The extremely clever Malcolm Gladwell did consular officers an inadvertent favor with his best-selling book "Blink" which extolled but also warned about high stakes, instant decision making. His "New Yorker" article "The New-Boy Network," anthologized in the 2009 book "What the Dog Saw," goes a bit further to second guess such decision-making, and is worth a look by anyone required to make major decisions based on personal interviews. Such as consular officers.
Gladwell starts by describing studies that show how a first impression - created by nothing more than a smile and handshake - appears to hold up through the course of a long personal interview. But then he looks again, with the help of further studies, and writes, "That people who simply see the handshake arrive at the same conclusions as people who conduct a full interview also implies, perhaps, that those initial impressions matter too much - that they color all the other impressions that we gather over time."
Fundamental attribution error - the tendency to understand behavior as a function of personality and character rather than situation - and confirmation bias - the tendency to search for or interpret information in a way that confirms our preconceptions - can act together to cause us to make faulty decisions, especially in visa interviews. The solution is not, however, longer interviews; we simply use those - unconsciously but faithfully - to further harden that first impression. The solution is better questions.