Gary Wong, Consultant, Canada
James: Advances in the cognitive sciences have revealed numerous decision-making errors that humans are prone to make. Have a look at the ones posted on the 12manage Cognitive Bias page
What this means is that methods that reduce decision-making to scoring a rating system with weighted criteria are not as neutral and objective as one would think. The selecting of criteria and scores will be tainted with cognitive biases.
For example, if the first alternative you see is a good one, you will rate it 4 or 5 out of 5. All other alternatives should be scored independently but the mind will score them relative to the first one. This is called anchoring bias.