G-ScalE Psychophysics for Interface Avoiding Scalure
Issues in Scaling Research• The use of objects and icons are memory-based.• We can test and use principles of photo-object identification, such as shading, edge detection, etc.• However, we may be better off using trigrams text-type features, as these are more complex and recruit the same features as icon and image processing without the reliance on prior knowledge.
Visual Mechanisms• Contrast Coding – Contrast refers to luminance differences between the target and the background rather than overall luminance levels. – Contrast Signals and are extracted from retinal signals for visual encoding.• Size Coding • Size refers to a target’s angular size, proportional to retinal image size. • Target size is an important variable
Reading Acuity Charts • Reading Acuity: • The smallest print that a person can read without making significant errors.• Critical Print Size: • The smallest print that an individual can read with maximum speed.
Angular character size:– The corresponding visual angle subtended at the observer’s eye, and depends upon the physical size and the viewing distance. • Angular size in degrees = 57.3 x angular size in radians – (57.3 x physical size/viewing distance) – Measured in angular degrees or minutes of arc
40 cm 12/60° E 12 min arcCritical Print Size (CPS)Range = 0.15° to 0.3°Across studies, consensus for normally sighted readers = 0.2° (12 min-arc)Huey (1908/1968 X-height 1.5 mm, character size 2°, reading distance of 40cm
I min arc 12/60° E 12 min arc 40 cmCritical Print Size (CPS)• This angle is also used to specify visual acuity. It is called the minimum angle of resolution (MAR) and can also be given in log10 form, abbreviated as logMAR.• Snellan letters are constructed so that the size of the critical detail (stroke width and gap width) subtends 1/5th of the overall height.• Visual acuity (VA) in Snellen is given by the relation: VA = D’D
VA = D’/DVisual AcuityTarget resolution thresholds are usually expressed as the smallest angular sizeat which subjects can discriminate the separation between critical elements ofa stimulus pattern such as a pair of dots, a grating or a checkerboard
Visual SpanA key consideration for thearrangement of text may be theinclusion of visual span into designconsiderations. The Visual Span wasconstructed using trigrams, a non-textobject for letter recognition. It isconstructed of random strings of 3letters. 3 letters are used because thisrepresents a key feature of text:letters are flanked on both sides.human readers have a visual span of 7-11 letters. Fine and Rubin (1999)for high-contrast 1° letters the visualspan is 10.6 letters. Legge, Ahn, Klitz,and Luebker (1997a)
Understand Visual Processing The visual system is a complex network of modules and pathways, allspecializing in different tasks to contribute to our eventual impression of the world
Take home• Reification, multistability, and invariance are not necessarily separable modules to be modeled individually, but they could be different aspects of a single unified dynamic mechanism.• We are pattern recognition machines.
Memory in Perception• Experience in the world leads to memory.• As we interact with objects, we identify causation, concept, and variation.• This is useful for prediction and planning.• Common design features utilize this, often described as skeuomorphism:
Prior Knowledge• When we describe memory in image identification, we are often referring to the process called working memory.• Working memory success is based upon recency, frequency, and congruence.