This article reports on a German study in which 2 groups of students were asked to fill out a questionnaire. The questionnaires were all on the same topics - simple stuff like opening a bank account - but the questions were phrased either concretely or abstractly. Turns out the students who were given the abstract questions procrastinated much more.
This is no surprise. As I write in my book, The Lifelong Activist, "vagueness opens the door for procrastination." Procrastination is a response to fear - fear of failure or success, usually - and it is a wily and insidious habit/reflex. It looks for the slightest uncertainty or doubt or ambivalence and feeds on it and amplifies it. Abstract instructions by their nature are less defined than concrete ones, and so if you're prone to procrastination they'll often catalyze it.
In your own life, think of projects you procrastinated on (or are doing so now) and ask yourself whether the instructions were clear and/or concrete. Ask whether you were given contradictory sets of instructions (e.g., "do this fast AND well"), or whether there was a conflict between this project and other areas of your life. Also, ask yourself whether you were given all the resources and support you needed to complete the job - if you weren't, that's another source of conflict.
Many, many cases of procrastination are caused by these "outside" factors.