A virtual reality? Human perceptual function

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14 Νοε 2013 (πριν από 3 χρόνια και 1 μήνα)

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A virtual reality? Human
perceptual function

R.Fielding

Community Medicine & BSU

HKU

Lecture outline


Learning objectives


Sensation versus perception


Features of perception


Stimulus characteristics


organizational aspects


Hypothesis testing


Depth perception & cues


Perceptual development



Learning objectives


differentiate between sensation
and perception.


describe key functional features of
human perceptual system.


list stimulus characteristics
commanding attention and
describe organizational aspects of
stimulus processing.




define and give reasons for
importance of illusions and
hypotheses
-
testing features of
perception.


give examples of visual cues in
depth perception.


Describe the main stages of
perceptual development.


Sensation vs. perception


Sensation


Sense organs are energy
detectors and signalling devices,
which give rise to


afferent neural activity.


afferent activity presents centrally
primarily as sensation.


Perceptions :


are synthetic central processes
involving the attribution of
meaning to extrinsic and intrinsic
activity.


are rule bound hypotheses
applied to anticipated stimuli.


have “bottom
-
up” and “top
-
down” features.



Functional features


Recognition


Attentional

processes


Limited capacity channels


Bottom
-
up processing (input
driven e.g. detection of specific
elements and assembly into
complex forms e.g. geons*).



Top
-
down processing
(knowledge driven, e.g.
contexts and expectations)


Constancies


Synthesis


Top
-
down processing


Hypothesis
-
testing


Stimulus characteristics


Size, colour, shape, location,
pitch, timbre.


intensity (brightness/volume)


magnitude (size)


contrast


novelty


salience (relevance)


Organizational aspects


Stimuli are provisionally
organized (pre
-
attentively)
according to bottom
-
up
processes


feature analysis; proximity;
organization; similarity;
simplicity; continuity.


Hypothesis testing



Figure
-
ground


perceptual patterning


illusions

These illustrate the dynamic nature of
perception
-

i.e. perception is not just
passive reception of sensation but
an active process of constructed
experience based on hypotheses

Depth perception and cues


Monocular cues


interposition; relative size;
height in plane; linear
perspective; texture gradient;
light and shadow.


Binocular cues


parallax; ocular convergence



Perceptual development


Is perception innate or learned?


Birth: visual acuity low: vision directed
at contrast boundaries.


by 3/12 facial expression detectable.


by 6/12 acuity good, 1
-
5 years =adult.


~6/12 constancies and self/non
-
self


Critical periods for visual
development



Perceptual
-
motor (p
-
m)
coordination intimately linked to
stimulation and active interaction
with environment.


New p
-
m learning rapid even in
adulthood if
self
-
generated

activity
allowed, but not if inactive.


Relevance to medical care


Perceptions of threat, vulnerability, risk


Perceptions of patients by doctors and or
doctors by patients


Preparation for medical procedures


Pain and pain control, neurological topics


Diagnostic skill and error


Paediatrics, geriatrics, intensive care


Examinations


and every other aspect of medical
practice...


Further information


Atkinson RL, et al. (1993)
Introduction to
Psychology

(11th Edn.) Ch.5, p. 164
-
201.
or


Weiten W. (1992)
Psychology: Themes and
variations
. Ch 4. 107
-
151.


Weinman J. (1997) An outline of psychology
as applied to medicine. Ch 2.


Http://www.bhs.mq.edu.au/psy/105/lectures


Lectures on Feature Detector and visual
illusions & constancies.