Perception Lecture, IE 486, Fall 2024 PDF

IE 486 – Fall 2024 Portions of these notes were taken from N. Sarter (2012). UM IOE 434 Lecture Notes.  “Viewed as a geometric figure, the ant’s path is irregular, complex, hard to describe. But it’s complexity is really a complexity in the surface of the beach, not complexity in the ant” – Si...

IE 486 – Fall 2024 Portions of these notes were taken from N. Sarter (2012). UM IOE 434 Lecture Notes.  “Viewed as a geometric figure, the ant’s path is irregular, complex, hard to describe. But it’s complexity is really a complexity in the surface of the beach, not complexity in the ant” – Simon (1981)  Implications: to understand behavior, we need descriptions of the “landscape” in which behavior takes place and of the psychological mechanisms that are generating the behavior “Whilst part of what we perceive comes through our senses from the object before us, another part (and it may be the larger part) always comes out of our head.” – William James, 1890  Things are affected by where they are and by what surrounds them… so that things are better described as “more than the sum of their parts”  Gestaltists believed that context was very important in perception  Things which are closer together will be seen as belonging together  Things which share visual characteristics such as shape, size, color, texture, value, or orientation will be seen as belonging together  We tend to see complete figures even when part of the information is missing  The whole of a figure is perceived rather than the individual parts which make up the figure  We tend to perceive elements moving in the same direction as being more related than elements that are stationary or that more in different directions  People are surprisingly poor at noticing large changes to objects and motion pictures when these changes happen at the same time as a visual transient, such as an eye movement or flash of a display (Simon, 2000)  Observers attending to a particular object or event often fail to report the presence of an unexpected and therefore unattended items  Color can be a powerful tool to improve user interfaces, but its inappropriate use can severely reduce the performance of the systems we build  Provides objective and quantitative evidence of a user’s visual processes  Helps to reveal what a person is looking at  Eye-mind hypothesis:  What a person is interested in  What grabbed a person’s attention  Three broad types/techniques:  Electro-oculography (EOG)  Measures electrical potential difference  Scleral contact lens/search coil  Measures wire coil’s orientation in a magnetic field  Video-based  Camera used to take video of the eye  Can be desktop-mounted or head- mounted  Most commonly used  Camera image is used to measure distinguishable properties of the eye  Pupil shape  Corneal reflection  For pupil and corneal reflection, light source needed (infrared light) – indicates where person is looking  Head-tracking can be used to account for the movement of the head  Eye calibration needed in order to accurately map screen locations to eye tracker coordinates  Fixations: spatially stable gazes during which visual processing occurs; characterized by location and duration (~ 100-300 msecs)  Saccades: rapid eye movements between successive fixations  Scanpath: sequence of fixations and saccades  Area of interest: regions of the display on which analysis is conducted, generally defined by the experimenter 2 1 3  Gaze (or dwell): series of fixations within a particular Area of Interest (AOI), beginning with the first fixation on that AOI and ending with the last fixation inside of that AOI  Fixations and saccades form the building blocks for numerous other eye tracking metrics  For example: Metric Usually related to Time to first fixation on Target salience target Scanpath length Search efficiency Convex hull area Layout/organization Fixation duration Interest in target  Caution: metrics might mean different things  Long fixation duration: interest or uncertainty/confusion?  Fixation plot  Fixations and saccades  Sequence information  Heat map  Aggregated fixations  No sequence information  Cannot track peripheral visual (lose about 98% of visual field)  Debate about eye-mind hypothesis  Shows where and not why  Eye tracker type could bias results  Websites  Software  Cockpits  Car dashboards  Maps  Cellphones (Samsung Galaxy) …