������������������������� ����������������������������� Fall 2004 6.831 UI Design and Implementation 1 Fall 2004 6.831 UI Design and Implementation 2 ������������� ���������������������� Fall 2004 6.831 UI Design and Implementation 3 Fall 2004 6.831 UI Design and Implementation 4 1
������������������ ��������! �������������� Attention � Human information processing � Perception ���������� � Motor skills ���������� ��������� ����� ������� ������ ��������� ��������� ��������� ����� � Memory � Decision making � Attention ��������� ������� ������� ������ ������ � Vision �������� Fall 2004 6.831 UI Design and Implementation 5 Fall 2004 6.831 UI Design and Implementation 6 "������� �����#������������������ ���������� � Visual information store ������� ��������� ������� ������ � encoded as physical image ����� ������ ������ � size ~ 17 [7-17] letters � decay ~ 200 ms [70-1000 ms] � Memory properties � Auditory information store � Encoding: type of things stored � encoded as physical sound � Size: number of things stored � size ~ 5 [4.4-6.2] letters � Decay time: how long memory lasts � decay ~ 1500 ms [900-3500 ms] Fall 2004 6.831 UI Design and Implementation 7 Fall 2004 6.831 UI Design and Implementation 8 2
��������� ���������������� � Processors have a cycle time � Two stimuli within the same PP cycle � T p ~ 100ms [50-200 ms] (T p ~ 100ms) appear fused � T c ~ 70ms [30-100 ms] � Consequences � T m ~ 70ms [25-170 ms] � 1/ T p frames/sec is enough to perceive a moving picture (10 fps OK, 20 fps smooth) ���������� ��������� ����� � Computer response < T p feels ��������� ��������� ��������� instantaneous � Fastman may be 10x faster than � Causality is strongly influenced by fusion Slowman Fall 2004 6.831 UI Design and Implementation 9 Fall 2004 6.831 UI Design and Implementation 10 $�����#���%�&����#'�(�� ��������� ����)��! � Bottom-up uses features of stimulus � � Chunk � : unit of perception or memory � Top-down uses context � Chunking depends on presentation and � temporal, spatial what you already know � draws on long-term memory B M W R C A A O L I B M F B I MWR CAA OLI BMF BIB BMW RCA AOL IBM FBI � 3-4 digit chunking is ideal for encoding unrelated digits Fall 2004 6.831 UI Design and Implementation 11 Fall 2004 6.831 UI Design and Implementation 12 3
*������������� ��������� ������������������������+�����*���� � Spotlight metaphor Book � Spotlight moves serially from one input Pencil channel to another Slide � Visual dominance : easier to attend to visual channels than auditory channels Window � All stimuli within spotlighted channel are Car processed in parallel � Whether you want to or not Hat Fall 2004 6.831 UI Design and Implementation 13 Fall 2004 6.831 UI Design and Implementation 14 ��!����%�� ��������! ,�(�'�����*!��� � Cognitive processor Green � compares stimuli Orange � selects a response Red � Types of decision making Black � Skill-based � Rule-based Pink � Knowledge-based Blue Fall 2004 6.831 UI Design and Implementation 15 Fall 2004 6.831 UI Design and Implementation 16 4
�����#*���������������� ���)#��������(�����������-������������ � Reaction time depends on information � Accuracy varies with reaction time � Can choose any point on curve content of stimulus � Can move curve with practice RT = c + d log 2 1/Pr(stimulus) log(P(correct)/P(error)) � e.g., for N equiprobable stimuli, each moves up with practice requiring a different response: RT = c + d log 2 N Reaction time Fall 2004 6.831 UI Design and Implementation 17 Fall 2004 6.831 UI Design and Implementation 18 '�%�����*���������."�������)��!/ "����� ��������! � Resource metaphor � Open-loop control � Attention is a resource that can be divided among � Motor processor runs a program by itself different tasks simultaneously � cycle time is T m ~ 70 ms � Multitasking performance depends on: � Closed-loop control � Task structure � Muscle movements (or their effect on the world) � Modality: visual vs. auditory are perceived and compared with desired result � Encoding: spatial vs. verbal � cycle time is T p + T c + T m ~ 240 ms � Component: perceptual/cognitive vs. motor vs. WM � Difficulty � Easy or well-practiced tasks are easier to share Fall 2004 6.831 UI Design and Implementation 19 Fall 2004 6.831 UI Design and Implementation 20 5
01�������������������� ��( ������� ��( � Fitt � s Law � Moving your hand to a target is closed- � Time T to move your hand to a target of loop control � Each cycle covers remaining distance D size S at distance D away is: T = RT + MT = a + b log (2D/S) with error � D D Velocity Position S � Depends only on index of difficulty log(2D/S) Time Time Fall 2004 6.831 UI Design and Implementation 21 Fall 2004 6.831 UI Design and Implementation 22 ����������������������� ��( �(�����(���� ������� � Time T n to do a task the n th time is: - Targets at screen edge are easy to hit T n = T 1 n � � - Mac menubar beats Windows menubar - Unclickable margins are foolish - Hierarchical menus are hard to hit � is typically 0.2-0.6 - Gimp/GTK: instantly closes menu - Windows: .5 s timeout destroys causality - Mac does it right: triangular zone - Linear popup menus vs. pie menus Fall 2004 6.831 UI Design and Implementation 23 Fall 2004 6.831 UI Design and Implementation 24 6
+��)��!�"������.+"/ ���!#�����"������.��"/ � Small capacity: 7 ± 2 � chunks � � Huge capacity � Fast decay (7 [5-226] sec) � Little decay � Maintenance rehearsal fends off decay � Elaborative rehearsal moves chunks � Interference causes faster decay from WM to LTM by making connections with other chunks Fall 2004 6.831 UI Design and Implementation 25 Fall 2004 6.831 UI Design and Implementation 26 ����0�� ������������� � Rods � Only one kind (peak response in green wavelengths) � Sensitive to low light ( � scotopic vision � ) � Multiple nearby rods aggregated into a single nerve signal � Saturated at moderate light intensity ( � photopic vision � ) � Cones do most of the vision under photopic conditions � Cones � Operate in brighter light � Three kinds: S(hort), M(edium), L(ong) � S cones are very weak, centered in blue wavelengths � M and L cones are more powerful, overlapping � M centered in green, L in yellow (but called � red � ) Fall 2004 6.831 UI Design and Implementation 27 Fall 2004 6.831 UI Design and Implementation 28 7
��!���������� ������������� ������$�������� � Brightness � Red-green color blindness (protonopia & deuteranopia) M + L + rods � 8% of males � Red-green difference � 0.4% of females L - M � Blue-yellow color blindness (tritanopia) � Blue-yellow difference � Far more rare � Guideline: don � t depend solely on color weighted sum of S, M, L distinctions � use redundant signals: brightness, location, shape Fall 2004 6.831 UI Design and Implementation 29 Fall 2004 6.831 UI Design and Implementation 30 $����'�������*�����������-����%� ����������*��������� � Fovea has no S cones � Different wavelengths focus differently � Can � t resolve small blue features (unless they � Highly separated wavelengths (red & blue) have high contrast with background) can � t be focused simultaneously � Lens and aqueous humor turn yellow with � Guideline: don � t use red-on-blue text age � Blue wavelengths are filtered out � It looks fuzzy and hurts to read � Lens weakens with age � Blue is harder to focus � Guideline: don � t use blue against dark backgrounds where small details matter (text!) Fall 2004 6.831 UI Design and Implementation 31 Fall 2004 6.831 UI Design and Implementation 32 8
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