Intelligence does not correlate with inhibitory ability at

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Procedia Social and Behavioral Sciences 12 (2011) 3–8

International Conference on Education and Educational Psychology (ICEEPSY 2010)

Intelligence does not correlate with inhibitory ability at every age Xiaoju Duan, Jiannong Shi* Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China

Abstract Accumulating evidence suggests that inhibitory ability is related to intelligence, while other studies don’t confirm this finding. This study explored the relationship of intelligence to inhibitory control in primary school children, aged 7- to 8-year-old, 9- to 10-year-old and 11- to 12-year-old. Raven’s advanced progressive matrices and Cattell’s Culture Fair Test were administered. The inhibitory ability was measured with a computerized Stroop Test. There was only significant correlation between intelligence and Stroop Test on 11- to 12-year-old children. These results suggested that the relationship between intelligence and inhibitory control was dependent on the participants’ age. © 2009 Published by Elsevier Ltd. Ltd. Selection and/or peer-review under responsibility of Dr. Zafer Bekirogullari of Y.B. Key words: Intelligence; Stroop Test; Inhibitory; Children; Development;

1. Introduction Inhibition plays an important role in everyday life as well as in higher cognitive activities. People need to respond appropriately by resisting inappropriate behaviors. Many researchers have argued that inhibitory ability is essential to intelligence. Dempster (1991) addressed that ‘‘intelligence cannot be understood without reference to inhibitory processes’’ after reviewing a number of researches relating measures of intelligence and inhibition. The measurements included various intelligence and inhibitory tests. The participants ranged from children to adults. Das (2002) also argued that the ability to resist distraction and ignore irrelevant information is important for the intelligent behavior. This ability could be understood as inhibitory ability. Previous studies have often utilized the Stroop paradigm in which irrelevant information must be suppressed or ignored and participants have to inhibit the predominant response (Dempster & Corkill, 1999; Johnson, Im-Bolter, & Pascual-Leone, 2003). There are normally three kinds of trials in the Stroop Color and Word Test. Participants are required to name the color of the words or other symbols. In the incongruent trials, participants need to resist the dominant tendency to read color words, instead of naming the color. Dependent variable is the naming time on incongruent trials minus naming time on neutral trials (Friedman et al., 2006; Homack & Riccio, 2004).

* Corresponding author. Tel.: +86-10-6485-5744; fax: +86-10-6487-2070. E-mail address: [email protected] 1877-0428 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Dr. Zafer Bekirogullari of Y.B. doi:10.1016/j.sbspro.2011.02.003

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Xiaoju Duan and Jiannong Shi / Procedia Social and Behavioral Sciences 12 (2011) 3–8

The correlation between intelligence and inhibitory was supported by many studies. Salthouse et al. (2003) found that inhibitory ability was strongly correlated with fluid intelligence in aging adults. Polderman et al. (2009) found the correlation between intelligence and inhibitory ability on 9-year-old, 12-year-old and 18-year-old children. Evidence also came from researches on the comparisons between different intelligence groups. Several researchers pointed out that the differences between intelligence groups stemmed not only from the ability to process relevant information but also from the ability to inhibit irrelevant information or inappropriate preponderant response (Johnson et al., 2003; Roberts & Pennington, 1996). For example, intellectually superior adults did better than average group at the Stroop Color Word Test (Parsons, 1984). Arffa (2007) investigated the role of intelligence level on the performance of several tests, in an average, above average, and gifted sample over 6- to 15-year-old children. It was found, that gifted group performed better at Stroop task than both above average and average groups. Our previous study also found that intellectually gifted children performed better than average children on a Go/NoGo response inhibitory task (Duan et al., 2009). There are also some studies which got different results. For example, Friedman et al. (2006) found that inhibiting was not related to Raven’s progressive matrices test, but related to the Wechsler adult intelligence scale intelligence quotient test on college students. The inconsistent findings from literature maybe come from the participants’ age. Participants were children in Polderman’s study, college students in Friedman’s study and elderly adults in Salthouse’s study. Developmental researches clearly showed that the inhibitory ability improved with development during childhood and adolescence (Van Mourik, Oosterlaan, & Sergeant, 2005). The relationship between intelligence and inhibitory ability could be influenced by the age of children. Polderman et al. (2009) found that the correlation between intelligence and inhibitory became stronger as children get older. But their data were collected from three different studies. Furthermore, the participants cover a wide age range from 9- to 18-year-old and they didn’t explore the relationship in younger children. The aim of the present study is to investigate the relationship between intelligence and inhibitory ability separately on 7- to 8-year-old children, 9- to 10-year-old children and 11- to 12-year-old children. We expected that the correlation of intelligence and inhibitory ability is greater in older children than it in younger children.

2. Method 2.1. Participants A total of 187 children participated in this study. They were selected randomly from one Chinese school. All participants had normal or corrected-to-normal vision, and were free from neurological or psychiatric disorders. Informed consent was obtained from participants’ teacher and parents. The participants were divided into 3 age groups: 7- to 8-year-old (N = 63; 23 girls; aged 7.88 ± 0.23), 9- to 10-year-old (N = 60; 29 girls; aged 9.86 ± 0.36), and 11- to 12-year-old (N = 64; 34 girls; aged 11.50 ± 0.63). 2.2. Material and procedure The tests to measure intelligence were Raven’s advanced progressive matrices and Cattell’s culture fair test. They were the most frequently used intelligence tests. There were 60 items in the Raven’s test and 40 items in the Cattell’s test. The instructions were in Chinese. There were no Chinese norms for both tests, so the numbers of the correct items were the test score. The Stroop Test was modified to be administered by computer and easy for young children. Participants were asked to judge the color of the words despite the meaning by pressing corresponding keys. There were two words, red and green in Chinese character, which were inked into two colors, red and green. This test had two kinds of trials. One


was congruent trials in which the color and the meaning of words were congruent. For example, “red” was inked red. The other kind of trials was incongruent trials in which the color and the meaning of words were incongruent. For example, “red” was inked green. The participants were told to judge the ink of the word as fast and accurately as possible. A block consisting of 36 stimuli (25% probability for each condition) was completed. The dependent variable was the reaction time of incongruent trials minus the reaction time of congruent trials. The Stroop Test was administered in small groups and every participant finished the tasks using computer individually. Instructions and practice trials were given at the beginning of test. Total testing time, including the instructions and practice, varied between 5 and 10 minutes. The stimulus presentation, data acquisition and calculation were collected using the E-prime software system. The intelligence test was administered in groups with approximately 30 children. The data analyses were carried out using SPSS 13.0.

3. RESULTS 3.1. Descriptive data The means (M) and standard deviations (SD) of the intelligence tests and Stroop Test for all the three age groups were provided in Table 1. Table 1. Descriptive Statistics 7- to 8-year-old 9- to 10-year-old 11-to 12-year-old M SD M SD M SD 1.Raven 34.42 9.93 42.95 6.72 40.91 7.69 2.Cattel 23.58 6.69 28.42 4.32 28.58 5.26 3.Stroop 117.81 396.68 24.70 177.65 32.44 120.07 4.RT-congruent 853.29 244.81 722.77 202.33 653.86 185.65 5.RT-incongruent 971.10 465.16 747.48 208.05 686.30 225.78 6.ACC-congruent .90 .17 .96 .06 .96 .06 7.ACC-incongruent .85 .20 .94 .07 .93 .07 3.2. Correlations The correlations between intelligence and Stroop Test for every age group were shown in Table 2. Table 2a. Correlations between intelligence and Stroop Test on 7- to 8-year-old 1 2 3 4 5 6 1.Raven 2.Cattel .515** 3.Stroop .039 -.002 4.RT-congruent -.015 -.070 -.005 5.RT-incongruent .025 -.038 .850** .522** 6.ACC-congruent .295* .383** -.058 .155 .032 7.ACC-incongruent .241 .341** -.046 .204 .068 .903**

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Table 2b. Correlations between intelligence and Stroop Test on 9- to 10-year-old 1

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1.Raven 2.Cattel .359** 3.Stroop -.107 -.130 4.RT-congruent -.054 .122 -.406** 5.RT-incongruent -.144 .008 .459** .626** 6.ACC-congruent .150 .231 .217 -.101 .088 7.ACC-incongruent .013 .108 .078 -.130 -.059 .429** Table 2c. Correlations between intelligence and Stroop Test on 11- to 12-year-old 1 2 3 4 5 6 1.Raven 2.Cattel .470** 3.Stroop -.268* -.405** 4.RT-congruent -.503** -.222 .047 5.RT-incongruent -.550** -.393** .570** .847** 6.ACC-congruent .020 .129 .109 .217 .237 7.ACC-incongruent .222 .161 .036 .046 .057 .241 Note: RT: reaction time; ACC: accuracy; ** p < .01; * p < .05 The correlations between the two intelligence tests, Raven’s advanced progressive matrices and Cattell’s culture fair test, were significant for all the three age groups. But the correlation between intelligence tests and Stroop was only significant on 11- to 12-year-old children. The RT and ACC were basic index for information processing speed. There was significant correlation between ACC and intelligence on the 7- to 8-year-old children. The higher the child’s intelligence the greater ACC she or he had. There were no significant correlations between RT, ACC of the two kinds of Stroop Test trials and the two intelligence tests on the 9- to 10-year-old children. On the 11- to 12-yearold children, we found significant negative correlation between intelligence tests and RT. The higher the child’s intelligence the faster she or he responded during the Stroop Test.

4. Discussion The present study used Stroop Test to investigate the relationship between intelligence and inhibitory ability, by focusing on three age groups, 7- to 8-year-old, 9- to 10-year-old and 11- to 12-year-old children. The main finding of the present study is that there was only significant correlation between intelligence and inhibitory ability on 11- to 12-year-old children. There was no relationship between intelligence and inhibitory on 7- to 10-year-old children. The nonexistent relation between intelligence and inhibition on 7- to 10-year-old children may initially seem surprising. However, these findings were similar to the previous study. Polderman et al. (2009) found that the correlation between intelligence and inhibitory became stronger as children grow up. The correlation coefficient was -0.16 for the 9-year-old, -0.24 for the 12-year-old and -0.35 for the 18-year-old respectively. The correlation coefficient was -0.13 between Cattell’s culture fair test and Stroop Test of the present 9- to 10-year-old sample. This number was close to Polderman et al.’s finding on the 9-year-old children. They got a quite big sample of around three hundred children. It was easy to get significant correlations from such big sample. Other evidence for strong relations between intelligence and inhibitory ability came from the comparison of different intelligence groups, clinical populations, adults or the elderly. The participants were quite different from the present normal children.


One possible explanation for the intelligence inhibitory correlation on 11- to 12-old children may lie in the genetic factors that were shared with intelligence and inhibitory ability. Stins et al. (2004) assessed the heritability of performance on the Stroop Color and Word Task, using 290 12-year-old twins. They found that nearly half of the variation in inhibitory performance was due to genetic variation and the genetic factors that influenced IQ also influenced inhibitory control. The correlations between ACC and intelligence on 7- to 8-year-old, RT and intelligence on 11- to 12-year-old children, were in line with the general idea that the information processing speed was closely related with intelligence (Sheppard & Vernon, 2008). There are some limitations in this study and implications for future studies that need to be addressed. Firstly, one limitation of the present research was the modified Stroop Test we used. Maybe it employed different cognitive ability to inhibit the action of key-pressing compared with reading as required in traditional Stroop tests. And there were only two kinds of trials in the present study with a lack of control conditions. As a result, our present findings can not apply to other inhibitory tests. Secondly, it is important to point out that the current data was based on a restricted sample of 7- to 12-year-old children. Therefore, the results may not be completely generalized to more cognitively diverse samples. It would be worthwhile to extend this work with different age groups in order to address developmental issues more adequately.

5. Conclusion Our present findings showed that the relationship between intelligence and inhibitory ability was changed according to the age of participants. Intelligence was correlated with inhibitory ability on 11- to 12-year-old children but not on 7- to 10-year-old children. Improved understanding of the relationship between intelligence and inhibitory ability will shed light on children’s school activities, intelligence development and other related cognitive abilities. Acknowlegement This work was supported by The work was supported by Natural Science Foundation of China (Grant No. 30670716) and Youth Science Foundation of Institute of Psychology, Chinese Academy of Sciences (No. YOCX392S01).

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