the prevalence of aggression is 8 - 20% in three- to six - year - old children . biological and genetic factors , environmental learning , cognitive processing and personal stimuli or motives are some important causes of aggression . treatment of aggressive behavior at an early age is very important , as aggression in early years of life sets the ground for many problems in personal and interpersonal areas of the lives of aggressive children . for instance , it can lead to a weak self - concept , being rejected by peers , poor academic performance and can serve as a predictor of delinquency , depression , academic failure , substance abuse , more inappropriate and aggressive reaction to social issues , and choosing more aggressive solutions for solving problems later in life . on the other hand , childhood exposure to aggression may also influence life - long health through biological mechanisms . also , the economic costs imposed on the community due to youth aggression , bullying and violence are extremely high . yet , social - learning theorists contend that environmental factors are responsible for learning aggressive behaviors and continuing them . therefore , the children who learn aggressive behaviors are able to avoid such behaviors by means of reinforcement behavior therapy . reinforcement behavior therapy is defined as the  employment of reinforcement and extinction in order to increase the occurrence of desirable behaviors and decrease the incidence of behaviors that interfere with intended behavior  . ( 2011 ) compared the effectiveness of two methods , namely reinforcement and reward behavioral therapy and ellis s cognitive therapy , in the degree of aggression among 89 parentless children . the reinforcement and reward behavioral therapy method led to a significant reduction in aggression mean score before and after applying the procedure , whereas ellis s cognitive therapy technique did not show any significant impact on lowering aggression . the study of khazaie and colleagues did suggest the effectiveness of behavioral therapy in aggression ; however , it was carried out by a psychotherapist . in many countries , factors , such as insufficient number of professional psychotherapists or expenses of the procedure , therefore , training kindergarten and day - care centers teachers can be an appropriate alternative for offering proper interventions under the supervision of a therapist , so that a greater number of preschool children can benefit from such procedures . school environment interventions that impact on a range of health risk behaviors , including aggression , are likely to be one of the most efficient ways of modifying population - level risk . schools approaches to discipline , behavior management and aggression prevention vary widely and are rarely evidence - based , and that further resources and research are urgently needed to combat aggressive behaviors . although a large number of studies have so far been conducted on the effectiveness of complimentary therapies in reducing children s aggression , most of them have fundamental limitations . some such limitations include a greater focus on aggressive boys than girls , more emphasis on overt forms of aggression in comparison to more subtle forms like relational aggression . another treatment alternative is family therapy which , although very effective in children s behavioral problems , is quite costly and time - consuming . there is , therefore , a pressing need to determine which interventions are effective in addressing aggression in preschoolers , and if the intervention can apply effectively by kindergarten teachers to scale up such interventions across local and national school networks especially in developing countries . since children spend a great part of their active hours in kindergarten in close contact with their teachers , training the teachers can make a significant contribution to the elimination of aggressive behaviors . moreover , given the fact that each teacher is in charge of several children , providing teachers with trainings will result in saving the time and cost . in addition , the existing studies have addressed almost all forms of aggression except for impulsive anger . therefore , the present study has focused on all forms of aggression and aims to identify the effect of reinforcement behavior therapy by kindergarten teachers on all types of aggressive behavior among kindergarten and preschool children . it was a cluster randomized control trial research with a pretest / post - test design and control group . the study compared two groups of aggressive children , the intervention group receiving reinforcement behavior therapy and routine care by kindergarten teachers and the control group only receiving routine care . mohr is located in iran , in the southernmost part of fars province , 360 km away from shiraz . currently , there are 8 urban and 27 rural kindergartens and daycare centers in this city and about 1000 children attend these centers . the research population consisted of all three- to six - year - old kindergarten and preschool children in mohr . the inclusion criteria of the study were parental consent , children s age range of 3 - 6 years , and obtaining a minimum aggression score of 117.48 for girls and 125.77 for boys ( according to preschoolers aggression questionnaire constructed by shahram vahedi et al . on the other hand , the children or families with emotional crisis during the 2 months of intervention 14 out of the 35 existing kindergartens were selected through cluster random sampling method , as recommended by a demographer . then , all the 14 kindergartens were randomly allocated into either the intervention ( n=7 ) or the control group ( n=7 ) through block randomization by the researcher s assistant . the preschool aggression scale was distributed among the teachers to complete it for all 3 - 6 year old children in 14 kindergartens . using a study entitled  prevalence of behavioral problems in 3 to 6 year old children in hamadan city  and based on effect size=0.95 , power of 0.8 , and =0.05 , a 54 subject sample size ( 27 subjects in each group ) was determined for the present study . considering the probable loss in the sample , more than 117.48 for girls were randomly selected by simple randomization procedure by a table of random numbers from the list of aggressive children and their parents were asked to complete the written informed consent forms . the teachers of the kindergartens ( no=14 ) in the intervention group received 4 educational sessions based on positive reinforcement behavior therapy , but the teachers of kindergartens in the control group did not receive any interventions during the research period . each teacher in the intervention and control groups had about 15 children in his / her class . during the study , consort flow diagram of study participants in this study , the data were collected using preschoolers aggression questionnaire . this questionnaire aimed to evaluate various types of aggression , including verbal aggression , physical aggression , relational aggression , and impulsive anger . the reliability and validity of preschool aggression scale was studied by shahram vahedi et al . ( 2007 ) in a research on evaluation of aggression in preschool children of urmia , iran . the cronbach s alpha was estimated to be 0.98 for the whole scale , 0.93 for verbal aggression , 0.92 for physical aggression , 0.94 for relational aggression , and 0.88 for impulsive anger . a factor analysis of this scale using principal component analysis with varimax rotation resulted in four elements of verbal aggression , physical aggression , relational aggression , and impulsive anger , which was indicative of the construct validity of the scale . therefore , this aggression measurement scale can be used as a valid and reliable instrument in educational and clinical settings . in this 43-item questionnaire , the first 14 questions are related to verbal aggression and the next 13 are about physical aggression ; also , there are 9 questions on relational aggression , and the last 7 items deal with impulsive anger . this questionnaire was filled out by the teacher using 5 options ( 0=never , 1=rarely , 2=once a month , 3=once a week , and 4=often ) . the scores of verbal aggression , physical aggression , relational aggression , and impulsive anger were between 0 and 56 , 0 and 52 , 0 and 36 , and 0 and 28 , respectively . the children whose aggression scores were two standard deviations above the mean ( 117.47 for girls and four training sessions , each lasting for two hours , were planned for the teachers in the intervention group who were ready to take part in the study by an interventionist who was unaware of the aim of the study and was professional in behavior therapy . in the first session , the teachers were given some information about mental , psychological , and physical characteristics of the preschool children , and gained an understanding of how to deal with them properly . in the second session , the teachers learned about aggression in children , its types , causes , importance of early treatment of aggressive children , and general treatment techniques and methods . the third session intended to make teachers familiar with behavioral therapy and its various techniques , with a focus on reinforcement behavior therapy . the fourth and final session was entitled  practical work on reinforcement and reward behavior therapy  , and aimed to demonstrate how this technique works in practice , how to write down the details , and how to prepare an anecdotal record . the teachers were also given a written and practical test on proper practice of the technique . then , the teachers were asked to practice what they had already learned during their four sessions of training for aggressive children in the intervention group for 8 weeks . they were also asked to complete anecdotal record for every aggressive event in children , so that the researcher could follow up any changes in the aggressive children as well as the way the teachers implemented the procedure . in these forms , the teachers were asked to describe their reactions towards the children s aggressive behaviors in details and free from any judgment . then , in his weekly visits to the kindergartens , the researcher would review these forms and discuss them together with teachers . afterwards , if necessary , the teacher s reactions were modified and the required instructions were given . the control group , however , received no interventions throughout the course of research . yet , the demographic information questionnaire and the preschoolers aggression questionnaire were filled out by the teachers . after this project was carried out for two months , the teachers were asked to complete the same preschoolers aggression questionnaire for the children in both intervention and control groups for the second time and the results were evaluated by the researcher . the outcome measures in this study included the children s scores in the preschoolers aggression . the study data were collected by kindergarten teachers before and after the eighth week of the intervention . the teachers completed a demographic information questionnaire and the preschoolers aggression questionnaire . in this study , the data were analyzed using statistical package for the social sciences ( version 15 , spss inc , chicago , il ) . to evaluate the homogeneity of the participants characteristics in the intervention and control groups , chi - square smirnov test , paired t test and student s t - test were used for statistical analysis , as well . besides , p<0.05 was considered as statistically significant . the study was conducted in accordance with the human subjects protection principles ( declaration of helsinki ) . ethics committee approval was obtained from the research ethics committee of shiraz university of medical sciences . a written informed consent was obtained from the teachers and family of children for participation in the study . it provided the subjects with some information about the study , such as the purpose , e procedure , possibility of sharing the study results after completion , and promised anonymity in the event of publication of the study results . in addition , the subjects were assured that participation / non - participation would not affect their received care . the participants were allowed to withdraw from the research at any stage of the process if they or their parents were unwilling to continue their cooperation . moreover , after completion of the study , a handbook was prepared and given to the teachers and parents of the control group children . mohr is located in iran , in the southernmost part of fars province , 360 km away from shiraz . currently , there are 8 urban and 27 rural kindergartens and daycare centers in this city and about 1000 children attend these centers . the research population consisted of all three- to six - year - old kindergarten and preschool children in mohr . the inclusion criteria of the study were parental consent , children s age range of 3 - 6 years , and obtaining a minimum aggression score of 117.48 for girls and 125.77 for boys ( according to preschoolers aggression questionnaire constructed by shahram vahedi et al . on the other hand , the children or families with emotional crisis during the 2 months of intervention 14 out of the 35 existing kindergartens were selected through cluster random sampling method , as recommended by a demographer . then , all the 14 kindergartens were randomly allocated into either the intervention ( n=7 ) or the control group ( n=7 ) through block randomization by the researcher s assistant . the preschool aggression scale was distributed among the teachers to complete it for all 3 - 6 year old children in 14 kindergartens . using a study entitled  prevalence of behavioral problems in 3 to 6 year old children in hamadan city  and based on effect size=0.95 , power of 0.8 , and =0.05 , a 54 subject sample size ( 27 subjects in each group ) was determined for the present study . considering the probable loss in the sample , more than 117.48 for girls were randomly selected by simple randomization procedure by a table of random numbers from the list of aggressive children and their parents were asked to complete the written informed consent forms . the teachers of the kindergartens ( no=14 ) in the intervention group received 4 educational sessions based on positive reinforcement behavior therapy , but the teachers of kindergartens in the control group did not receive any interventions during the research period . each teacher in the intervention and control groups had about 15 children in his / her class . during the study , this questionnaire aimed to evaluate various types of aggression , including verbal aggression , physical aggression , relational aggression , and impulsive anger . the reliability and validity of preschool aggression scale was studied by shahram vahedi et al . ( 2007 ) in a research on evaluation of aggression in preschool children of urmia , iran . the cronbach s alpha was estimated to be 0.98 for the whole scale , 0.93 for verbal aggression , 0.92 for physical aggression , 0.94 for relational aggression , and 0.88 for impulsive anger . a factor analysis of this scale using principal component analysis with varimax rotation resulted in four elements of verbal aggression , physical aggression , relational aggression , and impulsive anger , which was indicative of the construct validity of the scale . therefore , this aggression measurement scale can be used as a valid and reliable instrument in educational and clinical settings . in this 43-item questionnaire , the first 14 questions are related to verbal aggression and the next 13 are about physical aggression ; also , there are 9 questions on relational aggression , and the last 7 items deal with impulsive anger . this questionnaire was filled out by the teacher using 5 options ( 0=never , 1=rarely , 2=once a month , 3=once a week , and 4=often ) . the scores of verbal aggression , physical aggression , relational aggression , and impulsive anger were between 0 and 56 , 0 and 52 , 0 and 36 , and 0 and 28 , respectively . the children whose aggression scores were two standard deviations above the mean ( 117.47 for girls and 125.77 for boys ) were diagnosed as aggressive . four training sessions , each lasting for two hours , were planned for the teachers in the intervention group who were ready to take part in the study by an interventionist who was unaware of the aim of the study and was professional in behavior therapy . in the first session , the teachers were given some information about mental , psychological , and physical characteristics of the preschool children , and gained an understanding of how to deal with them properly . in the second session , the teachers learned about aggression in children , its types , causes , importance of early treatment of aggressive children , and general treatment techniques and methods . the third session intended to make teachers familiar with behavioral therapy and its various techniques , with a focus on reinforcement behavior therapy . the fourth and final session was entitled  practical work on reinforcement and reward behavior therapy  , and aimed to demonstrate how this technique works in practice , how to write down the details , and how to prepare an anecdotal record . the teachers were also given a written and practical test on proper practice of the technique . then , the teachers were asked to practice what they had already learned during their four sessions of training for aggressive children in the intervention group for 8 weeks . they were also asked to complete anecdotal record for every aggressive event in children , so that the researcher could follow up any changes in the aggressive children as well as the way the teachers implemented the procedure . in these forms , the teachers were asked to describe their reactions towards the children s aggressive behaviors in details and free from any judgment . then , in his weekly visits to the kindergartens , the researcher would review these forms and discuss them together with teachers . afterwards , if necessary , the teacher s reactions were modified and the required instructions were given . the control group , however , received no interventions throughout the course of research . yet , the demographic information questionnaire and the preschoolers aggression questionnaire were filled out by the teachers . after this project was carried out for two months , the teachers were asked to complete the same preschoolers aggression questionnaire for the children in both intervention and control groups for the second time and the results were evaluated by the researcher . the outcome measures in this study included the children s scores in the preschoolers aggression . the study data were collected by kindergarten teachers before and after the eighth week of the intervention . the teachers completed a demographic information questionnaire and the preschoolers aggression questionnaire . in this study , the data were analyzed using statistical package for the social sciences ( version 15 , spss inc , chicago , il ) . to evaluate the homogeneity of the participants characteristics in the intervention and control groups , chi - square , fisher exact test and student s t test were applied . smirnov test , paired t test and student s t - test were used for statistical analysis , as well . besides , p<0.05 was considered as statistically significant . the study was conducted in accordance with the human subjects protection principles ( declaration of helsinki ) . ethics committee approval was obtained from the research ethics committee of shiraz university of medical sciences . a written informed consent was obtained from the teachers and family of children for participation in the study . it provided the subjects with some information about the study , such as the purpose , e procedure , possibility of sharing the study results after completion , and promised anonymity in the event of publication of the study results . in addition , the subjects were assured that participation / non - participation would not affect their received care . the participants were allowed to withdraw from the research at any stage of the process if they or their parents were unwilling to continue their cooperation . moreover , after completion of the study , a handbook was prepared and given to the teachers and parents of the control group children . the two groups were compared in terms of the children s age , both parents age , both parents level of education , both parents occupation , and family income ; they were similar regarding all the features , except for father s age . the means ( sd ) of aggression score in boys and girls were compared and shown in table 2 . all of the teachers were female between 20 - 35 years old and most of them had a bs degree ( n=20 , 72% ) ; 28% of them had high school diploma level of education ( n=8 ) . comparison of the demographic characteristics in the control and intervention groups meansd scores of aggression among boys and girls in both groups moreover , no significant difference was found between the two groups regarding the total aggression score ( p=0.55 ) as well as the scores of the four subscales prior to the intervention ( table 4 ) the mean score of aggression after the intervention showed a statistically significant difference between the two groups in this regard ( p=0.01 ) ( table 3 ) . moreover , a statistically significant change was observed in the intervention group s mean score of aggression after the intervention ( p<0.02 ) ; also , such a difference was found in the control group ( p<0.023 ) , but the results showed that the mean score of aggression in the control group was increased in the post - test compared to the pre - test . furthermore , the results revealed a decrease in the mean scores of verbal aggression , physical aggression , relational aggression , and impulsive anger in the intervention group after the intervention . yet , the difference between the intervention and control groups was statistically significant only for physical and verbal aggression subscales ( p=0.02 , p<0.01 ) ( table 4 ) . comparison of the frequency distribution of the participants in the intervention and control groups based on demographic characteristics x = chi - square ; f = fisher exact test comparison of the changes in the mean scores of various types of aggression in the preschoolers in the intervention and control groups before and after the intervention the present study aimed to investigate the effect of training kindergarten teachers regarding reinforcement behavior therapy on reducing different forms of aggression in preschool children . the study findings indicated that using reinforcement behavior therapy by kindergarten teachers resulted in a significant decrease in the total aggression , verbal and physical aggression , scores in the intervention group compared to the control group . it did alleviate the children s covert aggression , including relational aggression and impulsive anger , as well , but this change was not statistically significant . this finding supported the results of a study that indicated the effectiveness of reinforcement behavior therapy on abatement of childhood aggression . since children spend a long time at kindergartens in close contact with their teachers , it is possible to reform , or even eliminate , many behaviors that are possibly shaped at home . in this regard , a meta - analysis was performed by smeet et al , ( 2014 ) , on twenty - five studies to identify predictors of treatment response regarding cbt . furthermore , the treatment setting and duration did not seem to influence the treatment effect , which shows the need for development of more cost - effective and less - invasive interventions . there are limited studies that show the effect of behavior therapy by kindergarten teachers but to support the effectiveness of behavior therapy on the children s aggression , both verbal and physical , several studies have been conducted ; their results are all consistent with the present research . verbally and physically aggressive children can be detected more easily . since preventing this form of aggression parents are more sensitive and try to rectify the child s behavior and even seek help and advice from teachers . the children who display relational aggression are less responsive to psychological treatments because of the nature of relational aggression compared to other types and the deeper mechanisms involved in it . relationally , aggressive children were popular among their peers , causing short - term treatments not to have noticeable effects . the place these children gain among their peers because of their behavior makes them more resistant to medium - term psychological treatments . the results of the present study demonstrated a decrease in impulsive anger after the intervention ; however , this reduction was not statistically significant . this can be due to the fact that impulsive anger is a covert form of aggression and , consequently , it is sometimes not considered as aggression at all . ( 2012 ) showed that group therapy using parent - child relationship also did not have any significant effects on covert aggression . utilizing a primary , secondary and tertiary intervention model from the public health perspective can help the organization to address violence in each of these three domains . in the absence of school nurses in kindergartens , the teachers are the best choice for working with aggressive children . in this regard , the psychiatric mental health nurses in their community based approach can arrange educational programs for teachers to facilitate and improve their ability in providing psychiatric interventions such as reinforcement behavior therapy . short duration of treatment , small sample size , all female teachers , potential contamination across schools and the fact that evaluation of children s aggression at home is not possible were some major limitations of the present study . filling out the questionnaire by teachers can affect the result . in conclusion , the results of this research emphasized the effectiveness of reinforcement behavior therapy in reducing physical and verbal aggression in preschool children . nevertheless , it was shown that this technique was not sufficient to alleviate relational aggression and impulsive anger . this reminds us of the necessity for continuation of the treatment or designing another type of intervention which is more appropriate for these types of behavioral problems in children . in this study , therefore , using other psychological interventions in aggressive children is suggested to be used in future studies . studying the effect of positive reinforcement therapy on aggression and its sub - scales for more than 8 weeks is also recommended . moreover , qualitative studies are recommended to be performed on aggression in preschoolers in future . to improve evidence - based nursing , further studies on the impact of this intervention
background : aggression is a kind of behavior that causes damage or harm to others . the prevalence of aggression is 820% in 36 years old children . the present study aimed to assess the effect of training kindergarten teachers regarding reinforcement behavior therapy on preschoolers aggression.methods:in this cluster randomized control trial , 14 out of 35 kindergarten and preschool centers of mohr city , iran , were chosen using random cluster sampling and then randomly assigned to an intervention and a control group . 
 all 370 kindergarten and preschool children in 14 kindergarten were assessed by preschoolers aggression questionnaire and 60 children who obtained a minimum aggression score of 117.48 for girls and 125.77 for boys were randomly selected . 
 the teachers in the intervention group participated in 4 educational sessions on behavior therapy and then practiced this technique under the supervision of the researcher for two months . 
 preschoolers aggression questionnaire was computed in both intervention and control groups before and after a two - month period.results:the results demonstrated a significant statistical difference in the total aggression score ( p=0.01 ) , verbal ( p=0.02 ) and physical ( p=0.01 ) aggression subscales scores in the intervention group in comparison to the control group after the intervention . 
 but the scores of relational aggression ( p=0.09 ) and impulsive anger ( p=0.08 ) subscales were not statistically different in the intervention group compared to the controls.conclusion:this study highlighted the importance of teaching reinforcement behavior therapy by kindergarten teachers in decreasing verbal and physical aggression in preschoolers.trial registration number : irct2014042617436n1