Developmental roots of distributive justice decisions between childhood and adolescence: cognitive development or socialization?

Distributive justice decisions are a fundamental aspect of social life. Which criteria (contribution, need, equality) do children and their parents use when deciding what they consider to be a fair distribution in situations where the criteria of contribution and need may conflict? And how can these decisions be explained? The present study examines three possible explanations for the development of distributive justice decisions between childhood and adolescence: (1) cognitive development, (2) value socialization by parents and (3) value socialization through different school environments. These questions were investigated longitudinally at two time points. German children participated the first time at age 10 (T1, n = 209) when they were in elementary school and a second time at age 12 (T2, n = 206) when they attended different tracks of secondary schools. Both children and their parents (n = 109 at T1; n = 143 at T2) took part in an experiment in which they allocated resources 18 times between two recipients who systematically differed in effort and need. At age 10, children gave less resources to the diligent child as compared to age 12. Further, they either allocated the resources only according to the need of the recipient or considered both need and effort in their allocation decisions (integration). Two years later, at age 12, the number of children who integrated both criteria increased, supporting the hypothesis that moral development is driven by cognitive growth. At both T1 and T2, parents either gave more to the recipient who had invested more effort or integrated need and effort. The distributive justice decisions of parents and their children did not align in most parent–child pairs. The type of secondary school only influenced decisions in scenarios where one recipient was very needy. In these cases, students from the least academically oriented schools disregarded the level of effort exerted by the recipient. The results suggest that cognitive processes constitute the main developmental roots of distributive justice decisions between childhood and adolescence.

The question of fairness preoccupies human beings throughout their lives. Interactions, wherever they take place, are constantly accompanied by the expectation that things should be fair. However, what constitutes fairness is often a matter of debate. In the case of distributive justice decisions, there are a number of principles that differ from one another in terms of which characteristic is central. Particular attention is paid to the principles of contribution, need, and equal distribution (Damon, 1990; Deutsch, 1975). The principle of contribution, sometimes also called the equity principle (Adams, 1965), demands that each person's share is in accordance with their contribution or input (e. g., merit, effort). The need principle ensures fairness by giving more to those who have less. According to the principle of equality, everybody should get the same share.

From a developmental point of view, it is interesting to ask (1) whether the decisions for a certain principle vary by age and (2) how these decisions can be explained. Various cross-sectional studies focused on the investigation of single criteria in children. They concluded, that, on the one hand, the preference for equal distribution decreases (Huppert et al., 2019; Schmidt et al., 2016) and, on the other hand, the tendency to favor recipients who have contributed more or are more needy increases (Cowell et al., 2019, 2025; Huppert et al., 2019; Rizzo and Killen, 2016; Schmidt et al., 2016) during childhood. Other research highlights the relevance of context (Wong and Nunes, 2003, 2014; Zhang, 2020) and provides evidence that, as children grow older, they increasingly take the allocation context into account (e.g., Kienbaum and Wilkening, 2009; Sigelman and Waitzman, 1991).

What these studies cannot answer is the question of how people of different ages, like children and their parents, allocate resources when faced with conflicting information—such as when a recipient is in need but has not contributed—and which mechanisms underlie these decisions. Longitudinal studies capable of elucidating why certain developmental trajectories occur are scarce.

The goal of the present research is to explore the developmental roots of distributive justice decisions with longitudinal data obtained between childhood and adolescence in situations where both contribution and need vary systematically. Three potential explanations for the development—cognitive development, value socialization by parents and/or value socialization through different school environments—were considered and will be explained in more detail in the following.

Cognitive development

The idea that the development of distributive justice decisions has its roots in cognitive processes goes back to the early work by Piaget (1954). He asked children between 3 and 11 years to decide whether and why a given distribution is fair. Based on these interviews, he described the developmental course of thinking about justice through qualitative changes: Until 7 or 8 years, children do not yet have a sense of justice, as they accept everything an authority figure says to be fair. Between 8 and 11 years, they strongly rely on equal distributions, whereas at about 11 or 12 years, extenuating circumstances, especially the notion of need, are taken into account.

William Damon (1990), building on Piaget's ideas, interviewed 4- to 10-year-old children and came to similar results, although with slightly different age ranges. He concluded that children until 4 years of age tend to favor themselves. At about 5 years, equality is the only principle that is acknowledged. Children aged 7 to 8 rely on equity, followed by the principle of need at about the age of 8. Afterwards, different principles are considered on the basis of the specific situational demands.

Both authors describe a developmental progression in which different distribution principles are favored depending on a child's age. Their models are based on the assumption that younger children prefer distribution principles that are cognitively less complex, whereas older children make use of more cognitively demanding ones. Equality can be considered the least cognitively demanding principle, since it does not require proportional thinking (Hook, 1978). Contribution follows, since, in Piaget's (1954) terms, it is an objective factor, as it is usually easy to observe in children's everyday life, for example in the form of work accomplished. Need, a subjective factor, is considered the more demanding principle, as it must be inferred (e.g., wearing less fancy clothes might mean that the family doesn't have much money).

In summary, according to the findings of Piaget (1954) and Damon (1990), by the end of childhood, children have mastered the three main principles of distributive justice decisions (contribution, equality and need) and are able to apply them with respect to a specific situation. Recent empirical evidence confirms these statements, with regard that children typically progress from preferring equality to preferring contribution or need during childhood (Cowell et al., 2019, 2025; Huppert et al., 2019; Rizzo and Killen, 2016; Schmidt et al., 2016). Moreover, research indicates that with increasing age, children show a growing tendency to consider the context of allocation decisions (e.g., Kienbaum and Wilkening, 2009; Sigelman and Waitzman, 1991).

What these authors do not tell us is how development continues beyond childhood, how people of different ages make decisions when principles such as contribution and need conflict, and by what mechanisms these choices can be explained. Studies with a longitudinal design, focusing on the transition from childhood to adolescence and asking participants to make distributive justice decisions for situations in which contribution and need are systematically varied, are scarce. Zhou et al. (2023, Exp. 2) asked Chinese children between 6 and 11 years of age to allocate medical resources between two recipients. One of them was needy and contributed less, whereas the other was not needy and contributed more. Only the oldest children (10–11 years) allocated more than half of the resources to the needy child who had contributed less, whereas the younger children all gave less than half. The authors conclude that, as children age, they gradually come to prioritizing need over contribution.

A systematic variation of different manifestations of effort and need was conducted in the framework of information integration theory (Anderson, 1996). This theory examines how people integrate multiple pieces of information into an overall judgment or decision. Anderson posits that information is integrated according to specific, mathematically describable rules, such as addition or multiplication. Many studies, for example on intuitive physics, show that children as young as 5 years are able to take two or even more stimulus dimensions into account in their judgments (e.g., Anderson and Cuneo, 1978; Wilkening, 1979, 1981; Wilkening and Huber, 2002). Concerning distributive justice decisions, Anderson and Butzin (1978) conducted experiments with children from 4 to 8 years of age. Their task was to allocate rewards between two story characters who differed in effort, need, or both. The results showed even some 4-year-olds could integrate information about effort and need, combining the two principles according to an adding rule. This ability increased linearly with age. In later cross-sectional studies conducted in Switzerland, Germany and Italy, children distributed resources primarily on the basis of the principle of need, whereas adolescents increasingly took both effort and need into account in their decisions, thus integrating the two principles (Kienbaum and Wilkening, 2009; Kienbaum, 2013; Kienbaum and Mairhofer, 2022).

On the basis of these results, we supposed for the present longitudinal study that an age-correlated increase in integration of effort and need between childhood and adolescence would be indicative for cognitive developmental processes behind the development of distributive justice decisions, since integrating two principles is cognitively more demanding than relying just on one. Expectations concerning context were not formulated, since all participants were investigated within the same context.

Value socialization: parents

Apart from cognitive processes, resource allocation decisions between two individuals who differ in both contribution and need may also be guided by underlying values, which are often shaped within the family context. Although parents likely socialize their children's values through processes such as modeling and guided learning (Grusec, 2023), empirical research on whether socialization processes contribute to the development of distributive justice decisions remains limited.

Early evidence for the impact of modelling comes from a study of 11-month-old infants who showed a head-orienting preference for unfair over fair distributors when their mother had previously turned her head toward the unfair distributor (Geraci et al., 2026). If the mother did not show any preference, the children's attention did not differ between the two distributors. These findings suggest that early mother-child interaction can shape children's preferences regarding distributors that are fair or not. The effectiveness of modelling was further illustrated by Blake et al. (2016). In this study, American and Indian children between 3 years and 8 years donated fewer candies compared to a baseline after they watched their parents make a stingy donation. Rottman et al. (2020) demonstrated that children aged 6 and 7 years changed their distribution principle from equal distribution to distribution based on merit—or vice versa—when an adult statement led them to believe that the alternative principle was better, thus providing evidence for the effectiveness of guided learning. These studies therefore demonstrate at least a short-term effect of parental or adult behavior on children.

Modelling as well as guided learning can be found in everyday interactions between parents and children. For example, when faced with a beggar, parents can comment that this is a person who needs help or that the person is to blame and should better work. The internalization of utterances like this should in turn influence children's distributive justice decisions when they, for example, have to decide whom to give more to: Someone who is needier or someone who has worked more. In the present study, we asked both the children and their parents to take part in the same experiment, in order to determine whether they would choose the same principles (effort, need, integration of both effort and need, equality) for their distributive justice decision or not. A match would indicate a possible transfer of parental values to their children. This match should be higher the longer the parent-child interaction lasts.

Value socialization: school environment

Another area of children's lives that has received comparatively little attention in connection with the socialization of distributive justice decisions is the school environment. A cross-sectional study from Germany (Kienbaum, 2013) examined the distributive justice decisions of students attending various secondary schools. In Germany, students are tracked to different types of secondary schools based on their performance at an early age, after the fourth grade of elementary school. One of these types leads children to an academic education (Gymnasium), while others are intended to lead to vocational training or nonacademic careers (Hauptschule and Realschule). In the federal state in which the study was conducted, the decision on the type of secondary school to be attended is based on teachers' recommendations, which are usually based on students' prior academic performance. The underlying idea is that children with the strongest cognitive abilities should attend Gymnasium and those with the weakest cognitive abilities should attend Hauptschule. The three-tiered system was designed to foster the early development of students' individual abilities and to prepare them for entry into the labor market in a manner that aligns with their aptitudes. However, the findings of the 2000 PISA study, at the latest, indicated that the tracking system exerts a segregating effect, as students' socio-economic status and social background are strongly associated with educational success or failure in German schools; in particular, students attending the Hauptschule are disproportionately more likely than those in other school types to be socially disadvantaged and/or to have a migration background (Davoli and Entorf, 2018). Baumert et al. (2006) described Gymnasium and Hauptschule as “socially and ecologically very different school environments” that “also represent differential learning and developmental milieus—both in terms of performance and personality development” (p. 98). Gymnasium education is characterized by high academic demands, requiring students to invest substantial effort to achieve success. In contrast, students attending Hauptschule may place less emphasis on effort for several reasons. Experiences in elementary school may have conveyed to them that their level of achievement was insufficient for admission to a higher-track school, despite exerting effort comparable to that of their peers. Furthermore, given the comparatively limited labor market opportunities associated with a Hauptschule qualification, these students may question the utility of investing effort altogether. Additionally, pervasive negative societal evaluations of Hauptschule (e.g., Völcker, 2016) may further reinforce maladaptive performance-related belief systems.

Kienbaum (2013) found that students who attended a Gymnasium were more likely to base their distributive justice decisions on the principle of effort than those who attended a Hauptschule. In contrast, Kienbaum and Mairhofer (2022) found no differences between students from different secondary schools in an Italian sample. In Italy, unlike Germany, there is no early school tracking. It could therefore be that early tracking into different types of secondary school based on performance is accompanied by a development of values that differs depending on the type of school: more achievement-oriented in the more academic schools compared to the less academic ones.

In order to test this assumption, we investigated children a first time at age 10, when they were still in elementary school, but knew already which secondary school they were designed to: Hauptschule or Werkrealschule (further called lower vocational track), Realschule (further called higher vocational track) and Gymnasium (further called academic track). Werkrealschule represents a type of lower vocational track school that was introduced in Southern Germany since Hauptschule increasingly lost prestige and student numbers declined. It did not constitute a fundamentally new school type but rather represented a reformulated extension of the traditional Hauptschule, since both institutions were based on the same curriculum, shared the same target group and vocational orientation (Kultusministerium Baden-Württemberg, n.d.). Two years later, at age 12, we investigated the students a second time. If the school environment does cultivate different values depending on the type of school, with academic track putting more emphasis on effort and merit than lower vocational track, the students' pattern of distributive justice decisions should differ accordingly.

The present study

The aim of the present study is to investigate if and how cognitive development, socialization in the home and/or in school can explain the development of distributive decisions in the transition from childhood to adolescence. To the best of our knowledge, this is the first study to investigate these three possible sources of development in a study with a longitudinal design. To this end, a group of students was examined twice, the first time at age 10 and the second time at age 12. This age range was chosen because, as described above, in Germany, after the fourth grade, when children are usually 10 years old, tracking into different secondary schools takes place. By examining the students once before and once two years after tracking, it is possible to test whether differences associated with the respective school type will occur. In addition, parents were asked to participate in the experiment at both measurement points. In sum, the following questions were examined:

Is there a development in the distributive justice decisions of students between the ages of 10 and 12 that suggests cognitive development progress? Cognitive development was expected to express itself in the increase of judgments that integrate effort and need.

Do children and their parents base their distribution justice decisions on the same criteria (effort, need, integration of effort and need, equality)? This match should occur at both ages 10 and 12. Based on the assumption that socialization is more effective the longer it takes place, the match at age 12 should be even higher than at age 10.

Can differences be identified in the distributive justice decisions of students between the ages of 10 and 12 that are associated with the type of secondary school they attend, with students from academic track schools basing their distributive justice decisions more often on the principle of effort than students from lower vocational schools?

Participants

Data collection took place in a midsize town in Southern Germany. We performed a power analysis with MorePower, a statistical program that allows to calculate power-related statistics for complex designs including both within- and between-subjects measures (Campbell and Thompson, 2012). The design of the present study consisted of three within-subject factors (time, effort, and need) and one between-subject factor (type of school). The sample size required for a mixed design with 2 × 3 × 3 × 3 factors, given a power of 0.99 with η 2 p = 0.06 and p < 0.05, was N ≥ 168. In order to account for potential dropouts due to the longitudinal design, we ran approximately 20% more participants than we needed.

The sample at T1 consisted of 209 children who all attended fourth grade in elementary school (104 girls, M age = 10.32 years, SD = 0.46 years; 105 boys, M age = 10.43 years, SD = 0.47 years). Two years later, at T2, 206 children (102 girls, M age = 12.27 years, SD = 0.44 years; 104 boys, M age = 12.39 years, SD = 0.46 years), participated again. They attended 52 different secondary schools. Among these, 36 children attended lower vocational track schools, 69 higher vocational track schools and 99 academic track schools. These proportions correspond to the breakdown by school type in the federal state in which the study was conducted (Statistisches Landesamt Baden-Württemberg, 2014). Two children attended other schools and were not included in the data analyses concerning school type.

Further, 85 mothers (M age = 41.58 years, SD = 4.43 years) and 24 fathers (M age = 45.52 years, SD = 5.68 years) participated at T1 and 103 mothers (M age = 45.10 years, SD = 4.87 years) and 40 fathers (M age = 48.40 years, SD = 4.87 years) at T2. The number of parents increased at T2 because they were offered an incentive of five euros. Fifty seven mothers and 12 fathers participated at both times. For 20 children at T1 and 32 children at T2, both parents took part in the study.

Among the participating mothers, at T1, 10 had children that were assigned to lower vocational track, 21 to higher vocational track and 54 to academic track schools. At T2, the corresponding numbers were 10, 32, and 61. Among the participating fathers, at T1, three had children that were assigned to lower vocational track, seven to higher vocational track and 14 to academic track schools. At T2, the corresponding numbers were 2, 11, and 27.

All children's parents provided written consent. Participants were predominantly from a middle-class background and all spoke German as their first language. Participation was voluntary, and children and parents received small gifts at the end of the experiment. The study followed the ethical guidelines outlined by the German Psychological Society (Föderation Deutscher Psychologenvereinigungen, 2022).

Procedure and measures

Children and parents participated in a third-person distribution task. For students, the experiment was conducted one-on-one in a quiet room provided by the school. The parents could pick another location (e. g., institute of psychology, home). Participant and experimenter sat opposite each other at a table on which the materials were placed. The experiment lasted 20 min on average.

The experiment used in the present study was intended to allow participants from different age groups to distribute resources based only on contribution, or only on need, or to integrate contribution and need, or to opt for an equal distribution. We based our procedure on the experiment by (Anderson and Butzin 1978, Exp. 3). In that study, the task for the participating children was to help Santa Claus by distributing gifts between two recipients who had helped their mothers with the dishes to varying degrees (contribution) and had different amounts of toys at home (need). To make the stories less dependent on a specific season and more closely aligned with the everyday reality of today's children, we opted for a school setting in which the children were asked to help clean up the schoolyard (contribution)—a task towards a joint goal well-known in everyday school life. As in many other studies, need was operationalized by the amount of candy at home (e.g., Blake et al., 2016; Cowell et al., 2019; Huppert et al., 2019). The participants' task was to distribute 20 pieces of candy, left over from a birthday party at school, between the two recipients.

The within-subjects factors effort and need had three levels each, resulting in nine stories. The first protagonist (A) collected a small, medium, or large amount of garbage, depending on the story. The second protagonist did not collect garbage but had fewer sweets (B), an equal number of sweets (C), or more sweets (D) at home than Protagonist A. The letters in parentheses correspond with the first letter of the protagonists' names in the respective stories (see Figure 1 and Supplementary Table 1).

At the beginning of the experiment, the participants were told that there were no wrong answers and that the experimenter wanted only their opinion. Then three stories (1, 3, and 9, see Supplementary Table 1) were presented as trial runs in order to familiarize the participants with the task. In these, the participants learned both the framing story and the different levels of effort and need. The standardized instructions for the first trial run read as follows: “I am going to tell you a story about children at a school. One day, the children were supposed to be cleaning up the schoolyard. This is Anne (experimenter places the Playmobil ® figure with the letter A on one side of the wooden bar). She put forth a little effort and collected a small amount of garbage. This is Betty (experimenter places the Playmobil ® figure with the letter B on the other side of the wooden bar). She did not put forth any effort and did not collect any garbage. At home, she has fewer sweets than Anne. Here is some candy left over from a birthday party. These are the pieces of candy (pointing to the wooden rings, see Figure 1). The teacher says that you may distribute them between the two children (pointing to two Playmobil ® figures). Please distribute them in a way you think is fair.” For the second trial run, Protagonist A, who worked fairly hard and collected a medium amount of garbage, was compared to Protagonist C, who didn't make any effort and didn't collect any garbage, but had as many sweets at home as A. For the third trial run, Protagonist A, who worked really hard and collected a big amount of garbage, was compared to Protagonist D, who didn't make any effort and didn't collect any garbage, but had more sweets at home than A.

If the participants did not make a spontaneous distribution, the experimenter asked them to distribute “from their gut.” In order to leave no doubt that the result of the protagonist's work was intentional, both effort and outcome (amount of garbage collected) were mentioned in the stories.

After the trial runs, participants were asked if they had any questions. If they did not, the nine stories followed in six different random orders. After each story, the Playmobil ® figures and the other materials were removed and replaced with those from the new story. The experimenter responded to each allocation decision with a neutral “Okay.” No responses such as “good” were allowed so that the experimenter did not give the impression of evaluating the participants.

For the purpose of calculating response consistencies and analyses of variance (ANOVAs) per individual participant (see below), the nine stories were given twice in succession. In total, each participant allocated the pieces of candy 21 times, with the three trial runs not being included in the statistical analyses. The childlike structure of the experiment was explained to the adult participants by telling them that their judgments would be used as standards against which the children's data would be compared.

Three cellophane bags filled with small, medium, or large amounts of trash (reaching mean heights of 3 cm, 7 cm, or 12 cm, respectively, in an 18-cm tall bag) represented the garbage. The sweets at home were symbolized by small (1.8 cm × 3.5 cm × 8.5 cm), medium (4 cm × 6 cm × 10 cm), or large (5.5 cm × 9.5 cm × 16 cm) paper boxes with candies painted on them. The Protagonists A, B, C, and D were symbolized by Playmobil ® figures to which the corresponding letter was affixed (see Figure 1). Each protagonist's gender corresponded to each participant's gender.

Participants' task was to distribute 20 wooden rings, each representing a piece of candy, between the two protagonists. As in Anderson and Butzin (1978), these rings had a diameter of 3.5 cm and a width of 0.8 cm and were centered on a 30-cm-long wooden bar. Protagonist A was always placed at one end, and one of the Protagonists B, C, or D at the other end of the bar. In each trial, the participants were required to spontaneously allocate all 20 rings by sliding them to the ends of the bar.

To determine reliability, we computed the concordance between the two experimental blocks by calculating within-participant correlations. These were transformed into Fisher's z -scores, then averaged and transformed again. Mean r s were.78 for the 10-year-olds, r = 0.98 for the mothers and r = 0.96 for the fathers at T1 and r = 0.79 for the 12-year-olds, r = 0.96 for the mothers and r = 0.96 for the fathers at T2.

Data analytic plan

Data were analyzed in two ways: First, we computed repeated measures ANOVAs on the group level with the within-subject factors time (time 1 and time 2), effort (low, medium, high), and need (lower, same, higher), and the between-subject factor school type (lower voc. track, higher voc. track, academic track). The dependent variable was the number of candies (wooden rings) participants assigned to recipient A, ranging from 0 items to 20 items.

Second, in order to identify the distribution principles each individual participant followed, we computed individual ANOVAs on the basis of the 18 allocation decisions each participant made. Thus, an ANOVA was performed for each participating person, following the standard procedures of information integration theory (Anderson, 1982) and setting p < 0.10 as the significance level. Depending on which main effect became significant in the individual ANOVAs, the participants were divided into the following categories. If only the main effect of need was significant, the child was assigned to the category need only. If only the main effect of effort was significant, the child was assigned to the category effort only. If both main effects were significant, the child was assigned to the category integration. If there was no significant main effect, the raw data were inspected to determine whether this was due to equal divisions or whether the division did not follow a recognizable pattern (no principle). Additionally, the category effort only was assigned when participants allotted, on average, at least three quarters of the candy to the diligent recipient (Protagonist A). This was done because the participants could have based their decisions exclusively on the effort information by giving the most candies to the protagonist who had conducted work—ignoring the differences within the effort category.

Analyses on the group level: children

In order to examine whether the principles underlying the distributive justice decisions changed between 10 years and 12 years, we conducted a 2 × 3 × 3 × 3 repeated measures ANOVA with the within-subject factors time (time 1 and time 2), effort (low, medium, high), and need (lower, same, higher), and the between-subject factor school type (lower voc. track, higher voc. track, academic track). For the effects which violated sphericity, the degrees of freedom were corrected by the Greenhouse–Geisser method if Epsilon was < 0.75. If Epsilon was >0.75, the Huynh–Feldt correction was applied.

The analysis revealed significant main effects for time, F (1,201) = 71.91, p < 0.001, η 2 p = 0.26, effort, F (1.56,314.03) = 112.61, p < 0.001, η 2 p = 0.36, and need, F (1.54,310.23) = 256.04, p < 0.001, η 2 p = 0.56. The main effect of school type was not significant, F (2,201) = 0.55, p = 0.58, η 2 p = 0.005. Additionally, there were significant two-way interactions between effort and school type, F (3.13,314.03) = 2.81, p < 0.05, η 2 p = 0.03, and effort and need, F (3.94,791.84) = 4.81, p = 0.001, η 2 p = 0.02. These were qualified by a three-way interaction between effort, need, and school type, F (7.88, 791.84) = 2.92, p < 0.01, η 2 p = 0.03.

Figure 2 displays the mean number of pieces of candy given to Protagonist A, the child who collected garbage, at both times on the combined basis of his or her effort (low, medium, high) and need (as compared to the other child: lower, same or higher). The data from the first and second measurements were averaged, given the high concordance between the two blocks of the experiment.

Figure 2 shows two main results: First, children at both times considered effort as well as need for their distributive justice decisions, making use of an adding rule: The larger the effort and need exhibited by Protagonist A, the greater the allocation of resources to her or him. Second, at T2, children allotted more candy to Protagonist A in all experimental conditions as compared to T1 (see also Table 1, first two lines). The higher mean value at 12 as compared to 10 years indicates that the work done by Protagonist A was more highly valued by the children when they were 2 years older.

In order to disentangle the interactions between effort, need, and school type, we computed repeated measures ANOVAs with the within-subject factors effort and need for each school type at both times. At T1, for all school types, the main effects of effort (lower voc. track: F (1.73,72.71) = 20.08, p < 0.001, η 2 p = 0.32; higher voc. track: F (1.61,101.63) = 18.27, p < 0.001, η 2 p = 0.23; academic track: F (1.61,159) = 55.34, p < 0.001, η 2 p = 0.36) and need (lower voc. track: F (1.23,15.54) = 25.40, p < 0.001, η 2 p = 0.38; higher voc. track: F (1.39,87.64) = 32.22, p < 0.001, η 2 p = 0.34; academic track: F (1.42,140.31) = 85.34, p < 0.001, η 2 p = 0.46) were significant. Thus, when children were 10 years old and attended elementary school, they considered both effort and need in their allocation decisions, irrespective of the type of secondary schools they were assigned to. The interaction term between effort and need was non-significant in all school types (lower voc. track: F (4,168) = 1.53, p = 0.196, η 2 p = 0.04; higher voc. track: F (3.65,229.92) = 1.81, p = 0.134, η 2 p = 0.03; academic track: F (4,396) = 2.12, p = 0.078, η 2 p = 0.02).

At T2, for all school types, the main effects of effort (lower voc. track: F (2,74) = 8.03, p = 0.001, η 2 p = 0.18; higher voc. track: F (1.66,112.85) = 24.00, p < 0.001, η 2 p = 0.26; academic track: F (1.49,146.38) = 64.35, p < 0.001, η 2 p = 0.40) and need (lower voc. track: F (1.50,55.42) = 37.85, p < 0.001, η 2 p = 0.51; higher voc. track: F (2,136) = 62.67, p < 0.001, η 2 p = 0.48; academic track: F (1.75,171.43) = 166.62, p < 0.001, η 2 p = 0.63) were significant. Thus, when children were 12 years old, they considered both effort and need in their allocation decisions again, irrespective of the type of secondary schools they attended. The interaction term between effort and need was non-significant in all school types (lower voc. track: F (2.77,102.55) = 1.72, p = 0.166, η 2 p = 0.04; higher voc. track: F (4,272) = 2.08, p = 0.084, η 2 p = 0.03; academic track: F (3.75,366.97) = 1.78, p = 0.136, η 2 p = 0.02).

In summary, the students of all school types considered effort and need in their allocation decisions at both times. They also allotted more resources to Protagonist A at T2 as compared to T1 (see Figure 3 and Table 1). For both times, the ANOVAs revealed no significant differences between school types concerning the mean allocation of resources to Protagonist A (T1: F (2,208) = 0.61, p = 0.54; T2: F (2,205) = 0.25, p = 0.78).

Concerning the three-way-interaction between effort, need and school type, Figure 3 shows that children attending lower vocational track hardly considered the different levels of effort in the case of lower need of Protagonist A (dotted line), in contrast to children attending higher vocational or academic track. Lower need of Protagonist A means that she or he has more sweets at home as compared to the other child, who has very few sweets at home. In order to test whether the observed difference between lower vocational track on the one and higher vocational/academic track on the other side is statistically significant, we conducted a 3 × 1 × 3 repeated measures ANOVA with the within-subject factors effort (low, medium, high), and need (lower), and the between-subject factor school type (lower sec., higher sec., academic track) for each measurement point. At T1, only the main effect of effort proved to be significant; F (2, 408) = 14.54, p < 0.001, η 2 p = 0.07, whereas the two-way interaction between effort and school type was not; F (4,408) = 1.21, p = 0.30, η 2 p = 0.01, meaning that students from the three school types did not differ concerning their evaluation of effort. In contrast, at T2, both the main effect of effort and the two-way interaction between effort and school type proved to be significant; F (1.89, 378.80) = 22.71, p < 0.001, η 2 p = 0.10 and F (3.77, 378.8) = 3.23, p = 0.013, η 2 p = 0.03. In a next step, we conducted a 3 × 1 repeated measures ANOVA with the within-subject factors effort (low, medium, high), and need (lower) for each school type at T2. The main effect of effort proved to be significant for students from academic track, F (1.83, 178.84) = 37.98, p < 0.001, η 2 p = 0.28, and higher voc. track, F (2, 136) = 13.31, p < 0.001, η 2 p = 0.16, but not lower voc. track, F (2, 70) = 0.21, p = 0.81, η 2 p = 0.006. Thus, in the condition of lower need of Protagonist A (and higher need of the other child), students from academic and higher vocational track differentiated between the three levels of effort, whereas those from lower vocational track did not.

Analyses on the individual level: children

Mean values can mask centered, all-or-nothing judgments of individual participants. In order to check whether some students focused on only one principle, while others took two into account at the same time, we analyzed each child's 18 allocation decisions individually, thus performing an ANOVA for each participating person (see data analytic plan). Results of the individual ANOVAs for both times of data collection are depicted in Table 2.

The first two columns of Table 2 show the results for all participants at 10 years and 12 years. More children relied on no principle, need only and equality at 10 as compared to 12 years. Concerning effort only, there was a slight increase between 10 years and 12 years. The biggest difference can be observed for integration. A third of the children integrated effort and need when 10 years old, as compared to more than 50% at age 12. Summing need (percentages of need only plus percentages of integration) and effort (percentages of effort only plus percentages of integration; see the last two lines of Table 2) shows that need was clearly the dominating allocation criterion at 10 years, whereas the ratio between the two allocation criteria need and effort is balanced at 12 years.

Additionally, we examined the kind of changes in distributive justice principles between the two times. A Bowker-Test indicates that there are significant changes in the applied distribution principle between the two times of data collection (χ 2 (10) = 34.15, p < 0.001). To determine whether a pattern of change could be identified between the ages of 10 and 12, we compared, for each child, the criteria they had used to allocate the resources at both ages. 20% of the children who relied on no principle at 10 years did so also at 12 years, 12% of them changed to effort only, 28% changed to need only and 40% to integration. Among the children who rewarded effort only at age 10, at age 12, 4% changed to no principle, 39% remained at the effort principle and 57% changed to integration. In the case of children who had made their allocation decision at age 10 based on need only, at age 12, 11% changed to no principle, 12% changed to effort only, 37% rested in the need category and 40% changed to integration. Of the children who integrated at 10 years, at 12 years, 4% changed to no principle, 14% changed to effort only, 12% changed to need only and 70% integrated also at age 12. Among the children who relied at 10 years on equality, at 12 years, 17% changed to no principle, 17% changed to effort only, 8% changed to need only, 50% changed to integration and 8% remained at equality. This means that regardless of the criteria used to allocate resources when the children were 10 years old, the majority of them integrated effort and need by the time they were 12.

Table 2 also shows the results of the individual ANOVAs grouped by school type. For both 10 years and 12 years, Fishers exact tests yield no significant relationship between distribution criterion and school type (T1: p = 0.45; T2: p = 0.53). In all three types of school, equal distributions hardly occurred. The number of students who relied on need only decreased, the number of those who relied on effort only stayed stable on a comparatively low level and the number of children who integrated effort and need increased to approximately 50%.

Analyses on the group level: parents

For the analysis of parents' data, we computed 3 (effort) × 3 (need) × 2 (gender) repeated-measures ANOVAs for parents at T1 and T2, respectively. Gender was included here because the matches between children and parents (see below) were determined for mothers and fathers separately. For the effects which violated sphericity, the degrees of freedom were corrected by the Greenhouse–Geisser method if Epsilon was smaller than 0.75. If Epsilon was greater, the Huynh–Feldt correction was applied. The analyses for parents at T1 revealed significant main effects of effort, F (1.74,185.93) = 30.18, p < 0.001, η 2 p = 0.22, and need, F (1.46,156.7) = 30.8, p < 0.001, η 2 p = 0.22, but not for gender, F (1,107) = 2.24, p = 0.14. There were no significant two- or three-way-interactions. At T2, again, there were significant main effects of effort, F (1.59,223.71) = 33.57, p < 0.001, η 2 p = 0.19, and need, F (1.40,197.57) = 63.39, p < 0.001, η 2 p = 0.31, but not for gender, F (1,141) = 0.87, p = 0.35. There were no significant two- or three-way-interactions. Thus, at both times, parents considered effort as well as need for their distributive justice decisions. Figure 4 displays the mean number of pieces of candy given to Protagonist A by parents on the combined basis of need and effort.

Figure 4 shows that parents, just like their children, at both times considered effort as well as need for their distributive justice decisions, making use of an adding rule: The more effort Protagonist A put in and the greater her or his need, the more resources she or he received. A linear mixed model revealed that the mean number of candies allotted to Protagonist A did not differ between Time 1 and Time 2 (F [1,146.33] = 1.09, p = 0.30; see Table 1). As for the children, we computed additional ANOVAS that were run for each individual participant again.

Analyses on the individual level: parents

Parents mostly allocated the resources at both times either according to the information about effort only or they integrated effort and need (see Table 3). Summing the percentages for need only plus integration and for effort only plus integration (see the last two lines of Table 3) shows that effort is clearly the more important allocation criterion for the adults as compared to need.

Matches between children and parents

On the basis of the individual analyses (Tables 2 and 3), we determined the proportion of matches between children's and parents' distributive justice decisions for each time. Since for 20 children at T1 and for 32 children at T2, both parents participated, we determined the matches for mothers and fathers separately. At T1, 68% of the distributive justice decisions of mothers and children did not match. The matches were distributed as follows: Both no main effect (1%), both allocated based on effort information only (8%), both allocated based on need information only (4%) and both integrated (19%). The number of non-matches between fathers and children was even higher; it totaled 88%. The remaining percentages were spread between both effort (4%) and both integration (8%).

At T2, 69% of the distributive justice decisions of mothers and children did not match. The matches were distributed as follows: Both allocated based on effort information only (5%), both allocated based on need information only (2%) and both integrated (24%). The number of non-matches between fathers and children was 70%. The remaining percentages were spread between both effort (3%), both need (3%) and both integration (25%). In sum, there was no match between children's and parents' distributive justice decisions for more than two thirds of the mother-child and father-child pairs.

This study used a longitudinal approach to examine the criteria applied by children aged 10 and 12, as well as their parents, when allocating a resource fairly between two protagonists who systematically differed in effort and need. One protagonist had always made an effort and achieved a small, medium, or large amount, while the other protagonist had made no effort and had not achieved anything, but was less, equally, or more needy than the first protagonist. In an experimental setting, each participant made 18 distribution decisions per time. The main aim of the study was to find out on the basis of which criteria (effort, need, integration of effort and need, equality) the children would make their distributive justice decisions at ages 10 and 12 and how possible changes in this period could be explained.

At the age of 10, children gave less of the resource to the protagonist who collected garbage as compared to the age of 12. This means that the importance of the effort criterion increased between 10 years and 12 years. This result was confirmed by analyses at the level of the individual children: while at age 10, the need criterion was more often the basis for distribution decisions as compared to the effort criterion, the ratio between the two criteria was balanced at age 12. However, this was not because more older children allocated resources based on effort information only, but because more of them integrated both criteria, i.e., they took effort and need into account simultaneously. In searching for the reasons for this development, three factors were considered: the cognitive development of the children, parental distribution preferences, and the school environment.

Cognitive development

Between the ages of 10 and 12, the proportion of distribution decisions that integrated need and effort rose from one-third to one-half. Since considering two variables at a time is cognitively more challenging than focusing on one variable only, this result points to processes of cognitive development and thus supports the assumption of information integration theory, according to which the ability to integrate information increases with age due to cognitive development (Anderson, 1996).

Looking at the distribution principles of equal distribution, need, and effort individually, it is striking that equal distribution played only a minor role. This can probably be explained by the fact that comparisons between the protagonists were constantly being made in the experiment. As a result, attention was probably focused on the different degrees of effort or need, which meant that the principle of equal distribution was given less consideration.

Need was the only criterion for the distribution decisions in one-third of the 10-year-old children; this proportion fell to about one-fifth at the age of 12. Effort as the only criterion was the basis for the allocation decision in only 13% of 10-year-olds and 16% of 12-year-olds. Adding these values to those for integration (see the last two rows of Table 2), the criterion of need clearly dominates over the criterion of effort for 10-year-olds, whereas for 12-year-olds there is an almost equal balance between the two criteria. This result replicates the cross-sectional data reported by Kienbaum and Mairhofer (2022). The increasing importance of the effort criterion between 10 years and 12 years, which is also evident in the age-related increase in the mean allocation of resources to the diligent protagonist, is likely to be related to the growing understanding that effort is expected at school. Distributive justice norms that go beyond equality are likely to become increasingly important as students progress through their school years (Schmidt et al., 2016); accordingly, children's understanding that they have to work hard to be successful should increase with every year in school. This interpretation is also supported by the even higher mean allocation rates of parents, who are usually confronted with the principle of effort or merit on a daily basis in adult life.

While the assumptions of information integration theory are supported by the data from this study, the developmental sequence described by Damon (1990) is refuted insofar as this author assumed that need is only taken into account after contribution in the course of development, as it is the comparatively more difficult criterion. The data obtained here suggest that need dominates as a criterion during childhood and that effort only “catches up” with need in early adolescence. One important difference between the studies by Piaget (1954) and Damon (1990) and the present one is that we asked our participants for intuitive judgments, whereas Piaget and Damon asked them to reason. Reasoning is a more conscious process than deciding intuitively (Reyna and Brainerd, 2011). When identifying reasons for a particular distribution being fair or unfair, children may rely on the most salient reasons they encounter in daily life, especially those that are socially desirable. For schoolchildren, this could be diligence rather than need, which may explain the developmental sequence found by Damon (1990).

The results of the present study also do not support the conclusion reached by Zhou et al. (2023, Exp. 2) that children, as they get older, come to prioritizing need over contribution. Several factors may play a role here: First, Zhou et al. (2023) examined developmental processes during childhood, whereas the present study focused on development from childhood to adolescence. For this reason, the results cannot be directly compared. Second, different resources were examined: medication versus sweets. Medications represent a necessary resource, which presumably reinforces the significance of the need criterion. Furthermore, in Zhou et al. (2023), the statistical analyses were conducted only at the level of mean values, so no conclusion can be drawn as to whether integration occurred or not. Finally, cultural differences could also play a role (Schäfer et al., 2015): According to Wong and Nunes (2014), Chinese parents praise their children for being hardworking and view playing as a pointless activity. Successful parenting is determined by children's academic performance. This could mean that the criterion of contribution gets a priority earlier for children from China as compared to those from Germany. Cross-cultural studies are highly desirable to clarify this point.

Value socialization: parents

At both times of measurement, the parents based their allocation decisions either exclusively on effort information or they integrated effort and need. Overall, the effort principle clearly dominated the need principle among the adult participants. In contrast, the need principle clearly dominated the effort principle among the children when they were 10 years old, while the ratio of the two principles was balanced 2 years later, at age 12. Given this different pattern of decisions, it is not surprising that the allocation decisions of at least two-thirds of the mother-child and father-child pairs studied did not match, neither at 10, nor at 12 years. The parental distribution principles therefore do not appear to be the cause of the children's distributive justice decisions.

This finding contrasts with studies that have demonstrated an effect of parental modeling on children's distributive justice decisions and preferences (Blake et al., 2016; Geraci et al., 2026; Rottman et al., 2020). It should be noted, however, that the reported effects were only short-term, occurring either immediately (Blake et al., 2016; Geraci et al., 2026) or within 2 weeks to 4 weeks (Rottman et al., 2020) following the experimental manipulation. No conclusions can be drawn regarding long-term effects on children, as postulated in the present study. There is a need for further research in this area.

It could further be argued that parents and children interpreted the experimental situation differently: while sweets are certainly desirable for children, parents may consider them a dispensable luxury item. Kienbaum and Mairhofer (2022) investigated this question by comparing the distribution decisions of children and adults in two experiments. In the first, need was operationalized using candy, and in the second using toys. Although both do not represent necessary resources (Essler et al., 2020; Meidenbauer et al., 2018; Rizzo and Killen, 2016; Rizzo et al., 2016), from an adult's perspective, a child with fewer toys may be considered needier than one with fewer sweets. In both experiments, the distribution patterns described above occurred, leading to the conclusion that the differences between children and adults do not depend on the operationalization of need—at least within a continuum of more or less luxury resources.

In addition, the context in which the stories took place could also play a role. Perhaps the match between parents and children would be higher if it had been a distribution within the family context. Possibly it is the experiences that children have here—e.g., when it comes to decisions about distributions between siblings (Tisch and Gutfleisch, 2023)—that are of particular importance for the development of their distributive justice decisions.

Based on the argument that socialization should be more effective the longer it lasts, one might assume that a match between parents and children could be stronger in later adolescence. This argument is supported by the fact that the number of mother-child and father-child pairs who both integrated increased between the ages of 10 and 12. Further research is needed to determine whether this trend continues into adolescence and whether agreement in categories other than integration would also increase.

Value socialization: school environment

The third possible explanation for the development of students' distributive justice decisions was the type of secondary school they attend. In the German school system, a selection process takes place at the age of 10, which distributes children into three different types of schools: lower vocational track, higher vocational track, or academic track. The assumption was that these three types of schools offer different developmental environments for children, which in turn can lead to different value preferences in distributive justice decisions. For example, Kienbaum's (2013) study from Germany showed that children from lower vocational track schools based their distribution decisions less on the effort criterion than those from academic track schools. This result was not replicated in the current study, as the increase in the average resource allocation between the ages of 10 and 12 was similar in all three school types. Only in one condition—the one in which the protagonist who did not collect garbage had particularly few candies—did the children from the lower secondary school ignore the extent of the other protagonist's effort, in contrast to the two higher school types. Thus, for the children attending lower vocational track school, the different levels of effort did not play a role in a situation of high need, which can possibly be explained by the fact that they are more familiar with a state of high need as compared to the children attending higher vocational or academic track (Wößmann et al., 2023).

At the level of individual children's decisions, there were also more similarities than differences between the school types, as in all three groups, the number of children who integrated effort and need increased between the ages of 10 and 12. In contrast to the study by Kienbaum (2013), there was no difference between lower vocational track and academic track schools at this level either. One possible explanation is that the participating children from lower vocational track schools were subject to a selection process, in the sense that it possibly could have been primarily parents from comparatively better-educated families within this type of secondary school who allowed their children to take part in this longitudinal study. In contrast, the 12-year-old children from the lower vocational track school in Kienbaum's (2013) cross-sectional study all came from one class. This means that they presumably represented a wider range of family backgrounds as compared to the children from the lower vocational track school in the present study, because even though the children's socioeconomic background is generally lower than that of students attending academic track schools, there is always some variation within a single class. Therefore, it cannot be ruled out that it was the more educated parents within the lower vocational track schools who gave their children permission to participate in the longitudinal study. This interpretation is also supported by the fact that in the present study, 12-year-olds from lower vocational schools based their decisions on distributive justice more often on the criterion of effort than on the criterion of need, in contrast to students from the other two types of schools. Future studies should pursue this explanatory approach and collect more data on the children's family background and academic performance.

Limitations

One limitation of this study consists in the fact that the decisions between effort and need were all made within a single context. Whether the developmental sequence would be similar if the resource in question had been a necessity rather than a luxury (Essler et al., 2020; Meidenbauer et al., 2018; Rizzo and Killen, 2016; Rizzo et al., 2016), or if the activity had taken place within a family context rather than a school setting, or if the work had not been towards a joint but an individual goal is a question that requires further research.

Further, this study focused on intuitive allocation decisions, not on the reasons behind them. It would be interesting to compare the allocations and the reasons given for them in order to analyze whether they match or not. Further, we only used a third-party allocation task. In order to find out whether children also follow the principles identified here when they themselves are affected by the allocation of resources, additional studies with a first-party design would need to be conducted.

Another critical aspect is the composition of the parental sample. Almost two-thirds were parents of children attending an academic track school, whereas the proportion of parents with a child in a lower vocational track school was only 12%. Since it cannot be ruled out that parents from different socioeconomic backgrounds impart different values to their children, future studies should aim for a more balanced ratio here.

Finally, the results of this study are limited by the relatively narrow age range that was examined. Although the age range between 10 years and 12 years is of great importance in Germany, as it is when children transition to secondary school, it would nevertheless be of considerable interest to examine older students as well. This would clarify whether cognitive development processes continue to determine the development of distributive justice decisions, or whether the influence of parents or school type becomes more noticeable with age. When looking at the data from parents, it is striking that, although we can safely assume that adults are capable of integrating multiple pieces of information into a judgment, more than a third of them distributed the resource based exclusively on a single piece of information, namely the effort involved. In addition, 10% of parents divided the sweets equally, which is remarkable in that the criterion of equality is considered typical for early childhood. This argues in favor of allocation decisions based on values. Thus, future research should investigate from what point in development values determine distribution decisions.

In summary, based on the data from this longitudinal study, the question of the developmental factors underlying decisions regarding distributive justice during the transition from childhood to adolescence can best be answered in terms of an increasing capacity for integration, i.e., cognitive developmental processes.

These results expand the current state of research in that we can say that the allocation criteria of effort and need are not only used more frequently with age, but that they become increasingly integrated with each other between childhood and adolescence. Summarizing the results of this and other studies (Cowell et al., 2019, 2025; Damon, 1990; Huppert et al., 2019; Piaget, 1954; Rizzo and Killen, 2016; Schmidt et al., 2016), it can be concluded that it is primarily cognitive processes that determine the development of distributive justice decisions until early adolescence. The development of distributive justice decisions from early adolescence onwards is a task for future research, which would further contribute to clarifying the exciting question of what people perceive as fair and why.