Cognition: Memory, Attention, and Learning - Foundations for Designing User-Centered Systems - page 130

much by the way memory retrieval supports decision making as by how the
choices themselves are made. The inherent biases associated with memory can
often affect how well it operates.
5.2.4.1 Interference
The retrieval of items from memory can either be hindered or helped by other
items in memory. If two items are very similar they can be confused for one other.
For example, if you spend a long time knowing someone's name incorrectly, or
you type in a command incorrectly a few times, it can take much longer to correct
this error. This type of interference has been proposed as one of the primary
aspects that makes learning arithmetic difficult (Siegler 1988 ). The intelligent
tutoring systems based on ACT-R, therefore, do not allow the user to practice
incorrect knowledge (Anderson et al. 1989 ). This is likely to be one of the ways
that they can help students learn the same material in one-third of the typical time
(Corbett and Anderson 1990 ). Interface designers should thus be mindful of errors
and how interfaces help users to not remember them!
5.2.4.2 Retrieval Biases
Items presented towards the beginning of a sequence (primacy) or towards the end
of a sequence (recency) are more successfully retrieved from memory. When it
comes to reasoning about a situation or a set of activities, the items retrieved to
support reasoning will be biased in those two directions. The use of an external
memory aid and formal analysis can help.
The von Restorff effect will also apply. Information that is stored in a context
that is distinctive will be easier to retrieve. The relative amounts or numbers of
items retrieved will thus not support appropriate reasoning, as the items will not be
retrieved in proportion to their occurrence in the world.
5.2.4.3 Encoding Effects
The content of an item that is to be stored in memory can be influenced by its
encoding. The location of the item, the location of the user, sights, smells, sounds,
and mental state can all be included in the way the item is encoded for storage.
Examples of this include certain smells bringing back childhood memories, and
certain people only recognized well in certain contexts. For example, we find it
much harder to recognize students outside the classroom environment in which we
met them.
Users will have these same effects. The information that they can retrieve for
computer systems may in some cases be tied to aspects of the interface that you did
not intend or may not even have control over. The particular terminal or computer