Glossary - Foundations for Designing User-Centered Systems - page 414

Operators Generally used to refer to users who work in industrial settings such as
nuclear power stations and chemical plants.
Parafovea The area of the retina that immediately surrounds the fovea. It pro-
vides a lower level of visual acuity than the fovea.
Periphery The area of the retina beyond the parafovea. Visual acuity is at its
lowest in the periphery and vision is only in black and white.
Pop-out (effect) Refers to the effect that some stimuli appear to 'pop out' of a
visual field based on color, size, shape, or other unique and easy to distinguish
features.
Post-completion errors Errors that arise when the main goal for a task has been
accomplished, but the goals of the subtasks have not.
Power law of learning A mathematical description of how learning takes place
over time. Usually represented by an equation of the form RT = aP -b ? c,
where RT is the response time for a particular trial, P, and a, b, and c are all
constants.
PQ4R A method of studying designed to help readers retain more from what they
read. It stands for Preview, Question, Read, Reflect, Recite, Review.
Premature commitment One of the cognitive dimensions. It relates to the situ-
ation where design decisions have to be made before all of the required
information is available.
Primacy effect Refers to the fact that the items presented at the start of a list of
items to be learned are subsequently better recalled than items in the middle of
the list in a free (unprimed) recall situation.
Priming Used with respect to learning to refer to the presentation of a particular
experience which makes the responder more sensitive or responsive to a wide
range of stimuli.Used with respect to memory to refer to the triggering of the
recall of related items, e.g., ''yellow'' would prime the recall of ''banana,''
''custard,'' and other items that are yellow in color.
Problem solving Problem solving essentially involves working out how to get
from the current state of affairs to the goal that you are trying to achieve by
taking appropriate actions. More formally, this can be described as applying
operators to states to reach a goal.
Procedural memory A hypothesized store which holds procedures that encap-
sulate how to do a particular task, such as how to move a knight in chess.
Programmable user models (PUMs) A psychologically constrained architecture
which an interface designer programs to simulate a user performing a range of
tasks with a proposed interface.