A recent study explored whether 18-month-old infants can adjust their communication based on what they believe their partner knows. The findings suggest that even at this young age, infants tailor their pointing gestures to provide relevant information when their partner lacks it. This ability reflects a sophisticated understanding of others’ mental states, highlighting the early development of skills crucial for human communication. The findings were published in Open Mind: Discoveries in Cognitive Science.
Human communication relies on the ability to share and interpret information effectively. This often involves understanding what others know—or don’t know—and adjusting behavior accordingly. While adults naturally modify their communication to suit their audience, little is known about when this skill begins to develop. Researchers aimed to determine whether infants, who are just beginning to communicate, could similarly adapt their actions based on others’ knowledge.
“Human communication is unparalleled in the animal kingdom. To understand what makes it unique, we can investigate how it differs from animal communication systems,” said study author Tibor Tauzin, a postdoctoral researcher affiliated with the Babelfisch Lab at the University of Vienna.
“We hypothesized that human infants already have the ability to recognize that, in order to communicate effectively, they must consider the knowledge others possess. This led us to investigate whether infants point more accurately to an object when interacting with someone who has incorrect or no knowledge about it.”
The research consisted of three experiments, each testing how infants adapted their gestures depending on what their partner could see or knew.
In Experiment 1, the researchers investigated whether 18-month-old infants could adapt their pointing gestures to make their intentions clear in situations where a simple point could be ambiguous. Infants were seated across from an experimenter at a table, with two objects—one being the “target” that the infant wanted and the other a “distractor”—placed on the table. The objects were arranged in three different ways: the target closer to the infant, the target farther away but behind the distractor, and the target alone.
The experimenter asked the infant to show her where the desired object was. If the infant pointed to the target, the experimenter activated it to produce lights and sounds, providing positive feedback. If the infant pointed to the distractor, which could not activate the effects, the experimenter expressed mild disappointment.
The results showed that when the target was behind the distractor, infants spontaneously modified their gestures to avoid ambiguity, pointing higher or at an angle to clearly indicate the desired object. This demonstrated that infants could adjust their communication based on the spatial arrangement of objects to ensure clarity.
In Experiment 2, the researchers tested whether infants could take into account what their communicative partner did or did not know about the objects’ locations. This time, the objects were hidden under opaque cups. The infants interacted with two experimenters: one who had seen the objects being hidden and one who had not. In one condition, the same experimenter who hid the objects returned and asked the infant to indicate the target’s location. In another condition, a different experimenter, who had no prior knowledge of the objects’ placement, entered and made the same request.
The researchers found that infants pointed more frequently at the target and used clearer, more modified gestures when interacting with the uninformed experimenter, suggesting that they recognized the partner’s lack of knowledge and adapted their communication to fill in the informational gap.
In Experiment 3, the researchers examined whether infants could correct a communicative partner who held incorrect information about the target’s location. After one experimenter placed and hid the objects, another experimenter entered and visibly swapped their positions under the cups. In one condition, the first experimenter returned, unaware of the swap, and asked the infant to indicate the target’s location. In another condition, the experimenter who had witnessed the swap returned and made the same request.
The findings revealed that infants were more likely to point at the target and use modified gestures when interacting with the misinformed experimenter. This indicated that infants understood the experimenter’s incorrect belief and adjusted their communication to correct it.
“Our findings suggest that human infants can understand when their communicative partner has inaccurate or no information about a relevant fact,” Tauzin told PsyPost. “Moreover, they do not merely recognize that someone is missing crucial information; they actively try to help their communicative partners by providing additional details.”
“In this way, infants communicate in a manner similar to adults, who share more detailed information with others lacking the relevant background knowledge. For example, an adult might say, ‘The tool is in the bottom drawer in the cabinet on the left-hand side,’ rather than simply stating, ‘The tool is in the drawer’ when their partner is ignorant about the fact that the tool can be found in one specific place.”
The results of these experiments have significant implications for understanding early human communication. They suggest that even at 18 months, infants possess a sophisticated ability to infer and act upon their communicative partner’s mental states, including their knowledge and beliefs.
“One of the most striking aspects of our study is that, according to the standard view, only children aged 4 and older are thought to have the ability to recognize when others possess incorrect knowledge about a particular fact—an ability known as ‘mentalization,” Tauzin explained. “However, our results suggest that even infants can understand when someone holds a false belief about reality and take this into account during interactions with that person.”
The study sheds new light on the communicative abilities of 18-month-old infants but there are limitations to consider. First, the study focused on a specific form of communication (pointing) in a controlled setting. It is unclear how these skills generalize to other forms of interaction or more naturalistic environments. Second, the sample size was relatively small, with 24 to 48 participants per experiment, though appropriate for the study’s design.
“The aim of our study was to determine whether human infants are able to recognize that others have incorrect or incomplete information about a fact during a communicative interaction with an adult,” Tauzin noted. “Our findings demonstrate that infants can use mentalization to communicate effectively with others. However, our results do not suggest that infants can use mentalization for other purposes, such as predicting the future behavior of others based on their knowledge and beliefs.”
Future research could explore whether these abilities extend to younger infants or involve other types of communicative gestures, such as vocalizations. Additionally, examining the neural mechanisms behind this behavior could provide insights into the development of human social cognition.
“Our research group also conducted a similar experiment with non-human primates (chimps, gorillas, orangutans, and bonobos), where we found that, in contrast to humans, they cannot understand when their communicative partner is ignorant of a relevant fact,” Tauzin added. “Even when motivated to share precise information they alone possessed about the location of hidden food, the primates failed to do so. This suggests that human communication may be fundamentally different from that of other animals, as humans have the ability to mentalize—that is, to understand that knowledge and beliefs is guiding the behavior of others.”
The study, “Infants Produce Optimally Informative Points to Satisfy the Epistemic Needs of Their Communicative Partner,” was authored by Tibor Tauzin, Josep Call, and György Gergely.
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