Glossary - Foundations for Designing User-Centered Systems - page 416

Sharp end The part of the system where the user interacts with the technology.
Sometimes used in contrast to the blunt end.

Short term memory (STM) A relatively limited capacity store for items that
have received a limited amount of processing or interpretation. STM is

somewhat analogous to the registers in a computer.

Signal detection theory (SDT) A mathematical theory of the detection of
physical signals based on the assumption that sensitivity to a signal depends on
its intensity, the amount of noise, the user's motivation, and the criterion set for
registering responses to the signal. Sometimes referred to as the Theory of
Signal Detection (TSD).

Slip A failure in the execution of an action. Refers to performing the wrong action
in the right circumstances.

Social capital A concept that highlights the value of social relations and the role
of cooperation and confidence in establishing trusts and norms to get collective
results.

Socio-technical systems Systems that involve a complex interaction between
humans, machines, and the environmental aspects of the work system. (Now-
adays this description applies to most enterprise systems.)

Soft systems methodology Essentially an analytical approach, mostly focusing
on organizational aspects of the system. It does not purport to support systems
design.

Spiral model A model of the system development lifecycle, which uses an iter-
ative development process.

S-R (Stimulus-response) compatibility Refers to the fact the response should be
compatible with the stimulus that causes it. This is typically exploited in the
way that physical aspects of an interface (e.g., buttons) and displays (e.g.,
GUIs) are mapped onto the world that they are representing. It also explains
why the call buttons for elevators are situated with the ''up'' button above the
''down'' one.

Stimulus-response mapping The mapping between the stimulus that the users
see to the responses that they produce. Mappings that are simple and similar to
previous mappings lead to faster, less error-prone interactions.

Subitizing The ability to determine directly the number of objects the user is
looking at without counting them. This only works for small numbers of
objects.

Summative evaluation A type of evaluation used to assess the success of the
finished system or product, summarizing its overall impact and effectiveness.