Learning before assessments: problems
Superficial learning
Summative assessments can have profound and negative influences on the learning beforehand. High-stakes assessments drive learners to adopt undesirable learning behaviours and "binge learning" shortly before tests. Francois Cilliers has performed a series of studies which look at this in more detail. He has shown that this problem occurs both in the early years of medical degrees and in the later clinical years. See here for more details.
Driving the wrong learning
High-stakes assessments are so important to learners that they will do what it takes to ensure that they pass. Unfortunately, this often means that they spend less time in the clinical workplace and more time revising with colleagues in an artificial context. Rudland and colleagues explain this worrying phenomenon in more detail in their intriguingly-named paper: "You can do it late at night or in the morning. You can do it at home. I did it with my flatmate." The educational impact of an OSCE. Worryingly, it also leads learners to ignore feedback they receive in the clinical workplace in the run up to an examination, as they perceive that it will harm their chances of paasing an OSCE. See here for more details.