The Human Ov erview Human can b e view ed as an - PDF document

The Human Ov erview Human can b e view ed as an information pro cessing system, for example, Card, Moran and New ell's Mo del Human Pro cessor. A simple mo del: information receiv ed and resp onses giv en � via input{output c hannels information stored in memory � information pro cessed and applied in � v arious w a ys Capabiliti es of h umans in these areas are imp ortan t to design, as are individual di�erences. Human{Com puter In teraction, Pren tice Hall The Human (1) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Input{Output c hannels Vision Tw o stages in vision ph ysical reception of stim ulus � pro cessing and in terpretation of stim ulus � The ph ysical apparatus: the ey e mec hanism for receiving ligh t and � transforming it in to electrical energy ligh t re�ects from ob jects; their images are � fo cused upside-do wn on retina retina con tains ro ds for lo w ligh t vision and � cones for colour vision ganglion cells detect pattern and mo v emen t � Human{Com puter In teraction, Pren tice Hall The Human (2) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

In terpreting the signal Size and depth visual angle indicates ho w m uc h of �eld of � view ob ject o ccupies (relates to size and distance from ey e) visual acuit y is abilit y to p erceiv e �ne detail � (limited) familiar ob jects p erceiv ed as constan t size � in spite of c hanges in visual angle | la w of size constancy cues lik e o v erlapping help p erception of size � and depth Human{Com puter In teraction, Pren tice Hall The Human (3) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

In terpreting the signal (con t) Brigh tness sub jectiv e reaction to lev els of ligh t � a�ected b y luminance of ob ject � measured b y just noticeable di�erence � visual acuit y increases with luminance as � do es �ic k er Colour made up of h ue, in tensit y , saturation � cones sensitiv e to colour w a v elengths � blue acuit y is lo w est � 8% males and 1% females colour blind � Human{Com puter In teraction, Pren tice Hall The Human (4) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

In terpreting the signal (con t) The visual system comp ensates for mo v emen t and c hanges in luminance. Con text is used to resolv e am biguit y . Optical illusi ons sometimes o ccur due to o v er comp ensation. Human{Com puter In teraction, Pren tice Hall The Human (5) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Figure 1: The P onzo illusi on Figure 2: The Muller Ly er illusi on Human{Com puter In teraction, Pren tice Hall The Human (6) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Reading Sev eral stages: visual pattern p erceiv ed � deco ded using in ternal represen tation of � language in terpreted using kno wledge of syn tax, � seman tics, pragmatics Reading in v olv es saccades and �xations. P erception o ccurs during latter. W ord shap e is imp ortan t to recognition. Negativ e con trast impro v es reading from computer screen. Human{Com puter In teraction, Pren tice Hall The Human (7) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Hearing Pro vides information ab out en vironmen t: distances, directions, ob jects etc. Ph ysical apparatus: outer ear | protects inner and ampli�es � sound middle ear | transmits sound w a v es as � vibrations to inner ear inner ear | c hemical transmitters are � released and cause impulses in auditory nerv e Sound pitc h | sound frequency � loudness | amplitude � tim bre | t yp e or qualit y � Human{Com puter In teraction, Pren tice Hall The Human (8) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Hearing (con t) Humans can hear frequencies from 20Hz to 15kHz | less accurate distinguishi ng high frequencies than lo w. Auditory system �lters sounds | can attend to sounds o v er bac kground noise. F or example, the co c ktail part y phenomenon. Human{Com puter In teraction, Pren tice Hall The Human (9) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

T ouc h Pro vides imp ortan t feedbac k ab out en vironmen t. Ma y b e k ey sense for someone who is visually impaired. Stim ulus receiv ed via receptors in the skin: thermoreceptors | heat and cold � no ciceptors | pain � mec hanoreceptors | pressure (some � instan t, some con tin uous) Some areas more sensitiv e than others e.g. �ngers. Kinethesis | a w areness of b o dy p osition a�ecting comfort and p erformance. Human{Com puter In teraction, Pren tice Hall The Human (10) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Mo v emen t Time tak en to resp ond to stim ulus: reaction time + mo v emen t time Mo v emen t time | dep enden t on age, �tness etc. Reaction time | dep enden t on stim ulus t yp e: visual | 200ms � auditory | 150 ms � pain | 700ms � Increasing reaction time decreases accuracy in the unskilled op erator but not in the skilled op erator. Human{Com puter In teraction, Pren tice Hall The Human (11) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Mo v emen t (con t) Fitts' La w describ es the time tak en to hit a screen target: M t = a + b l og ( D =S + 1) 2 where a and b are empirically determined constan ts, M t is mo v emen t time, D is Distance and S is Size. T argets in general should b e large as p ossible and the distances as small as p ossible. Human{Com puter In teraction, Pren tice Hall The Human (12) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Memory There are three t yp es of memory function. Sensory memories Short-term memory Rehearsal Attention Long-term memory Iconic or Echoic Working memory Haptic Sensory memory Bu�ers for stim uli iconic | visual stim uli � ec hoic | aural stim uli � haptic | touc h stim uli � Constan tly o v erwritten. Information passes from sensory to STM b y atten tion. Selection of stim uli go v erned b y lev el of arousal. Human{Com puter In teraction, Pren tice Hall The Human (13) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Short-term memory (STM) Scratc h-pad for temp orary recall rapid access | 70ms � rapid deca y | 200ms � limited capacit y | 7 + = 2 digits or � � c h unks of information Recency e�ect | recall of most recen tly seen things b etter than recall of earlier items. Some evidence for sev eral elemen ts of STM | articulatory c hannel, visual c hannel etc. | in terference on di�eren t c hannel do es not impair recall. Human{Com puter In teraction, Pren tice Hall The Human (14) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Long-term memory (L TM) Rep ository for all our kno wledge slo w access | 1/10 second � slo w deca y , if an y � h uge or unlimited capacit y � Tw o t yp es episo dic | serial memory of ev en ts � seman tic | structured memory of facts, � concepts, skills Information in seman tic L TM deriv ed from episo dic L TM. Human{Com puter In teraction, Pren tice Hall The Human (15) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1

Long-term memory (con t.) Seman tic memory structure pro vides access to information � represen ts relationships b et w een bits of � information supp orts inference � Mo del: seman tic net w ork inheritance | c hild no des inherit prop erties � of paren t no des relationships b et w een bits of information � explicit supp orts inference through inheritance � Human{Com puter In teraction, Pren tice Hall The Human (16) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 1