The basic idea is that it isn't really increasing your cognitive abilities. It is increasing your access to abilities that are taking place all the time. The fact is that, as a matter of survival, we filter out a great deal of what we observe. Also, as we go through school, we begin to filter out many of the ongoing messages from our inner mind. Image streaming seeks to return to us a skill that we have been continuously losing and de-emphasizing as we get older.
Books like "The User Illusion" show evidence that suggests that our conscious awareness is a sliver of what is really going on in our brains. Much more is being noticed/processed than we are prepared to consciously deal with. In fact, this book deals with evidence that actions we take physically begin less than a second before we're aware of making the decision to act. The evidence suggests that what we observe as reality is an illusion created by our inner mind to keep us functional and protect us from a level of information intake/processing that we just cannot handle at a conscious level. (I know, creepy shades of "The Matrix.")
You have an incredible tool at your disposal. Chances are quite good that you are not using it to its real level of capability. Win Wenger suggests that, over time, you have developed an internal editor that takes on the role of deciding what you think/notice/act upon. This course seeks to help you dampen the impact of that editor so you can decide for yourself what you respond to.
You can decide this for yourself by doing some image streaming before getting out your credit card. There are many sites that describe the process, including www.winwenger.com. Do it for a while and see for yourself whether or not you notice an improvement in the way you deal with information. Just make sure that you follow the guidelines that are set down. Attempts to short-cut the process will weaken or impede your results.
This isn't meant as a sales letter for the course or for Dr. Wenger's concepts. The course (so far--through tape 5) effectively translates Dr. Wenger's and Paul Scheele's concepts into a useful format. That doesn't mean that the course would be good for you. Play around with the concepts first and notice your results.