The literal meaning of “ishiki-takai” is similar to ‘highly motivated’ or ‘highly conscious.’ The first use of “ishiki-takai” is to refer to these sorts of people. A master’s student in Todai said, “I would use ‘ishiki-takai’ to refer to a person who is job hunting like crazy or a master’s student who works on their research far more than the average student.” In this second use, the expression is used when the degree to which someone does something serious goes too far.
The expression can also be uttered towards someone who is showing off; just doing something considered to be hard in order to appear highly motivated. One student considers a person to be ishiki-takai when they talk about serious topics, such as their future or issues facing modern society at a drinking party. This kind of “ishiki-takai” can be replaced by the synonym word “ishiki-takai-kei (a “type” of ishiki-takai),” which has a much stronger negative nuance.
From: Kai Ohata blog entry