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Inhibitory control is the ability to suppress competing, dominant, automatic, or prepotent cognitive processing at perceptual, intermediate, and output stages. Inhibitory control is a key cognitive function of typical and atypical child development. This study examined age-related trends of Stroop-like interference in 3 to 12-year-old children and young adults by administration of a computerized Stroop-like big–small task with reduced working memory demand. This task used a set of pictures displaying a big and small circle in black and included the same condition and the opposite condition. In the same condition, each participant was instructed to say “big” when viewing the big circle and to say “small” when viewing the small circle. In the opposite condition, each participant was instructed to say “small” when viewing the big circle and to say “big” when viewing the small circle. The opposite condition required participants to inhibit the prepotent response of saying the same, a familiar response to a perceptual stimulus. The results of this study showed that Stroop-like interference decreased markedly in children in terms of error rates and correct response time. There was no deterioration of performance occurring between the early trials and the late trials in the sessions of the day–night task. Moreover, pretest failure rate was relatively low in this study. The Stroop-like big–small task is a useful tool to assess the development of inhibitory control in young children in that the task is easy to understand and has small working memory demand.
Inhibitory control is the ability to suppress competing, dominant, automatic, or prepotent cognitive processing at perceptual, intermediate, and output stages (
Inhibitory control is often measured in young children by administering the Stroop-like day–night task (
Difficulty in the day–night paradigm is believed to arise because of response competition occurring within the response set during testing. Although it was expected that the stronger association between word pairs makes the task more inhibitory demanding, recent research has demonstrated that what causes prepotency of response is not the relation between the response-to-be activated and the response-to-be suppressed (
Working memory is also presumed to be an important factor related to the performance in the day–night paradigm. Working memory may be involved because resolving which of the conflicting responses must be suppressed entails holding the task rules in mind (“say ‘day’ for night card” and “say ‘night’ for day card”). In fact, some studies report deterioration in performance occurring between the first four trials and the last four trials in the sessions of the day–night task in young children (e.g.,
Working memory demands may also be related to learning the task rules. It might be true that the day–night task recruits working memory to a certain extent because learning the combination between words and pictures (“day” for a night picture of the moon and stars and “night” for a day picture of the sun) is not easy to understand for young children. Actually, previous studies with the day–night task had a great pretest failure rate, especially in children aged between 3 and 4 (e.g.,
This study was conducted to examine age-related trends of inhibitory control in various age groups by administration of a Stroop-like day–night variant with reduced working memory demand. For this study, 3 to 12-year-old children and young adults were administered a Stroop-like big–small task. The task used a set of pictures displaying a big or small circle in black and required participants to produce sized-based responses following instructions given by the experimenter. The size labels “big and small” were used because they are well understood even by very young children and because they are distinctive and opposite, both of which may facilitate learning and holding the task rules. The task has two conditions: the opposite condition, in which a participant says the opposite of what is shown with card pairs, and the same task condition, in which a participant simply names what the stimulus represents. Because the original study (
Participants were 113 typically developing people who were divided into six age groups: (a) 3–4 year, 20 children (10 boys, 10 girls; M age = 51.5 months, age range = 43–59); (b) 5–6 year, 14 children (7 boys, 7 girls; M age = 68.6 months, age range = 60–83); (c) 7–8 year, 20 children (11 boys, 9 girls; M age = 95.1 months, age range = 87–107); (d) 9–10 year, 19 children (9 boys, 10 girls; M age = 119.6 months, age range = 108–131); (e) 11–12 year, 17 children (9 boys, 8 girls; M age = 144.4 months, age range = 133–153); and (f) 23 young adults (9 men, 14 women; M age = 21.1 year, age range = 18–24). Children were recruited through local mainstream preschool and elementary school programs. Young adults were recruited from a university. All participants speak Japanese as a first language. Criteria for inclusion were the absence of bilingualism and absence of behavioral or educational problems, which would affect the study of inhibitory control.
The Stroop-like big–small task used a set of pictures displaying either a big (12 cm diameter) or a small (1 cm diameter) circle in black. The same set of pictures was used in the same and opposite conditions. SuperLab (Cedrus Corp., San Pedro, CA, USA) controlled the task, presenting stimuli and recording participants’ vocal responses (error and time).
Participants were tested individually in quiet rooms at their respective schools. At arrival, a participant was asked to be seated next to the experimenter at the table and approximately 50 cm in front of a monitor with a headset microphone. Subsequently, the experimenter explained that they were going to play a “game” in which they would see two pictures. The experimenter showed the participant the big and small circles at the same time on the screen and asked him or her to point to the big circle and the small circle in turn. All participants were able to do this. Then, each was administered the Stroop-like big–small task. In this task, the same condition was arranged to precede the opposite condition in an attempt to elicit robust interference.
Prior to the test phase, participants were trained on how to play each “game.” For the same condition, the experimenter said, “Here is a picture of big circle (show a big circle on the monitor). When this picture is shown, I want you to say ‘big’. And, here is a picture of small circle (show a small circle on the monitor). When this picture is shown, I want you to say ‘small’.” The participant did four practice trials (big–small–small–big). If the participant made any error, then the participant was corrected, reminded of the rules, and administered another four practice trials. The task did not commence until the participant was 100% correct for a set. For the opposite condition, the experimenter said, “We are going to play an opposite game. Here is a picture of big circle (show a big circle on the monitor). When this picture is shown, I want you to say ‘small’. And, here is a picture of small circle (show a small circle on the monitor). When this picture is shown, I want you to say ‘big’.” The opposite condition required participants to inhibit the prepotent response of saying the same, a familiar response to a perceptual stimulus. The practice trials were identical to the same condition.
During the test phase, the participant was asked to respond as quickly and accurately as possible to a series of 20 stimuli (10 big circles and 10 small circles) for each task condition. All stimuli were presented one at a time and randomly at the center of the white screen on the monitor. At the instant a participant’s voice key was input, each stimulus was replaced by a fixation cross until the participant was judged by the experimenter to be ready to proceed to the next trial, looking at the fixation cross. The interstimulus interval was not controlled by SuperLab, as it was in a card version of the task, because some younger children have difficulty engaging in the task continuously. No feedback reminding participants of the task rules was given during testing.
Numbers of errors and RT for correct responses were recorded. Trials were counted as incorrect when participants’ initial responses were errors, even if they self-corrected. The RT was measured as the interval in milliseconds between the presentation of a stimulus and the onset of the participant’s vocal response by the microphone. Analysis of RT was conducted only for the correct response. Mean and standard deviations of error rates and correct RT on the whole trials were calculated for each task condition. To examine changes of performance over the course of a session for each task condition, mean and standard deviations of error rates and correct RT were calculated for the first five trials and the last five trials, respectively.
The data were analyzed using analysis of variance (ANOVA). Specifically, two-way ANOVAs with the within-participant factor of condition (same and opposite) and between-participant factor of age group (3 to 4-year olds, 5 to 6-year olds, 7 to 8-year olds, 9 to 10-year olds, 11 to 12-year olds, and young adults) were conducted for error rates and correct RT. Also, three-way ANOVAs with the within-participant factors of condition (same and opposite) and serial position (first five trials and last five trials) and between-participant factor of age group (3 to 4-year olds, 5 to 6-year olds, 7 to 8-year olds, 9 to 10-year olds, 11 to 12-year olds, and young adults) were conducted for error rates and correct RT. Software was used for statistical analyses (SPSS 19.0 for Windows; SPSS Japan Inc., Tokyo, Japan). Unless otherwise noted, a 0.05 level of significance was adopted for all statistical analyses.
Informed consent was obtained from all adult participants and from a parent of each child participant before the assessment session. Our experimental protocol was administered in accordance with the guidelines of the Declaration of Helsinki and was approved by the institutional review board.
An additional 14 participants were tested. Data from 9 participants were not included in this study because they showed results more than 3 SD from the mean of each age group (i.e., outliers). One 3-year-old child was not able to pass a pretest for the saying-opposite condition. Another 3-year-old child was not able to complete the task because his voice was too small to record. Three school-age children were excluded because of experimental error in recording the data.
This study examined age-related trends of Stroop-like interference in 3 to 12-year-old children and young adults by administration of a computerized Stroop-like big–small task. In this study, the differences between the opposite and same conditions were compared among age groups for error rates and correct RT. It was hypothesized that working memory demand is reduced in the Stroop-like big–small task.
Results show that Stroop-like interference decreased markedly in children. The difference between conditions in error rates was significant for 3 to 4-year olds and 5 to 6-year olds but not for the older age groups although there were trends toward significance for some older age groups, which may be due to relatively small sample size. These results are consistent with the results obtained from previous studies using the day–night task and other variants of this task (
This study used a variant of the day–night task particularly addressing the concept of size, “big” and “small.” These sizes were concrete for participants in this study because they were perceptual features of the stimuli that were used, which seemed to facilitate sampling of young children, having them feel more comfortable by learning and holding the rules in mind. Actually, fewer children refused participation or were unable to pass the pretest, compared to those of the original study using the day–night task (
In conclusion, this study demonstrated that the difference between naming what stimuli represent and naming of the “opposite” of the stimuli was decreased significantly during young childhood in the Stroop-like big–small task that has smaller working memory demands than the original version of the day–night task. In other words, this study showed that inhibitory control develops rapidly in young children. The Stroop-like big–small task is a useful tool to investigate the development of inhibitory control in young children in that the task is easy to understand and has small working memory demand.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The authors thank all who participated in the study. This research was supported by the Japan Society for the Promotion of Science Research Fellowship for Young Scientists (to Yoshifumi Ikeda).