Of the most central and essential aspects of humanity, our ability to empathize with one another may be the mental function holding us together.

In studying human development from its most infantile stages to maturity, scientists have felt that sympathy — the ability to feel concern for others — is elemental but poorly understood. Although philosophers and artists have for centuries offered insight into its origins, the progression of the capability in human infancy remains fairly mysterious.

Now, investigators at the University of London say that Infants as young as 10 months of age demonstrate a basic form of sympathy toward others, which may serve as a foundation for further development in later stages.

In a study published Wednesday in the journal PLOS One, 10-month-old infants were filmed while watching animated video depicting a victim and aggressor, a blue ball and a yellow cube.

In the first video sequence, infants watched the blue ball chasing the yellow cube, which it attacked and violently crushed at the end, whereas a later sequence switched the roles of the two geometric shapes. Half of the infants in a control group watched video sequences with no contact between the geometric shapes, which moved independently of each other at varying speeds.

After confirming by video that an infant had indeed looked at both geometric shapes in the video, researchers were then able to test whether the 10-month-old would judge representations of those shapes in another context. A research assistant, who had no knowledge of the experiment, then presented the infants with a choice between three-dimensional representations of the two shapes, both placed on a table at a set distance apart.

Frames from the video stimuli show a yellow cube chasing a blue ball, or vice versa. [PLOS One]

"We found that the infants preferentially reached for the victim over the aggressor" after viewing the video in which violence had occurred, "indicating that infants formed different evaluations for figures based on the nature of their previous interactions and preferred others in distress," the researchers wrote in the study.

"These results cannot be explained by low-level perceptual interpretations at least such as movement speed, kinetic momentum, and deformation, because they were the same for the two figures."

So with confidence, the researchers figured the infants preferred the victim shapes, but wondered whether that preference was motivated not by sympathy but a fearful desire to avoid the aggressor.

To discern between the two, researchers then added a third geometric element into the mix, this time testing 24 10-month-old infants. In this experiment, the third object moved independently of the other two shapes, with the same movement speed, momentum, but with a subtle difference incorporated to differentiate from the victim and aggressor.

Across both experiments, however, infants preferred victims to aggressors.

"In investigating sympathetic behavior in preverbal 10-month-old infants, we demonstrated that they preferentially reached for victims as opposed to aggressors and neutral objects after observing third-party social interactions involving aggression," the researchers wrote.

"These findings indicate that preverbal infants show a sympathetic response toward attacked others who displayed no distress, suggesting that rudimentary sympathy for others based on an evaluation that is beyond merely a response to distressed others through emotional contagion occurs earlier in development than previously assumed."

Although emotional contagion may serve as the mechanism for this response, the researchers concluded that something else — perhaps sympathy — was in play, given the lack of emotional signaling in the experiments from victim shapes. To evaluate each character in the scenarios, including victims, aggressors, and neutral bystanders, the infants needed to understand the intentions of the characters as well as the causal relationship between them.

"We suspect that because infants discriminated between the roles of the geometric figures, they had some understanding of agency," which may serve as the underpinnings of a sympathetic response, the researchers wrote.

Although some controversy exists over how to interpret these types of experiments, investigators here concluded that infants in that age range at least possess a rudimentary form of sympathetic response toward others.

Source: Kanakogi Y, Okumura Y, Inoue Y, Kitazaki M, Italkura S. Rudimentary Sympathy in Preverbal Infants: Preference For Others In Distress. PLOS One. 2013.