Final answer:
Facial expressions are the most likely type of nonverbal communication to be similar across different cultures because basic emotions are universally recognized, despite cultural differences in display rules.
Step-by-step explanation:
Which type of nonverbal communication is most likely to be similar in different cultural and ethnic groups is facial expressions. These are often part of a person's subconscious and can be universally recognized emotions such as joy, represented by a smile, or sadness, represented by crying. Despite cultural differences in display rules that may dictate how and when emotions can be expressed, the ability to produce and recognize facial expressions of emotions appears to be universal. In contrast, other forms of nonverbal communication like hand gestures, posture, and eye contact can vary significantly between cultures. A thumbs-up gesture may convey positivity in one culture, while it may be considered rude or an offense in another. The context of eye contact can also differ; while it may signify engagement and credibility in some cultures, in others, it might be deemed aggressive or inappropriate. Therefore, facial expressions emerge as the most widely understood form of nonverbal communication across different cultures.