Is it useful for toddlers to learn beadwork? Why can't we use it in elementary school?

Survey on the bead counting education has the function of developing children's knowledge

Bead counting is one of the major inventions of China's ancient times. 1972 by Chinese-American physicist Dr. Li Zhengdao acclaimed: "Our Chinese ancestors, a long time ago, created the best computer, which is still in use today, the abacus." The invention of the abacus has made great contributions to the development of our culture, economy, science and technology. The design test data in the early stage of our country's development of the atomic bomb was also typed out with an abacus. With the rapid development and popularization of computers, the abacus is not comparable to computers in terms of calculation functions. In this case, elementary school have long ceased to set up the abacus class; accountants to obtain the qualification certificate, learned the computer no longer test abacus, financial institutions also stopped opening the abacus course, abacus education gradually into the doldrums. But on the other hand, more than 20 years after the practical exploration and development of the "bead heart calculation" (or brain bead calculation), so that the bead calculation by the development of computational tools into educational tools, the results are notable. The difference between bead computing education and traditional bead computing education is that: bead computing education, mainly teaching students to master bead computing technology; and bead computing education, focusing on the development of children's and teenagers' brain power, in addition to using bead computing technology to teach mathematics, with special emphasis on the use of both hands to dial beads and a certain amount of classroom bead computing, mental arithmetic training, arithmetic from shallow to deep, from simple to complex, prompting the development of the left and right brain cells to get as much as possible in order to The children are also able to use the abacus to add, subtract, multiply and divide multi-digit numbers and various kinds of addition, subtraction, multiplication and division mixed arithmetic problems, and can quickly calculate the results.

The education of children and teenagers in bead calculations, the relevant departments have some different opinions. In the new situation, the new situation, how to develop the bead calculation education, how to carry out the work of the Association of the bead calculation, faced with difficult problems. In order to make the work of the Association, can be better adapted to the actual situation, the Chinese Association of the beads on the beads of education to carry out a systematic investigation and research work.

First of all, we listened to the opinions of the comrades in the education system who had doubts about the education of bead calculation. Have invited three comrades to seek advice, their views are summarized in five points. First, the current need to reduce the burden on students, learning bead calculations, will increase the burden of learning students. Second, children and teenagers is the rapid development of the brain period, the need for multi-faceted stimulation, learning bead counting, every day mechanical training, is not conducive to the overall development of children. Third, in the age of information technology, the work needs to calculate the data to be accurate, can not rely on the mental arithmetic, or rely on the computer, do not need to spend a lot of time to train the child's ability to do quick calculations. Having the ability to do quick calculations is also useless in real life. Fourth, they also noticed that the children's academic performance has a certain positive correlation with the mental arithmetic education, but it remains to be seen whether there is any momentum. Fifth, the bead calculation education shows the role of developing the intellectual potential of children and teenagers, at present, only based on observation, statistics and reasoning judgment, can not be explained clearly by brain science, pedagogy. We feel that these opinions have some truth and deserve attention. Among the comrades who have just come into contact with this work within the Pearl Association system, there is also a certain degree of ****ming on the above issues. In the course of the survey, in the talks with students' parents, teachers and comrades of the grass-roots education departments, we discussed these issues with them and listened to their opinions.

Secondly, the organization of bead counting education results survey. China Pearl Association and the regional associations to carry out bead counting education, made a lot of pioneering work, and achieved great results. However, there is not enough summarization of the educational achievements, and many good experiences and experimental results have not been systematically summarized and lost in the grass-roots educational units and local bead associations. The CPCA issued a letter to all provincial bead associations, requesting them to investigate and report the results of bead calculation education and experiments. The local bead associations reported some teaching results and experimental materials one after another, and the reported materials showed

showed that the education of bead calculation was fruitful, which was gratifying.

Thirdly, the grassroots investigation. In Beijing, Shanghai, Zhejiang, Jilin, Heilongjiang, Sichuan and Shandong have been investigated, to each area are deep into a few kindergartens, elementary school for examination, listening to lectures, watching performances, understanding of learning achievements, verification of experimental data, and held by the teachers teaching bead calculations, parents and comrades of the education sector to participate in the symposium, listen to their views on bead calculations education and opinions.

Through the above systematic investigation and research, we further clarified the basic situation of bead calculation education, and deepened our understanding of the importance and necessity of bead calculation education, which made the focus of the work of the Association clearer. The importance and necessity of bead calculation education lies in the fact that it "has the obvious effect of developing the intellectual potential of children and teenagers". It is mainly manifested in the following aspects.

One, several can reflect the intellectual potential of the value of the obvious increase. Children and teenagers in the critical age (experts believe that the period of 4 to 9 years old) to learn 2 to 3 years of bead calculations, several major intellectual potential and non-intellectual potential to get a significant increase.

1. Calculation ability is extraordinary. The bead heart calculation technical assessment grade standard, addition and subtraction calculation, divided into 10 levels; multiplication, division, each divided into 7 levels. Elementary school grades 1-3, five classes a week, with the bead calculator for math teaching and training, generally can reach the bead calculator technical grade standard three algorithms of the fifth level. Level 5 standards are: addition and subtraction, in 5 minutes to complete 10 questions, each question 15 lines *** count 50 digital, including 4-digit 5 lines, 3-digit 10 lines. 10 questions total 500 digital. Combine 30 seconds to count one question. Multiplication 10 questions, including: 3-digit by 3-digit and 4-digit by 2-digit 2 questions each, 3-digit by 2-digit 6

questions, in 2 minutes and a half. Divide 10 problems, including 3 problems on dividing 5-digit numbers by 2-digit numbers, 3 problems on dividing 4-digit numbers by 3-digit numbers, and 4 problems on dividing 4-digit numbers by 2-digit numbers, in 2 1/2 minutes. Multiplication and division averages 15 seconds for one problem. Three types of arithmetic ***30 questions to be completed in 10 minutes, with 8 correct questions each to pass level 5.

The Able Level is faster. Can achieve "master" level is a minority. 2002, the first national bead counting technology competition won 60 people, of which 29 people aged 9 to 13. The first prize winner, with 15-20 rows of 120 digits for each addition and subtraction problem, completed 70 problems in 5 minutes and got 69 right, with a calculation time of only 4.29 seconds per problem; for multiplication, with 11-digit products, 152 problems were calculated in 5 minutes, and 151 problems were correct, with a calculation time of only 1.97 seconds per problem; and for division, with 10-digit divisors (e.g., dividing by 5 digits), 249 problems were calculated in 5 minutes, with all correct answers. In division, the division of 10-digit questions (e.g., divide by 5-digit number), 249 questions were calculated in 5 minutes, all correct, and the calculation time for each question was only 1.2 seconds, the calculation speed is so fast that the people who were present to watch were amazed.

2. The students who study bead calculations are not only good at math, but also good at other subjects. Nanjing Jiangning District Kirin Center Primary School teachers Zhang Meixiang, when the family into a comparison of the results of the bead counting teaching. Fourth-grade students in various subjects test results are shown in Table 1.

Jilin City, Jilin Province, Longtan District, Jiangmifeng Town Center Primary School for three consecutive school years of experimental comparisons, the results of the unified examination are shown in Table 2.

The achievement, not by increasing the intensity of bead counting teaching, but the bead counting education enhances the students' brain power, improve academic performance. According to the provisions of the national curriculum, elementary school 1-3 grade math professor job 9 hours, and Jiangmifeng Center Primary School experimental class, with the method of teaching bead calculations for math teaching, only 332 hours to complete the provisions of the content of the teaching than the syllabus provides for the saving of 117 hours, the provisions of the homework in the classroom can be done, not only to reduce the burden on the students, but also the use of the saved hours to increase the guidance of the students to think creatively! The content of the teaching is conducive to the overall development of students, and is conducive to the implementation of the policy of quality education.

3. Memory enhancement. Changshu City, Jiangsu Province, reported that the center of the elementary school memory test, the test four content: (1) 14 Arabic numerical disorder. (2) 10 letters of the alphabet without order. (3) 10 Chinese characters arranged in an unrelated order. (4) Memorize a children's song with a certain number of words. For the first 3 items, write the test on cardboard cards, show each item to the students for 10 seconds, and then ask them to write it out word for word in the original order in order to get it right. For item 4, students were given 3 minutes to memorize the words and then were asked to write the words without missing a beat. The sum of the digits and words that were memorized correctly was divided by the number of people who took the test to get the average test value per person. As a result of the test, the memorization ability of the students in the experimental class was significantly better than that of the students in the control class. Specific test values are shown in Table 3.

Yaoqiao Central Primary School, Dantu District, Zhenjiang City, Jiangsu Province, also made a memory test, the situation is shown in Table 4.

4. Improvement of thinking ability. Zhenjiang City, Jiangsu Province, Dantu District, Yaoqiao Central Primary School, based on educator Li Jiazeng edited "modern thinking and reform" and "creativity and creativity development and training" of the theory and rules of thinking ability test. The proportion of superior grades in each test item was much higher in the experimental class than in the control class.

The values of the test are shown in Table 5.

Table 1

Test Subjects Learning Beads and Minds Students (50 students learning Beads and Minds in grades 1-4) Control Students (50)

Mathematics 95 out of 80.5 points

Language 958 out of 85

English 95 out of 82

< p>Table 2

Grade level Teaching Language

Mean scores of students in the Unified Examination in the experimental class of teaching bead counting Mean scores of students in the class of experimental class of unteaching bead counting Mean scores of students in the class of experimental class of teaching bead counting Mean scores of students in the class of unteaching bead counting Mean scores of students in the class of experimental class of teaching bead counting Mean scores of students in the class of experimental class of teaching bead counting Mean scores of students in the class of experimental class of teaching bead counting Mean scores of students in the class of teaching bead counting Mean scores of students in the class of not teaching bead counting 95.46 points 92.34 points 3.12 points

Grade 2 98.05 points 90.22 points 7.83 points 94.73 points 89.63 points 5.10 points

Grade 3 94.28 points 86.58 points 7.7 points 92.33 points 87.00 points 5.33 points

Table 3

Test items Classes Arabic Numerals English Letters Chinese Characters Memorizing Children's Songs

Students in the experimental class 5.3 3.01 3.51 42.8

Students in the control class 3.77 2.41 2.61 31.0

(Note: The first three items are the average of three times of three years' tests, and memorizing children's songs is a single browsing value in the third grade.)

Table 4

Test Items Bead counting experimental class Control class

Superiority rate Pass rate Superiority rate Pass rate

Recognition of words 50% 96.7% 23.3% 90%

Recognition of images 26.7% 73.3% 6.6% 60%

Recognition of figures 26.7% 93.3% 26.7% 93.3%

Recognition of numbers 26.7% 93.3% 26.7% 93.3%

Recognition of children's songs 26.7% 93.3% 26.7 93.3%

(Note: Memorizing 80% correctly is considered excellent, and 50% correctly is considered a pass.)

Table 5

Test Data Classification Test Items Experimental Class (30) Control Class (30)

Excellent % Good % Medium % Poor % Excellent % Good % Medium % Poor % Excellent % Good % Medium % Poor %

Thinking Fluency 73.3% 23.3% 3.4% 30.0% 50.0% 20.0%

Thinking Sensitivity 60.0% 36.7% 10.0% 3.3% 13.3% 23.3% 36.7% 26.7%

Thinking Flexibility 16.7% 30.3% 26.7% 26.6% 3.3% 13.3% 33.4% 50.0%

Thinking Accuracy 6.7% 46.7% 30.0% 16.6% 16.7% 16.7% 46.7% 36.6%

Thinking variability 26.7% 23.3% 43.3% 6.7% 20.0% 36.7% 33.3% 10.0%

Forward versus backward thinking 43.3% 20.0% 26.7% 10.0% 3.3% 10.0% 56.7% 30.0%

Diffuse versus concentrated Thinking 30.0% 40.0% 30.0% 6.7% 26.7% 50.0% 16.6%

(Note:Bow from the article "Research and Practice of Bead Counting" of Yaoqiao Central Primary School, for the sake of comparison, human supplements are converted to relative supplements.)

5. Children who learn bead counting generally learn later. According to the study of bead counting primary school students after graduation tracking survey, suggests that learning has the stamina. Anhui province huangshan city qimen county yanjiang elementary school, learning bead calculations students into junior high school after the academic performance shows advantage. 1998 junior high school third grade 1st semester of the county examination results as table 6.

Table 6

distinction political language mathematics english physics chemistry total

The average scores of the students who have learned bead calculations (92-95 years of study of the 24 students) 77.1 65.4 76.8 87.8 91.0 85.3 483.5

The average score of students in the same grade who have not studied bead counting 53.5 53.6 52.6 70.3 69.9 61.4 361.2

At the eighth elementary school in Nehe Town, Qiqihar City, Heilongjiang Province, 5 of the 10 students who were among the first batch of students to study bead counting were admitted to university last year. The remaining five are currently studying in high school. Eighth primary school students, are the children of farmers, family education environment is not good, according to the provincial bead association reflects, once upon a time the school's students, did not go to college, this school is notorious for teaching bead counting. Of course, a rural elementary school can have five students in a year to go to college, but also with the university expansion.

6. Attention to self-control ability to enhance. General children and teenagers are not easy to concentrate, poor self-control. Through the training of bead calculations, gradually develop the ability of self-control of attention, attention and response to sensitive and flexible, which is important to improve learning efficiency, intellectual potential, there is an important significance.

Secondly, IQ is significantly improved. IQ test results, with the study of bead calculator children's intellectual potential development trend is consistent. Xinjiang has the first elementary school in Hezi City, IQ test. 1996, the first grade **** 6 classes, randomly selected 5 classes for the bead counting teaching experimental classes, 3 classes and 6 classes for the control class, 3 classes **** 181 students as experimental tracking and observation objects. By the end of 2000, 14 students were transferred and 167 students remained. IQ was measured using the Raven's Intelligence Scale and the Wechsler Intelligence Scale for Children, which are internationally recognized and have been revised domestically. The testers were all qualified by the National Psychological Test Training Course. Test results:In the pre-school test, the average IQ value of the experimental class was 101.18 and that of the control class was 103.94, with no significant difference. After three years of study test, the bead calculation class IQ value of 110.94, than the pre-school IQ value increased by 9.76; control class IQ value of 105.97, than the pre-school IQ value increased by 2.03, the bead calculation class IQ increase value is significantly higher than the control class.

The experimental class of bead counting was tested twice in Yibin Lujiajia Kindergarten in Sichuan Province. The first test was one year after the beginning of the experiment, and the second test was after the end of the second year of the experiment. 42 children started the bead counting experiment at the age of four years, and the grading statistics of the results of the two intelligence tests are shown in Table 7.

Table 7

Test results grading items Extremely excellent grade (>130) Excellent grade (120-129) Upper intermediate grade (110-119) Middle grade ( 90-109) Lower Intermediate (80-89) Below Marginal (<80 or less) Total

Theoretical Levels Distribution % (Statistical Law) 8.9 100

First Test Score Deposit % 100

Second Test Distribution % 100

The first test, which was carried out one year after the start of the experiment, was inexperienced in experimental teaching. It is still in the stage of teaching numbers by beads, IQ improvement is not obvious, IQ grade distribution, roughly the same as the theoretical distribution value. After two years of study, the teachers gradually accumulated experience, the teaching effect improved, and the children's IQ increased significantly. The proportion of children with IQ above the upper-middle grade accounted for 59.52%, which was 28.57 percentage points higher than the 30.95% in the first test, and 34.52 percentage points higher than the theoretical distribution value of 25.0% for the same grade. Moreover, the children below the lower-middle rank in the first test, the second test, the IQ have risen to above the middle. Mentally retarded children also have a significantly higher IQ after learning the bead math. Shanghai auxiliary reading (mentally retarded) school of mentally retarded children for bead counting education, 22 mentally retarded children for two and a half years (December 1997 to June 2000) of the teaching experiment, the middle of the transfer of 2 people, adhere to the experimental learning of 20, experimental teaching before and after the IQ test. The tests were conducted in accordance with uniform regulations: IQ tests were conducted using the "Kessler" scale for school-age children and pre-school intelligence; social adjustment tests were conducted using the "Simple Evaluation Method of Social Adjustment" in the Diagnosis of Children with Disabilities edited by Dr. Chen Yunying of the Central Textbook Institute; and mathematical tests were conducted using the United States' "Math Ability Situational Tests" and the "Math Calculation Ability Tests". ***Tested "group test, application problems, oral questions, number concepts and equations, estimation, calculation problems, charts, visualization, folding, mental arithmetic, etc. 10 items, 20 students tested 10 items of the total average score; pre-school test 25.9 points, post-school test 172.3 points, a significant increase in IQ. (This paragraph is quoted from page 66 of "Research on the development of the bead center curriculum" edited by Zhou Wei, Zhang Dehe).

Third, preliminary brain science tests have also certified the efficacy of BeadBuilder education in developing the intellectual potential of children and teenagers. Central Institute of Education, associate researcher Comrade Jiang Zhifeng on the bead brain mechanism of the preliminary experimental test research. He tested 43 third-grade students of Shilou Central Primary School in Fangshan District, Beijing, 21 of whom had been educated in bead counting and 22 of whom had not been educated in bead counting, and tested several cognitive functions: firstly, spatial memory test of numbers; secondly, attention scratching test (selective attention, breadth of attention, etc.); and thirdly, neuropsychological experiments including the level of memory for Chinese characters, the level of memory for images and the relative tendency of the brain's unilateralization. Third, neuropsychological experiments, including the level of memory for Chinese characters, the level of memory for images and the relative trend of unilateralization of the brain. The results of the tests were as follows: 1. In the unilateral brain test, there were significant differences in the reaction time and error rate of the learning beads and arithmetic group compared with the control group, the reaction time of the learning beads and arithmetic group was 422 milliseconds, and the error rate of the learning beads and arithmetic group was 0.13, and the error rate of the control group was 0.29, which was significantly better than the control group, and it indicated that the learning beads and arithmetic group had good development of the brain function; 2. The test of attention showed that there was a significant difference between the two groups, which included the level of memory for Chinese words, image memory and the relative trend of unilateralization of brain. The results show that there is a significant difference between the two groups, the average score of the bead calculation group is 45.30, and the average score of the control group is 31.92, which shows that the bead calculation group has an advantage in the degree of concentration and flexibility of choice.3. The number space test shows that there is a significant difference between the two groups in the inverse order of space, and the average number of the inverse order of digits of the bead calculation group is 6.80, and the average number of digits of the control group is 4.50, which shows that the bead calculation group has a better ability to extract information; the information extraction ability is better; the learning bead calculation group is better than the control group. The experiment also showed that there was a significant difference between the two groups in terms of total attention time in the number search task, with an average of 2112 milliseconds in the bead counting group and 3085 milliseconds in the control group, indicating that the bead counting group

group is more of an internalized mental activity, and its migratory effect is not in the periphery but in the central process. (This paragraph is quoted from Chiang Chi-Feng's paper < A preliminary study of the brain mechanism of the bead process〉).

Professor Li Xiuyan, director of the medical psychology teaching and research department at Weifang Medical College in Shandong Province, also conducted a preliminary test on the issue of bead calculations can develop the intellectual potential of children and teenagers, the number of test 30 people, 15 people learning bead calculations. The control group of 15 people. She found in the test:After bead counting training students, concentration, short-term memory is significantly higher than the control group of students. In Wechsler's children's math breadth measurement, the experimental group and the control group compared with a significant difference (P<0.05). Associative memory is an index reflecting the function of the right brain, and the score of associative memory of students in the experimental group was significantly higher than that of students in the control group (P<0.01), indicating that the bead calculations not only develop the left brain, but also have a strong role in developing the right brain. In the determination of EEG topography, it was found that there was no significant difference between the EEG power of the left and right brains in the quiet state in both experimental and control groups (P>0.05). However, there was a highly significant difference between the two during arithmetic (P<0.01), with the experimental group showing enhanced right brain EEG power during arithmetic.

Fourth, we are in the symposium, parents, teachers and grass-roots education department comrades of the speech on our understanding of the importance of the bead counting education is rich inspiration. China's bead computing education has a long history, but in the past to teach bead computing, only to teach bead computing technology, teaching until the actual use, to be practiced in the future work to improve. Learning bead calculations is different, after learning to see the results that can play a role in bringing a lot of convenience to work and life. Some parents have a small store, every day to review the bill of goods, spend effort, the child learns bead calculator has the ability to calculate quickly, look at the bill to know whether it is right. Some parents work in the industrial and commercial office, every day to open the receipt of seventy or eighty, before work to count the number of receipts, using a calculator, sometimes even a few times is not right, the child to see his mother counting the number of very difficult to help his mother to calculate the number of bills to look over the number of times will be right. Some grain warehouses in the peak season of grain purchases, pricing and settlement workload is too, I heard that the school has a "divine calculator", to the school to borrow two students to help, the work efficiency is very high, lifting the farmers in long queues to pay for the sale of grain troubles. Learning mental arithmetic, with the ability to calculate quickly, children have helped adults, the future work a lifetime of use. Learning bead counting students, due to strong memory ability, operation of the computer, input speed, error rate is much lower than those who have not learned bead counting, high work efficiency. Some teachers and comrades in the education sector believe that the bead counting education, not only does not increase the burden on students, but also to implement the quality of education and one of the most effective means of entry point.

The above series of facts show that the bead calculation education has fully demonstrated that "obviously has the role of developing the intellectual potential of children and teenagers", by some kindergartens, elementary school and students' parents welcome, only in Shanghai, there are more than 70,000 children and teenagers to learn the bead calculation. Weifang City, Weicheng District, Beiguan Primary School, as a result of the special teaching of mental arithmetic, reputation is increasing, the student population increased year by year, the students from the original 780 to 1198. The initial results achieved by the bead heart calculation education is very valuable and exciting.

Mental arithmetic has been around since ancient times. But the bead heart calculation is in the 1950s and 1960s began to rise in elementary school mathematics "three calculations combined" (bead counting, oral counting, penmanship) teaching method and bead counting this race training practice gradually discovered and developed. It also draws on international experience. According to the article, yichun city, jiangxi province, in 1958 began in elementary school trial implementation of the "three calculations combined" teaching method, tuhai city, chongming county, new river "five seven" three school elementary school trial implementation of the "three calculations combined" teaching method in 1969. Elementary school mathematics "three calculations combined" teaching method is strongly supported by the Ministry of Education, the rapid development of the country, the peak period of nearly 30 million primary school students to participate in the "three calculations combined" learning. 1978, the national implementation of the unified textbook of elementary school mathematics and later reduce the burden of learning measures, so that "three calculations combined" teaching is limited to the state of standstill. However, due to the significant development of the intellectual potential of children and adolescents, at the request of their parents and with the support of local associations and grass-roots education departments, the teaching of bead calculations in some schools has been maintained. Because of the fact that the bead calculation education is not allowed to enter the regular class, it has to be separated from the "three-calculation combination" teaching method and taught in the second classroom (the school can independently arrange the class time) or taught in the after-school time, and from then on, it forms the unique education of bead calculation. Bead calculation education is different from the "three-calculation" teaching." The "three-calculation combination" teaching is "bead math". The teaching of bead math focuses on developing the intellectual potential of children and teenagers, and there is a fundamental difference in teaching methods. At present, there are about 100,000 classes in the country, more than 3 million children and primary school students learning bead math. This development process shows that the "bead calculation" education is developed in decades of practice, is the national bead calculation and education sector **** with the efforts made, is a very remarkable achievement.

Some people mentioned earlier in this article have some doubts about the education of bead calculations. A large number of facts of practice and the results of preliminary scientific tests have basically answered the four doubts of "increasing the burden of learning", "useless to learn bead calculations in the age of information technology", "whether or not there is a future", "is not conducive to the child's all-round development", etc. The last doubt is that we have no idea of what to do with the bead calculations, but we are not sure if it is a good idea. The last doubt is that our understanding of the bead calculation education can develop the intellectual potential of children and teenagers is still preliminary, in the past the lack of organized and planned scientific experiments, basically stays in the stage of perceptual understanding of the bead calculation community at present can not be scientifically explained by brain science, psychology and pedagogy. Write this survey report, "focus on facts not theory". Because some theories are still ambiguous, pending in-depth scientific experiments to improve. The facts are the most persuasive, easy to get *** knowledge, and will cause a deeper exploration of the will and interest. Facts quoted in the report, as far as possible, using quantitative data. On the bead calculations can develop the intellectual potential of children and teenagers, is a very important issue, need the cooperation of all relevant departments, deep scientific exploration, to unravel the mystery, to promote the popularization of China's educational development and the revitalization of the Chinese nation, has a major far-reaching significance.

The current problems, mainly bead counting education effect in the community has produced considerable impact, and the market demand, followed by the emergence of a number of bead counting learning classes. Some of the bead counting teachers after standardized training, teaching quality is uneven, teaching effect is also a big difference, the need for the relevant departments to cooperate with each other to strengthen the standardization of management buried, so that the bead counting education can be scientific and healthy development.