In comparison with those who read the transcripts, the evaluators who heard pitches judged the candidates to have greater intellect (to be more rational, thoughtful, and intelligent), on average. They also liked the individuals more, had a more positive overall impression, and — perhaps most important — were more interested in hiring the candidates. Evaluators who saw the videos appeared to be even more favorably impressed, but there was no statistically significant difference between the evaluations of video and audio.

Source: The Science of Sounding Smart