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Human information processing Perception Motor skills Memory Decision making Attention


  1. �������������� � Human information processing � Perception � Motor skills ����������������������������� � Memory � Decision making � Attention � Vision Fall 2004 6.831 UI Design and Implementation 1 Fall 2004 6.831 UI Design and Implementation 2 ���������������������������� �������� Attention ���������� ������� ��������� ������� ������ ����� ������ ������ ���������� ���������� ��������� ����� ������� ������ ��������� ��������� ��������� ����� � Memory properties � Encoding: type of things stored ��������� ������� ������� � Size: number of things stored ������ ������ � Decay time: how long memory lasts �������� Fall 2004 6.831 UI Design and Implementation 3 Fall 2004 6.831 UI Design and Implementation 4 1

  2. ����� ������������������ ���������� � Processors have a cycle time � Visual information store � T p ~ 100ms [50-200 ms] � encoded as physical image � T c ~ 70ms [30-100 ms] � size ~ 17 [7-17] letters � T m ~ 70ms [25-170 ms] � decay ~ 200 ms [70-1000 ms] � Auditory information store ���������� ��������� ����� � encoded as physical sound ��������� ��������� ��������� � size ~ 5 [4.4-6.2] letters � Fastman may be 10x faster than � decay ~ 1500 ms [900-3500 ms] Slowman Fall 2004 6.831 UI Design and Implementation 5 Fall 2004 6.831 UI Design and Implementation 6 "����� ���#�$���� %�&������������ �����������!����� � Two stimuli within the same PP cycle � Bottom-up uses features of stimulus (T p ~ 100ms) appear fused � Top-down uses context � Consequences � temporal, spatial � 1/ T p frames/sec is enough to perceive a � draws on long-term memory moving picture (10 fps OK, 20 fps smooth) � Computer response < T p feels instantaneous � Causality is strongly influenced by fusion Fall 2004 6.831 UI Design and Implementation 7 Fall 2004 6.831 UI Design and Implementation 8 2

  3. ����'��� (����������������������� � � Chunk � : unit of perception or memory � Spotlight metaphor � Spotlight moves serially from one input � Chunking depends on presentation and channel to another what you already know � Visual dominance : easier to attend to B M W R C A A O L I B M F B I visual channels than auditory channels MWR CAA OLI BMF BIB � All stimuli within spotlighted channel are BMW RCA AOL IBM FBI processed in parallel � 3-4 digit chunking is ideal for encoding � Whether you want to or not unrelated digits Fall 2004 6.831 UI Design and Implementation 9 Fall 2004 6.831 UI Design and Implementation 10 ������������������������)�����(���� *�&�%�����(���� Book Green Pencil Orange Slide Red Window Black Car Pink Hat Blue Fall 2004 6.831 UI Design and Implementation 11 Fall 2004 6.831 UI Design and Implementation 12 3

  4. �������#������������ ���' ��������&�����������+������������ � Cognitive processor � Reaction time depends on information � compares stimuli content of stimulus � selects a response � Types of decision making RT = c + d log 2 1/Pr(stimulus) � Skill-based � e.g., for N equiprobable stimuli, each � Rule-based requiring a different response: � Knowledge-based RT = c + d log 2 N Fall 2004 6.831 UI Design and Implementation 13 Fall 2004 6.831 UI Design and Implementation 14 ����� (���������������� %�#�����(���������,��������'���- � Accuracy varies with reaction time � Resource metaphor � Attention is a resource that can be divided among � Can choose any point on curve different tasks simultaneously � Can move curve with practice � Multitasking performance depends on: � Task structure � Modality: visual vs. auditory log(P(correct)/P(error)) � Encoding: spatial vs. verbal moves up with practice � Component: perceptual/cognitive vs. motor vs. WM � Difficulty � Easy or well-practiced tasks are easier to share Reaction time Fall 2004 6.831 UI Design and Implementation 15 Fall 2004 6.831 UI Design and Implementation 16 4

  5. ���������������� !������ ��& � Open-loop control � Fitt � s Law � Motor processor runs a program by itself � Time T to move your hand to a target of � cycle time is T m ~ 70 ms size S at distance D away is: � Closed-loop control T = RT + MT = a + b log (2D/S) � Muscle movements (or their effect on the world) D are perceived and compared with desired result � cycle time is T p + T c + T m ~ 240 ms S � Depends only on index of difficulty log(2D/S) Fall 2004 6.831 UI Design and Implementation 17 Fall 2004 6.831 UI Design and Implementation 18 ./�������������!������ ��& ����������������!������ ��& � Moving your hand to a target is closed- - Targets at screen edge are easy to hit loop control - Mac menubar beats Windows menubar � Each cycle covers remaining distance D - Unclickable margins are foolish with error � D - Hierarchical menus are hard to hit - Gimp/GTK: instantly closes menu Velocity Position - Windows: .5 s timeout destroys causality - Mac does it right: triangular zone - Linear popup menus vs. pie menus Time Time Fall 2004 6.831 UI Design and Implementation 19 Fall 2004 6.831 UI Design and Implementation 20 5

  6. ��&�����&������������ )��'�����������,)�- � Time T n to do a task the n th time is: � Small capacity: 7 ± 2 � chunks � T n = T 1 n � � � Fast decay (7 [5-226] sec) � Maintenance rehearsal fends off decay � Interference causes faster decay � is typically 0.2-0.6 Fall 2004 6.831 UI Design and Implementation 21 Fall 2004 6.831 UI Design and Implementation 22 ���� ������������,���- ����.�� � Huge capacity � Little decay � Elaborative rehearsal moves chunks from WM to LTM by making connections with other chunks Fall 2004 6.831 UI Design and Implementation 23 Fall 2004 6.831 UI Design and Implementation 24 6

  7. �������������� ��������������������������� � Rods � Brightness � Only one kind (peak response in green wavelengths) M + L + rods � Sensitive to low light ( � scotopic vision � ) � Multiple nearby rods aggregated into a single nerve signal � Red-green difference � Saturated at moderate light intensity ( � photopic vision � ) � Cones do most of the vision under photopic conditions L - M � Cones � Blue-yellow difference � Operate in brighter light � Three kinds: S(hort), M(edium), L(ong) weighted sum of S, M, L � 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 25 Fall 2004 6.831 UI Design and Implementation 26 ������"�������� ����������(��������� � Red-green color blindness (protonopia & � Different wavelengths focus differently deuteranopia) � Highly separated wavelengths (red & blue) � 8% of males can � t be focused simultaneously � 0.4% of females � Guideline: don � t use red-on-blue text � Blue-yellow color blindness (tritanopia) � It looks fuzzy and hurts to read � Far more rare � Guideline: don � t depend solely on color distinctions � use redundant signals: brightness, location, shape Fall 2004 6.831 UI Design and Implementation 27 Fall 2004 6.831 UI Design and Implementation 28 7

  8. "����%�������(�����������+����#� !�#�������*��+��� � Fovea has no S cones � Rods are more sensitive to dim light � Can � t resolve small blue features (unless they � In scotopic conditions, peripheral vision have high contrast with background) � Lens and aqueous humor turn yellow with (rod-rich) is better than foveal vision age � Easier to see a dim star if you don � t look � Blue wavelengths are filtered out directly at it � 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 29 Fall 2004 6.831 UI Design and Implementation 30 8

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