By ALEX MINDLIN

After watching an online video for a full minute, 44.1 percent of viewers will have clicked away, according to Visible Measures. But an outsize slice of that loss occurs in the first 10 seconds, during which 19.4 percent of a video’s audience defects.

This phenomenon, known as “viewer abandonment,” is of intense interest to those who make online videos or advertise alongside them. Visible Measures studied the abandonment rate of 40 million videos over seven billion viewings. Music videos had especially high rates of abandonment, as did videos slow to reach a punchline — for example, a Budweiser ad about a man humiliated while buying pornography, which loses nearly 40 percent of viewers in the first 10 seconds.

“It took a shocking 12 seconds to get to the conceit,” said Matt Cutler, the head of research at Visible Measures.