The Internet is having a profound impact on physicians' medical decision making. 
One recent survey of 277 physicians showed that 72% of physicians regularly used 
the Internet to research medical information and 51% admitted that information 
from web sites influenced their clinical decisions. This paper describes the 
first cognitive evaluation of four state-of-the-art Internet search engines: 
Google (i.e., Google and Scholar.Google), MedQA, Onelook, and PubMed for 
answering definitional questions (i.e., questions with the format of "What is 
X?") posed by physicians. Onelook is a portal for online definitions, and MedQA 
is a question answering system that automatically generates short texts to 
answer specific biomedical questions. Our evaluation criteria include quality of 
answer, ease of use, time spent, and number of actions taken. Our results show 
that MedQA outperforms Onelook and PubMed in most of the criteria, and that 
MedQA surpasses Google in time spent and number of actions, two important 
efficiency criteria. Our results show that Google is the best system for quality 
of answer and ease of use. We conclude that Google is an effective search engine 
for medical definitions, and that MedQA exceeds the other search engines in that 
it provides users direct answers to their questions; while the users of the 
other search engines have to visit several sites before finding all of the 
pertinent information.