Why help others? Insights from rodent to human early childhood research

Abstract

Helping behavior are actions aiming at assisting another individual in need or to relieve their distress. The occurrence of this behavior not only depends on automated physiological mechanisms, such as imitation or emotional contagion, that is, the individual's emotion and physiological state matching with others, but also needs motivation to sustain. From a comparative and developmental perspective, we discover that the motivation for helping behavior has a deep foundation both phylogenetically and ontogenetically. For example, empathic concern for others, relieving personal distress and the desire for social contact are universal motivations across rodents, non-human primates and human early childhoods. Therefore, a circle-layered model integrating evidences for motivation for helping behavior from rodent to human early childhood research is proposed: the inner circle contains the emotional-behavioral system and the outer circle contains the affective-cognitive system. The application of this model has significance for both behavioral neuroscience research and cultivating prosocial behavior in human society.

Keywords: comparative cognition; helping behavior; human early childhoods; motivation; primates; rodents.

FIGURE 1

Helping behavior experiments in rodents. (A) In this experiment, a black rat was in distress and a red rat was the free rat (helper). The free rat had the ability to press the lever bar to rescue the distressed rat, who was suspended in the air by a harness (Rice and Gainer, 1962). (B) In this experiment, a black rat was either in distress or not, and a red rat was the free rat (helper). When the distressed rat was trapped in the water (left panel), the free rat could learn to rescue the trapped distressed rat by pulling the lever. As sessions progressed, the latency to help decreased. In contrast, the free rat did not pull the lever when the rat was not in distress in the ground area (right panel) (Sato et al., 2015). (C) In this experiment, a black rat was trapped in the left restrainer and in need of help, with some chocolate in the right restrainer. The red rat was the free rat (helper). When faced with the choice of rescuing the conspecific and enjoying the delicious food, the free rat chose to first rescue the trapped conspecific and share the food with it (Bartal et al., 2011). (D) In this experiment, a black rat was trapped in the restrainer and in need of help, and the red rat was the free rat (helper). The gray area was the darkroom that allowed the free rat to escape from the helping situation. In the upper panel, the darkroom door is closed, and the free rat cannot enter. But in the lower panel, the darkroom door is open, and the free rat can enter. Compared with rats in the non-escapable group (upper panel), rats in the escapable group (lower panel) had a longer delay in opening the door to help rescue the trapped rat (Carvalheiro et al., 2019). (E) In this experiment, a black rat was trapped in the restrainer and in need of help, and the red rat was the free rat (helper). Even when unable to make social contact after helping, the free rat still chose to open the door for the trapped rat in the restrainer (Bartal et al., 2011). (F) In this experiment, the black rats in need of help were placed at both ends of the E maze (left end: the rat was trapped in the wet goal box; right end: the rat was trapped in the dry goal box). The red rat in the middle was the free rat (helper) and could choose freely. It was found that the free rat preferred to interact with the rat in the wet goal box (Schwartz et al., 2017).

FIGURE 2

Helping behavior experiments in non-human primates. (A) The red chimpanzee acted as the subject, the black chimpanzee as the companion, and figure in black was the experimenter. The red circle represented the food reward. The pro-social selection paradigm was employed where the subject was given a box of tokens that could be exchanged for food. Tokens included pro-social and pro-self tokens, with their meanings taught beforehand. Pro-social tokens resulted in rewards for both the subject and their companion, whereas pro-self tokens only yielded a reward for the subject. Results showed that chimpanzees predominantly chose pro-social tokens (Horner et al., 2011). (B) The red chimpanzee acted as the subject, and the black chimpanzee was either a friend or neutral peer. The red circle represented the food reward. The subjects were familiar with using tools to deliver food beforehand. During the test, they could choose to pull the rope to deliver food to either their friend or the neutral peer. Results showed that chimpanzees preferred to help their friends obtain food (Engelmann et al., 2019). (C) The red chimpanzee acted as the subject, and the black chimpanzee was the recipient. When the subject pressed the button, juice would flow out of a distant fountain, but only the recipient could drink it. Results showed that the majority of chimpanzees would continuously press the button (van Leeuwen et al., 2021). (D) The red marmoset acted as the subject, and the black marmoset was the recipient. The red circles represented the food reward. The altruistic paradigm on the left showed that when the subject stepped on the platform, only the black marmoset next to it received food. The cooperative paradigm on the right showed that when the red and black marmosets pulled the rope simultaneously, they could obtain food together (Martin et al., 2021).

FIGURE 3

Helping behavior experiments in human early childhoods. (A) The red figure represented the toddler actor, and the blue figure represented the toddler receiver. The red circle was the reward. The actor could choose to pull the lower pro-social pull rod, which would benefit both themselves and the receiver, or the upper pro-self pull rod, which would only benefit themselves. The experiment found that 2.5-year-old toddlers pulled more pro-social levers, indicating a preference for pro-social behaviors (Sebastián-Enesco et al., 2013). (B) The red figure represented the infant actor, and the black figure represented the experimenter. The experiment observed the infants’ instrumental helping behavior when the experimenter pretended that something had fallen and required assistance. The study found that additional rewards decreased the infant’s helping behavior (Warneken and Tomasello, 2008). (C) The red figure represented the actor, and the black figure represented the receiver. The experiment investigated whether children would help their friends or peers when given a choice to assist only one. The results revealed that young children helped their friends more but also helped their non-friend peers (Engelmann et al., 2019). (D) The red figure represented the actor, who had ten stickers that could be kept or given away. The stickers that the actor kept were put in white envelopes, while the stickers given to others were put in blue envelopes. The results indicated that both autistic and neurotypical children demonstrated altruistic tendencies (Peterson and Wellman, 2022). (E) The red figure represented the actor, the black figure at the table represented the experimenter, and the other black figure was the bystander of the same age as the actor. The experimenter pretended to spill water and required assistance. There were no bystanders in the left picture, two bystanders in the middle picture, and two bystanders in the right picture (but there were obstacles preventing them from helping the experimenter). The results showed that children were more likely to help the experimenter when there were no bystanders or when bystanders were unable to help (Plötner et al., 2015).

FIGURE 4

The circle-layered model of motivation for helping behavior. This figure illustrates the circle-layered model of motivation for helping behavior. According to this model, at the core of helping behavior is the emotional contagion mediated by the perception-action mechanism, which allows individuals to perceive and understand the emotional state of the individual in need of help. This mechanism leads to two different emotional experiences, empathic attention to others or personal distress in oneself, which can motivate individuals to help alleviate their own distress or that of others. The second-layer motivation for helping behavior is the expectation of rewards, which includes both extrinsic and intrinsic rewards. Extrinsic rewards can include social interaction, material rewards, or praises, while intrinsic rewards can include the positive experiences and sense of pleasure generated by helping others. These rewards not only act as positive outcomes of helping behavior but can also be transformed into a motivation for helping behavior. The third and fourth layers of motivation for helping behavior are mediated by the more advanced affective-cognitive system. These layers include abiding by social norms and pursuing long-term affective goals, such as pride and a sense of meaning. Overall, this model suggests that the motivation of helping behavior may evolve and develop from the emotional-behavioral system to the affective-cognitive system, and from the inner layer to the outer layer, which is likely shared by humans and non-human mammals.