In one study, an experimenter announced her intention to find a "gazzer" (using a novel label for a novel object). she then picked up one of two objects and showed obvious disappointment with it, when she gleefully seized the second object, children correctly inferred that it was the "gazzer." this study demonstrates that children use in word learning.

A person's emotional cues.

Explanation:

The individual can recognize the other individual's  intention by his behavior or the facial expression. The cues are the quiet effective to understand the speaker.

The researcher wants to find the gazzer. The children inferred that second object is gazzer. Here, the children uses the the emotional cues. The cues means that the work used by the speaker and his emotions by looking at his facial expressions.

Thus, the correct answer is person's emotional cues.