The average attention spam during a lecture is from 10 to 20 minutes. After that period fatigue or boredom come to scene affecting the purpose of the speech. In order to keep focus, there should be a shift in the presentation approach. With Flipwit your audience can report when is reaching that level, so you can make a break to change the approach reducing fatigue and recovering their attention.

*Sousa, David A.. How the Brain Learns ( Kindle Position1268). SAGE Publications. Kindle Edition.