Methodology

We recruit various experimental methods, including violation of expectation paradigms, eye-tracking paradigms, and EEG (Electroencephalogram), as tools to investigate infants’ understanding of the social world.

Violation of Expectation Paradigms

This method uses infants’ looking time at different events to examine whether the events violate their expectations. If an event violates infants’ expectations, they usually look longer at it because they are either surprised or need more time to process what just happened. For example, when a screen rotates in depth through a 180° arc, if a box is placed in the path of the screen, the screen should only rotate through a 120° arc until it reaches the hidden box (possible event). However, if the screen rotates through a full 180° arc as though no box blocked its path (impossible event), infants look longer at this impossible outcome (see the figure below, Baillargeon et al., 1985). Similarly, researchers have found that infants look longer at unfair distributions versus fair distributions, suggesting that infants expect resources to be distributed fairly (Ziv & Sommerville, 2017). Numerous studies have found that infants look longer at impossible or unlikely events. Following this logic, we use this method to examine infants’ expectations about different physical and social events.

Eye-tracking paradigms

Eye-tracking is another way to investigate infants’ minds. An eye tracker uses infrared light and cameras to monitor and record the movement and position of the eyes, providing data on where a baby is looking (see Figure 1). Using this method, we can measure infants’ looking behaviors more precisely and explore infants’ anticipations in specific situations. For example, to examine whether infants understand goal-directed actions (i.e., reaching for a specific object indicates the desire to get the object) and make corresponding predictions, we familiarized infants with a video of a hand reaching for a red ball rather than a green toy. Then, the locations of the two objects were swapped, and the hand made an incomplete reach between the two objects. With eye-tracking, we found that infants are more likely to make their first look from the hand to the red ball, suggesting that infants understand the goal of the hand is the red ball and anticipate the next movement of the hand is to get the red ball (see Figure 2, Cannon & Woodward, 2012).

Figure 1

Figure 2

EEG (Electroencephalogram)

EEG is a safe, passive, and non-invasive procedure that measures and records the electrical activity of a baby’s brain. Small sensors (electrodes) are placed on the infant’s scalp to detect brain waves. This technique provides valuable insights into the function and development of early brains and has been widely used in infant neural studies.