attention to the flexible switching of attention from

one dimension to another” (p. 631). In other words, preschoolers who are able to

discriminate targets from distractors may still fail to inhibit their response to these


distractors, and preschoolers who are able to inhibit the tendency to attend and respond to

distractors may still fail to flexibly switch attention and response sets between targets. For

instance, using the Dimensional Change Card Sorting (DCCS; Zelazo, Műller, Frye, &

Marcovitch, 2003), in which children are asked to sort cards first by one dimension (e.g.,

shape) and then switch to sort cards by the other dimension (color), researchers have

shown that directing preschoolers’ attention to the first dimension (for example by

labeling the first dimension) can impair rather than improve their switching to the second

dimension (e.g., Munakata & Yerys, 2001; Zelazo, Frye, & Rapus, 1996).

Preschoolers are also in the process of developing inhibitory control. For example,

in Day/Night Stroop (Gerstadt, Hong, & Diamond, 1994), a simplified Stroop task

(Stroop, 1935), children are asked to say “night” when they see pictures of the sun and say

“day” when they see pictures of the moon and stars. Four- to five-year-olds have difficulty

suppressing the default association of day-sun, and activate the new association of day-

moon, though they are able to establish the association between day and an abstract design

and name “day” upon seeing the design (Gerstadt et al., 1994).

Preschoolers also lack the ability to switch between responses flexibly. For

example, in the Flexible Item Selection Task (FIST; Jacques & Zelazo, 2001), which is

similar to Wisconsin Card Sorting task (Milner, 1963), except it is simpler and children

are supposed to engage in switching by themselves instead of switching based on

feedback, children are shown a set of three pictures of objects with different colors,

shapes, or sizes. For instance, they are shown a small red boat, a small yellow boat, and a

small red teapot. Children are asked to group the pictures in two different ways. Although

during the first trial, 4-year-olds can easily group a small red boat and a small yellow boat


together based on shape dimension, most of them are unable to choose different pictures

based on a different dimension during the second trail. Instead of grouping the small red

boat with the small red teapot according to color dimension, they stick with matching by

the shape dimension, choosing the small red boat and the small yellow boat again.

Furthermore, preschoolers are not good at integrating subordinate goals into a

hierarchical comprehensive goal system, especially if the subordinate goals are in conflict

with each other (Bunge & Zelazo, 2006; Zelazo et al., 2003). For instance, in the FIST, the

final goal is to group pictures in two different manners and the two subordinate goals, for

example, are to group two pictures based on shape dimension, and to group two pictures

based on color dimension. However, due to the fact that the two subordinate goals are in

conflict with each other (i.e., to group pictures based on color dimension, children need to

stop thinking these pictures from the perspective of shape), most 4-year-olds are only able

to achieve the first subordinate goal and fail to accomplish the main goal (Jacques &

Zelazo, 2001).

However, preschoolers are responsive to emotional stimuli and rewards (Zelazo et

al., 2010). For instance, Isen (1990) found that 3-year-olds who received an attractive gift

prior to completing a seriation task (nested cups) correctly nested 2.63 cups, whereas

children who did not only nested 1.48 cups. In addition, children in the positive mood

condition were more likely to turn the cups upside down and stack them as towers,

revealing an increase in representational flexibility. Additionally, Qu and Zelazo (2007)

have found that preschoolers appear to be more flexible when happy faces are used as

stimuli in the DCCS instead of neutral objects. Similar results were reported by Wong,

Jacques, and Zelazo (2009) with the FIST. This is possibly because human faces attract


children’s attention (e.g., de Haan, Humphreys, & Johnson, 2002). Additionally, happy

faces may make preschoolers feel mildly happy and hence increase their attention scope

and their flexibility (Ashby et al., 1999).

Nevertheless, unlike adults, preschoolers tend to engage in simple automatic

processing while facing hot attractive rewards. The desires to have attractive rewards can

impair children’s EF (Zelazo & Műller, 2002; Zelazo et al., 2010; Zelazo et al., 2005). For

example, in the Delay of Gratification task, in which children are given a choice of having

one marshmallow now versus two marshmallows later, marshmallows are presented to

children as the goal of their behavioral regulation and the external reward (e.g., Mischel &

Ebbesen, 1970). In this type of situation, the majority of 3-year-olds cannot resist the

temptation of the targets/rewards and tend to choose immediate though smaller rewards.

They behave even more impulsively if they are directed to focus on the arousing qualities

of the reward, such as the taste of a marshmallow (Mischel & Baker, 1975). If the

attractive tangible rewards were removed, and instead, 3-year-olds were presented with

symbolic and neutral stimuli (pictures of an elephant and a mouse), their performance

improved (Carlson, Davis, & Leah, 2005). These results suggest that desires for attractive

rewards can impair children’s inhibitory control. Rewards can also decrease flexibility in

children. For instance, Lepper, Greene, and Nisbett (1973) told the preschoolers that they

would receive a prize after they finished drawing. Although these children drew similar

numbers of pictures, their drawings were less creative, compared to those who were not

told about receiving a prize.

In sum, similar to older children and adults, preschoolers are reward-driven, and

their affect can influence their attentional control and executive control. However, unlike


adults, preschoolers are immature to regulate emotional stimuli, control attention, inhibit

irrelevant responses, switch between response sets, and establish a hierarchical goal

system to integrate conflicting subordinator goals. Hence, it is unclear whether expectation

of rewards may improve EF in preschoolers.

The Current Study

The current study investigated how the expectation of rewards may influence EF in

preschoolers. In particular, the impact of rewards on inhibitory control and flexibility were

examined. To measure inhibitory control, in Experiment 1, Day/Night Stroop (Gerstadt et

al., 1994) was used. This task has been shown to correlate with other inhibitory control

tasks such as the Bear/Dragon task, a simplified version of “Simon Says” (Carlson &

Moses, 2001). To measure flexibility, in Experiment 2, the FIST (Jacques & Zelazo, 2001)

was used.

In each experiment, a between-subject design was used. Children were randomly

assigned to a reward-informed and a reward-uninformed condition. To control for

individual differences, before the motivation manipulation, children’s vocabulary (the

Peabody Picture Vocabulary Test – III; Dunn & Dunn, 2006), short-term memory (Block

Span; Stanford-Binet Intelligence Subtests, Fifth Edition, SB-5; Roid, 2003), inhibitory

control (Bear/Tiger, modified Bear/Dragon; Carlson & Moses, 2001), flexibility (DCCS;

Frye, Zelazo, & Palfai, 1995), understanding of mental states (Flavell, 1986), and

motivation and mood states were examined.

To help children feel comfortable and encourage their cooperation, we played,

together with the children, with various toys, ranging from slightly broken to mildly

attractive, for five minutes before conducting any tasks. Then during cleaning up, we


asked the children to sort these toys based on their preferences. Children put the relatively

attractive toys into a good-toy box, and the relatively unattractive toys into a bad-toy box,

and neutral toys into an OK-toy box. To avoid altering their mood states, we did not give

them any rewards before the target tasks. To prevent children from being distracted, we

did not present any rewards to them during the target tasks.

Only the children in the reward-informed condition were told about rewards. To

manipulate their expectation of rewards, we used a performance-contingent manipulation

(e.g., Kohls et al., 2009; Locke & Braver, 2008; Savine & Braver, 2010; Sinopoli et al.,

2011) and told them that, if they performed well, they would receive a toy from the good-

toy box that was similar to the toys that they played with earlier.

It was hypothesized that the expectation of receiving a toy can motivate children.

This motivation can increase children’s attention orientation and selective attention.

Children become more focused and more able to filter irrelevant information. When the

inhibition of irrelevant responses is the main function prioritized in the target task,

enhanced selective attention and inhibitory control should improve children’s performance

on the target task. In Experiment 1, Day/Night Stroop (Gerstadt et al., 1994), a task

requiring suppression of default association, was used as the target task. Hence, we

expected that children who were promised a reward should perform better on Day/Night

Stroop compared to those who were not told about the rewards.

In Experiment 2, the FIST (Jacques & Zelazo, 2011), a task that requires flexibility,

was used as the target task. Similar to Day/Night Stroop (Gerstadt et al., 1994), while

grouping two pictures together in the FIST, children need to selectively focus on the

relevant dimension and pictures while ignoring the irrelevant dimension and pictures.


However, unlike Day/Night Stroop (Gerstadt et al., 1994), in addition to selective

attention and inhibition, flexibility is required in the FIST (Jacques & Zelazo, 2001). After

grouping two pictures according to one dimension, children need to switch mental sets and

group pictures according to a different dimension. Furthermore, as reviewed above, young

preschoolers often fail to integrate the two conflicting subordinate goals into the essential

main task goal. They tend to focus on the first subordinate goal and fix their mental set on

the first dimension, and thus fail to switch to a different dimension. While expecting a

reward for good performance, preschoolers may become even more focused on the first

subordinate goal and more fixed their mental sets on the first dimension compared to those

preschoolers with no knowledge of the rewards. Additionally, preschoolers are less able to

switch attention or view broadly when their attention is directed and becomes focused

(Hanania & Smith, 2010). Hence, we expected that the anticipation of a reward should

impair preschoolers’ performance on the FIST.

Experiment 1

Method

Participants. Forty-seven Singaporean preschoolers (M = 53.5 months, SD = 6.9,

Range: 43 - 69; 24 girls) of Chinese, Malay, and Indian decent participated in this

experiment. For all participants, parents were provided with a written description of the

experiment, and they granted informed consent allowing their children to participate. Due

to ethical consideration, children who reported “I feel like crying” (i.e., very upset) on the

Mood Check Scale or “I do not want at all” on the Motivation Check Scale during the first

or second motivation and mood check were not given the remaining tasks (n = 5).


Materials.

Day/Night (Gerstadt, Hong, & Diamond, 1994). This is a Stroop-like task in

which children were first asked about the association between the sun and the day,

between the moon and the night. Then children were told to play a silly game in which

they were going to say “day” when they saw a picture of a moon and stars, and to say

“night” when they saw a picture of a bright yellow sun. There were two practice trials and

16 test trials. In addition, the total time for children to complete all 16 trials was recorded

as the total response latency. The stimuli were illustrated and printed in a book format.

Mood Check Scale. Five cartoon faces that were very happy, happy, neutral, upset,

and crying were presented on a piece of paper. Children were shown the scale and told:

“Here I have some faces. You see, this one is laughing, this one is smiling, this one is

looking, this one is unhappy, and this one is crying (the face order was presented

randomly). Yes, this one feels very happy, this one feels happy, this one feels OK, this one

feels upset, and this one feels very upset”. Then children were asked “How do you feel

now? Which one feels the same as you do?” Participants were asked to point to the

stimulus that most closely corresponded to their mood. Their response was scored by

using 1–5 scales, where 1 indicated the positive end of the scale (e.g., very happy), and 5

indicated the most negative point on the scale (e.g., very upset). This scale was

administered by Experimenter 1.

Motivation Check Scale. Five cartoon boys (or girls) using arms and hands to

display how much they want to play the games were presented on a piece of paper. In the

“I really really want” cartoon, the character uses arms to show the distance by opening up

the arms open to almost 180 degree. In the “I really want” one, the character opens up the


arms to almost 60 degree. In the “I want only a little bit” one, the character uses hands to

show the distance by leaving a hand distance between its two hands. In the “I want only a

little little bit” one, the character uses two fingers, leaving a small distance between two

fingers. In the “I do not want at all” one, the character holds its arms together. After

explaining the gestures to the children, participants were asked to point to the stimulus that

most closely corresponded how much they wanted to play the games. Their response was

scored by using 1–5 scales, where 1 indicated the positive end of the scale (e.g., I really

really want), and 5 indicated the most negative point on the scale (e.g., I do not want at

all). This scale was administered by Experimenter 1.

The Peabody Picture Vocabulary Test–III (PPVT, Dunn & Dunn, 1997). This

test is a measure of receptive vocabulary. The experimenter read aloud a word, and

children were asked to select the picture that best illustrated what the word referred to

among a set of four pictures. The task continued until children had reached an error rate of

at least 75% on the last 12 words.

Block Span (Stanford-Binet Intelligence Subtests, Fifth Edition, SB-5; Roid,

2003). This task measures the development of short-term spatial memory. Children were

asked to tap certain blocks after the experimenter. Children were scored according to the

number of blocks that they were able to tap in the correct order. For any given number of

blocks, children were given 3 trials. The task was discontinued if children made 2

mistakes out of 3 trials.

Bear/Tiger. This task is a modification of the Bear/Dragon task (Carlson & Moses,

2001). Children first were asked to perform 10 actions such as “touch your ears” and

“clap your hands.” Following this children were introduced to two puppets, a “nice Bear”


and a “naughty Tiger.” Children were told that they should follow directions given by the

nice Bear but not those directions given by the naughty Tiger. After practice, children

were given 10 test trials (i.e., 5 Bear trials and 5 Tiger trials in an alternating order).

Children’s scores were based only on the Tiger trials. The scores ranged from 0 to 3 on

each Tiger trial (0 = a full commanded movement, 1 = a partial commanded movement, 2

= a wrong movement, 3 = no movement).

Card Sorting. This task is a modification of the DCCS (Zelazo et al., 2003), which

is a measure of rule switching. Children were asked to sort cards that can be sorted by two

dimensions, color or shape. During pre-switch phase, children were told to sort the stimuli

cards according to one dimension (e.g., color). If children successfully sorted 5 out of 6

trials during pre-switch phase, children were scored as having “passed” the pre-switch and

were given post-switch test, in which they were told to sort the stimuli cards according to

the other dimension (i.e., shape). If children successfully sorted 5 out of 6 trials during the

post-switch phase, children were scored as having “passed” the post-switch and were

given post-post-switch test, in which they were asked to sort the stimuli cards according to

the previous dimension (i.e., color). If children successfully sorted 5 out of 6 trials during

the post-post-switch phase, children were scored as having “passed” the post-post-switch.

Appearance-Reality. This measures children’s understanding that what an object

appears to be may be different from what the object really is. Two versions of the

Appearance-Reality task (Flavell et al., 1983; 1986) were used. In the identity version,

children were shown a piece of soap which looked like a rock. In the color version,

children were shown a green paper clip in a red glass, which appeared to be black instead

of green. In each version, children were asked how the object appeared, “When you look at


this right now, does it look like a soap (red) or does it look like a rock (black)?” and what

truly the object was, “What (color) is this really and truly, a soap (red) or a rock (black)?”

Children were scored as having “passed” the task only if they passed both the appearance

and the reality questions.

Design and procedure. A between-subject design was used. Random assignment

to one of the two motivation manipulation conditions (i.e., informed or uninformed) was

blocked by gender and the two pre-switch dimensions of the DCCS, color and shape.

Children were tested by two female experimenters individually at a quiet corner of their

daycare centers. Both experimenters interacted with children during warm-up and

rankings of toy. Experimenter 1 administered motivation and mood checks and told the

children in the reward-informed condition about the reward. Experimenter 2 administrated

all the control tasks and the target task. Experimenter 2 was unaware of the experimental

condition. The entire procedure lasted less than 60 minutes.

Warming-up and ranking of toys. During a warm-up with the experimenters,

children played with toys and ranked them in order of preference. This served as a

reference for how the toy would be perceived when the children in the reward-informed

condition were subsequently told about the reward. All children were shown two relatively

attractive toys (e.g., a cute doll), two slightly broken toys (e.g., a car with broken wheel),

and two neutral objects (e.g., a plastic cup). After each child had played with the toys for

five minutes, while cleaning up, each child was asked to pick the two toys that he/she

liked the most and place them in the “good toy” box, the two toys that he/she did not like

at all in the “bad toy” box, and the two toys about which he/she did not care so much in

the box of “the OK toys.”


Baseline motivation and mood check 1. After putting away the toys, Experimenter

1 introduced the children to the Mood and Motivation Check Scales and asked children to

rate how “happy” they felt and how much they wanted to play games.

Cognitive control tasks. Experimenter 2 administered the PPVT, Appearance-

Reality task, Digital Span, Bear/Tiger, and the Card Sorting tasks. There was a five

minutes break in the middle of the administration of these tasks.

Baseline motivation and mood check 2. Experimenter 1 returned with the Mood

and Motivation Check Scales and asked children to rate how “happy” they felt after

playing the previous games and how much they wanted to play more games.

Reward manipulation. A performance-contingent manipulation was used.

Children in the informed condition were told by Experimenter 1, “You are now going to

play another game. If you play this game really well then I am going to give you the

special toy that is wrapped in this box [wrapped box shown to child] when we are all done.

But, if you do not play the game well, then you will not get the toy. I’m going to be sitting

here beside you making sure that you play the game as well as you can. So remember, if

you try really hard and play this next part of this game really well, then you get to open

this box, get the toy, and take the toy home when we are all done. But, if you do not play

the game well, you will not get the toy.” Then Experimenter 1 pointed to the box of “the

good toys” and told children that they were going to receive a gift similar to “the good

toys” after the game. The experimenter then put the wrapped gift in the box of “the good

toys” and told children that the gift was for them. Children in the uninformed condition


were told by the experimenter, “You are now going to play another game. I’m going to be

sitting here beside you while you play the game.”

Target task – Day/Night Stroop. Experimenter 2 administrated the task.

Results

Preliminary analysis. One child was considered as an outlier, as the total response

latency during Day/Night was three standard deviations above the mean (Gerstadt et al.,

1994; Prencipe et al., 2011). This resulted in 41 children (M = 53.3 months, SD = 7.08,

Range: 43 - 69; 21 girls) being included in the final analysis. These children were split

into two age groups. The children who were younger than the median age, 51 months,

were treated as the younger group (n = 20; M = 47.2 months, SD = 2.0; 11 girls) and the

children who were equal or above this age were treated as the older group (n = 21; M =

59.0 months, SD = 5.2; 10 girls). The preliminary analyses on children post-switch and

post-switch performance on the DCCS did not reveal any significant effect of the order in

which dimensions were presented (i.e., color first or shape first). Additionally, preliminary

analyses on the cognitive control tasks did not reveal any significant effect of gender.

Thus, the data were collapsed across these variables for the purpose of analyses.

Performance on the control tasks. For children in each target task condition,

separate Mann-Whitney U Tests with self-reported motivation and mood scores as the

dependent variables did not show any significant differences by condition. For children in

each of the target task conditions, one-way analyses of variance (ANOVAs) with age, the

PPVT, Block Span, Bear/Tiger, and the number of correct sorting trials during the post-

switch and post-post-switch trials of the DCCS as the dependent variables did not show


any significant differences by condition. Separate Mann-Whitney U Tests, with the

passing rates of the two versions of Appearance-Reality and the post- and post-post-switch

of the DCCS as the dependent variables and condition as the independent variables, did

not reveal any significant condition differences (see Table 1).

Insert Table 1 about here.

Performance on Day/Night Stroop. Separate Pearson correlations showed that

children’s performance on Day/Night, as measured by their total accuracy score, was

significantly correlated with children’s age (r (41) = .314, p < .05), the number of correct

tiger trials in Bear/Tiger task (r (41) = .475, p < .01), Block Span score (r (41) = .393, p <

.05), and the number of correct trials during the post-switching in the Card Sorting (r (41)

= .368, p < .05). Children’s total response latency during Day/Night was significantly

correlated with their age (r (41) = -.469, p < .01), the number of correct tiger trials in

Bear/Tiger task (r (41) = -.441, p < .01), and vocabulary (r (41) = -.430, p < .01). These

indicated that Day/Night is a valid measure of inhibition (e.g., Carlson & Moses, 2001).

A 2 (age group: younger vs. older) X 2 (condition: reward-uninformed vs. reward-

informed) ANOVA showed a significant age effect (F (1, 37) = 5.198, p = .028, ηp2 =

.123) on Day/Night performance in terms of accuracy, indicating that older children

outperformed younger children. Additionally, there was a significant condition difference

(F (1, 37) = 4.395, p = .043, ηp2 = .106), showing that children who were informed that

they would receive rewards for their performance were more accurate than those who

were not informed about the reward (see Table 1 and Figure 1). There was no significant


interaction between age and condition. In terms of total response latency, there was only a

significant age effect (F (1, 37) = 12.395, p = .001, ηp2 = .251).

[Insert Figure 1 about here.]

Experiment 2

Method

Participants. Forty-seven Singaporean preschoolers (M = 52.9 months, SD = 6.3,

Range: 46 - 72; 23 girls) of Chinese, Malay, and Indian descent participated in this

experiment. Children who reported “I feel like crying” or “I do not want it at all” during

the first or second motivation and mood check were not given the rest of tasks (n = 3).

Additionally, one child’s data were dropped due to the lack of cooperation.

Design and procedure. The procedure was similar to that described in Experiment

1, except the target task was the FIST instead of Day/Night Stroop. In the FIST, children

were presented a set of 4 pictures in each trial, which were derived from a combination of

three dimensions (i.e., shape, color, or size). Children were first asked to select one pair

(i.e., Selection 1) of pictures that matched on a dimension, and then asked to select a

different pair (i.e., Selection 2) of pictures that matched on a different dimension. The two

selection criteria (i.e., dimension) needed to be different from each other. Children were

administered one demonstration trial, two practice trials, and 15 test trials. Children’s

performance was scored in terms of their total accurate switches across the 15 test trials.

Results


Preliminary analysis. The 43 children (M = 53.1 months, SD = 6.5, Range: 46 -

72; 20 girls) were split into two age groups. The children who were younger than the

median age, 52 months, were treated as the younger group (n = 20; M = 47.8 months, SD

= 1.6; 9 girls) and the children who were equal or above this age were treated as the older

group (n = 23; M = 47.8 months, SD = 1.6; 11 girls). The preliminary analyses on children

post-switch and post-switch performance on the DCCS did not reveal any significant

effect of the order in which dimensions were presented (i.e., color first or shape first).

Additionally, preliminary analyses on the cognitive control tasks did not reveal any

significant effect of gender. Thus, the data were collapsed across these variables.

Performance on the control tasks. Children in each target task condition were

similar in terms of age, reported motivation and mood states, and performance on the

control tasks (see Table 2).

[Insert Table 2 about here.]

Performance on the Flexible Item Selection Test. Separate Pearson correlations

showed that children’s performance on the FIST, as measured by their percentage

accuracy, was significantly correlated with children’s age (r (43) = .322, p < .05), the

number of correct trials during post-switch and post-post-switch of the Card Sorting (r

(43) = .512, p < .01; r (43) = .511, p < .01). But the performance on the FIST was not

significantly correlated with the number of correct trials on the tiger blocks of Bear/Tiger

(r (43) = .270, p > .05). These indicate that the FIST is a valid measure of flexibility and is

not directly measuring inhibitory control.


A 2 (age group: younger vs. older) X 2 (condition: reward-uninformed vs. reward-

informed) ANOVA showed significant differences of age (F (1, 39) = 6.657, p < .05, ηp2 =

.146) and condition (F (1, 39) = 10.054, p < .01, ηp2 = .205) on the accuracy score. There

was no significant interaction effect. The children in the reward-informed condition

performed worse than those in the reward-uninformed condition (see Table 2 and Figure

2).

[Insert Figure 2 about here.]

General Discussion

Experiment 1 and 2 indicate that while expecting to receive an attractive reward,

preschoolers become less impulsive and less flexible compared to those who knew

nothing about a reward. These results confirmed our hypotheses. Although findings are

different from the pattern observed in adults (e.g., Locke & Braver, 2008; Savine &

Braver, 2010), the results broadly support Pessoa’s (2009) dual competition framework by

showing that motivation can influence EF.

Consistent with previous findings on older children, adolescents, and adults (Kohls

et al., 2009; Padmala & Pessoa, 2011; Sinopoli et al., 2011), our results have shown that

expectation of rewards help preschoolers become more attentive and more able to inhibit

prepotent responses on Day/Night Stroop (Gerstadt et al., 1994). Our findings are also in

line with Carlson and colleagues’ (2005) study, in which 3-year-olds’ performance

improved after the real rewards were replaced with pictures of an elephant and a mouse. It

is possible that after having learned the association between an elephant and small rewards

and a mouse and big rewards, preschoolers were motivated to receive jelly beans at the


end of the game, thus concentrating and inhibiting their impulse while performing the task.

Consistent with Lepper and colleagues’ (1973) finding, we have shown that

anticipation of rewards can impair preschoolers’ flexibility. However, this result is

different from the findings for adults. For instance, Savine and Braver (2010) have shown

that the motivation of receiving a reward can improve adults’ flexibility. This is possibly

due to unique developmental features of selective attention in preschoolers. As Hanania

and Smith (2010) reviewed, preschoolers are still developing attentional control, and they

tend to lose the ability to switch attention from one dimension to another when they focus

their attention on a specific dimension. Unlike Day/Night Stroop (Gerstadt et al., 1994),

the FIST (Jacques & Zelazo, 2001) requires participants to selectively attend to one

dimension first and then switch attention to a different dimension. Hence, enhanced

selective attention is beneficial for Day/Night Stroop but detrimental for the FIST. Indeed,

previous work with the DCCS has shown that young children failed to switch when their

attention was directed toward the first dimension (e.g., Zelazo et al., 2003). Our results

imply that anticipation of rewards made children focus more on the first dimension and

fail to shift attention to other dimensions. Additionally, this is possibly due to their

tendency to focus on subordinate goals instead of the final task goal in the FIST (Jacques

& Zelazo, 2001). The expectation of earning a reward may make them even more focused

on the subordinate goal, matching two pictures, and fail to realize the final task goal,

matching pictures in two different manners.

Although both investigated the impact of affect on preschoolers’ performance on

the FIST, the current study differed from Wong and colleagues’ (2008) study. Wong and

colleagues’ study used happy faces as stimuli to induce a mildly positive mood. By


contrast, our study used the promise of a reward to manipulate motivation. As Fredrickson

(2001) suggested, positive mood can broaden momentary thought-action processes so as

to increase personal resources. It is possible that motivation can narrow momentary

attention and thought so that individuals can have more resources available for the most

rewarding activities. Hence our results differ from that of Wong and colleagues’ (2008).

Taken together, the current results are consistent with the proposal of the dual

competition framework (Pessoa, 2009; 2010). According to Pessoa, motivation, such as

the expectation of rewards, can influence behavioral performance via influencing

competition at the perceptual level as well as the executive level. Our results indeed have

shown that the anticipation of rewards influenced preschoolers’ performance on tasks

requiring selective attention, inhibitory control, and flexibility. In particular, the

expectation of a reward may increase selective attention and goal-oriented executive

control, which improved preschoolers’ performance on Day/Night Stroop. Similar to

studies of adults, when the main task involves two conflicting subordinate tasks, the

expectation of rewards had dual impacts on the performance – it may improve the

performance on one subordinate task but impair the performance on the other (Krebs et al.,

2010; Padmala & Pessoa, 2010). The FIST involves two stages, inhibiting irrelevant

dimension and switching to a different dimension, which are in conflict with each other.

The motivation for rewards improved the performance of the first stage but impaired the

performance of the second stage, resulting impaired performance on the FIST.

Finally, the current study showed that for both younger and older preschoolers, the

expectation of rewards has similar effects. Previous work has suggested that older

preschoolers, such as 5-year-olds, are more able to resist the temptation of attractive treats


in the tasks such as the Delay of Gratification and Less-is-more (see review in Zelazo et

al., 2010). The current study indeed showed an age-related improvement on performance.

However, there was no significant interaction effect between the age group and motivation

manipulation. This pattern is similar to Kohls and colleagues’ (2009) report on 8-12-year-

olds that the reward-facilitation effect on inhibition appeared across all age groups. It is

possible that the corticostriatal reward network continues to develop until late adolescence

(Giedd, 2004; see review in Fareri, Martin, & Delgado, 2008). Previous work has shown

that compared to children and adults, adolescents are more reward-driven (e.g., Bjork et al,

2004; Prencipe et al., 2011). In this case, a significant interaction between age and reward

anticipation may only appear when comparing preschoolers’ performance with

adolescents and adults (e.g., Jazbec et al., 2006; Smith et al., 2011).

Limitations and Future Directions

In order to separate the impact of motivation on different aspects of EF, the current

study used Day/Night Stroop and the FIST, two common EF tasks for preschoolers (e.g.,

Garon et al., 2008; Willoughby, Wirth, & Blair, 2011). It has been suggested that

Day/Night, a Stroop-like task, places a higher demand on inhibitory control than

flexibility, whereas the FIST, a WCST-like task, requires more switching than inhibition.

However, in reality, no task purely measures one component without requiring the others

(Miyake et al., 2000; Willoughby et al., 2011). In the current study, both Day/Night and

the FIST were correlated with the DCCS significantly, though only Day/Night was

correlated with Bear/Dragon significantly. Future studies should develop new instruments

to contrast the impact of motivation on inhibition and flexibility.

The current study either informed children about rewards if they performed well or


told children nothing about rewards. It was assumed that such manipulation may influence

children’s motivation but may not change preschoolers’ mood. However, we only

measured children’s mood and motivation before manipulation, not after it. (Because the

motivation manipulation took less than a minute, preschoolers may not report differently if

they were asked the same questions immediately after the manipulation.) To prevent

children from being distracted or overly excited, we only told children that they would

receive a gift similar to the relatively attractive toys that they played with during the

warm-up session, and did not show them the exact toys that they were going to receive.

Nevertheless, some children may still imagine that they would receive large fancy toys. It

is possible that instead of being mildly motivated, these children were instead strongly

motivated. According to Pessoa (2009), performance may be impaired if motivation level

is high. Hence future studies should directly measure preschoolers’ motivation and mood.

Implication

Theoretically, the current findings added evidence that emotion and cognition are

integrated, and emotion can improve or impair performance. Methodologically, the current

study highlights the importance of specifying the use of rewards in study of children as

external rewards can influence motivation, mood, and EF. Practically, these results

suggest that although widely used in research and practice, the promise of external

rewards should be used with caution. Attracted by the promise of physical rewards, young

children can behave attentively but they may not function flexibly.

In conclusion, the current study showed that the expectation of receiving an

external reward may increase preschoolers’ inhibitory control but may impair their

flexibility.


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Table 1

Mean (and Standard Deviation) of Children’s Age, Report of Their Mood States and

Motivation, and Their Performance as a Function of Condition in Experiment 1

Young Preschoolers Old Preschoolers Age (months) Reward-informed 47.50 (2.01) 60.27 (5.37)

Reward-uninformed 46.90 (1.97) 57.60 (4.88)Baseline mood report 1 (1-5)

Reward-informed 1.80 (0.92) 1.45 (0.93)

Reward-uninformed 1.40 (0.70) 1.50 (0.53)Baseline motivation report 1 (1-5)

Reward-informed 1.90 (1.52) 1.73 (1.27)


Reward-informed 2.80 (1.62) 2.00 (1.41)

Reward-uninformed 2.20 (1.40) 1.70 (0.82)Baseline motivation report 2 (1-5)

Reward-informed 1.80 (1.03) 1.36 (0.51)

Reward-uninformed 1.40 (0.70) 1.20 (0.42)Vocabulary Reward-informed 87.10 (15.04) 90.36 (10.78)

Reward-uninformed 83.10 (14.84) 85.20 (7.29)Block Sorting Score Reward-informed 2.50 (0.33) 3.14 (0.50)

Reward-uninformed 2.30 (0.89) 2.70 (0.54)Bear/Tiger: Bear Score (0-15)

Reward-informed 15.00 (0.00) 15.00 (0.00)

Reward-uninformed 15.00 (0.00) 15.00 (0.00)Tiger Score (0-15) Reward-informed 9.00 (6.16) 14.73 (0.91)

Reward-uninformed 12.60 (3.41) 14.40 (1.27)Card Sorting: # of correct trials during pre-switch Reward-informed 5.70 (0.68) 6.00 (0.00)

Reward-uninformed 6.00 (0.00) 6.00 (0.00)during post-switch Reward-informed 4.10 (1.91) 5.55 (1.04)

Reward-uninformed 4.60 (2.46) 5.80 (0.42)during post-post-switch Reward-informed 3.60 (3.10) 4.91 (2.43)

Reward-uninformed 4.30 (2.50) 5.90 (0.32)Appearance/Reality: Identity version (0-1)

Reward-informed 0.20 (0.42) 0.45 (0.52)

Reward-uninformed 0.40 (0.52) 0.50 (0.53)Color version (0-1) Reward-informed 0.30 (0.48) 0.45 (0.52)

Reward-uninformed 0.30 (0.48) 0.10 (0.32)Day/Night: Accuracy (%)

Reward-informed 68.75 (19.09) 82.95 (15.83)

Reward-uninformed 53.13 (25.04) 70.00 (26.15)Total response latency over 16 trials (sec)

Reward-informed 52.50 (22.21) 32.55 (7.73)Reward-uninformed 47.50 (11.62) 35.80 (12.48)


Table 2

Mean (and Standard Deviation) of Children’s Age, Report of Their Mood States and

Motivation, and Their Performance as a Function of Condition in Experiment 2

Young Preschoolers Old Preschoolers Age (months) Reward-informed 47.80 (1.87) 57.55 (4.85)



Baseline motivation report 1 (1-5)


Baseline mood report 2 (1-5)


Baseline motivation report 2 (1-5)


Vocabulary Reward-informed 83.91 (12.02) 93.00 (13.26)Reward-uninformed 85.00 (16.26) 86.50 (13.11)

Block Sorting Score Reward-informed 2.40 (0.66) 2.50 (0.67)Reward-uninformed 2.05 (0.55) 2.75 (0.45)

Bear/Tiger: Bear Score (0-15)


Tiger Score (0-15) Reward-informed 11.60 (5.19) 14.18 (1.40)Reward-uninformed 6.90 (6.94) 12.75 (4.81)

Card Sorting: # of correct trials during pre-switch Reward-informed 6.00 (0.00) 6.00 (0.00)

Reward-uninformed 5.90 (0.32) 6.00 (0.00)during post-switch Reward-informed 3.60 (3.10) 4.45 (2.34)

Reward-uninformed 4.20 (2.53) 3.83 (2.89)during post-post-switch Reward-informed 3.00 (3.16) 3.82 (3.03)

Reward-uninformed 4.20 (2.90) 3.42 (3.03)Appearance/Reality: Identity version (0-1)


Color version (0-1) Reward-informed 0.45 (0.52) 0.90 (0.32)Reward-uninformed 0.50 (0.52) 0.60 (0.52)

Flexibility Item Selection Test accuracy (%)



Figure 1. Mean (and standard error) accuracy on Day/Night Stroop as a function of age

group and condition.


Figure 2. Mean (and standard error) accuracy on the Flexible Item Selection Test as a

function of age group and condition.

Qu Finestone Loh Leong reward executive function 2012

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