As academics we often assume that allocating marks to a task will influence student decision-making when it comes to completing that task. Marks are used by lecturers to indicate the relative importance of each of the criteria used for marking the assessment task and we expect the student to respond to the marks' allocation. This Postcard suggests that there may be a number of factors that play a role in student decision-making and that just allocating marks to an action or increasing the amount of instruction regarding the action may not mean that students will respond as we might expect.