Final answer:
Arched eyebrows during a speech usually indicate confidence and assertiveness, enhancing the speaker's authority and presence.
Step-by-step explanation:
During a speech, arched eyebrows can be associated with confidence and assertiveness. This non-verbal cue is typically interpreted as a sign that the speaker is engaged and confident in what they are communicating. Arched eyebrows can elevate the perceived authority of the speaker and contribute to a more commanding presence.