Pre-attentive, Early Stage Perceptual Organization & Rhino 6’s Desktop Interface
Human Factors in Information Design, Bentley University
HF700: Human Factors Foundations
Dr. WM Gribbons
October 19, 2020
Efficiency in human perception aids in identification of survival features and effectively optimizes functionality by “processing only items containing the attended features and blocking others (i.e., forming an attention filter)” of the surrounding environment(Chubb, Wright, Sperling, 2016). In primitive visual processing, brain engages in “detection and localization” of patterns or groups, which share common perceptual qualities and characteristics as part of the early-stage perceptual system(Hughes, Caplovitz, Loucks, Fendrich, 2012). Representation should be “designed to make use of the human visual system”(Healey, 1995).
This paper will examine visual patterns employed by the interface of Rhino 6 3D modeler to provide design recommendations within the context of the early-stage perceptual system to initially draw attention to specific areas of the display interface(Healey, Booth, & Enns, 1995).
Preattentive Processing, Early Stage Perceptual Organization
Efficiency drives primitive human perceptual organization, derived from low-level human vision. The perceptual processing system instantly removes redundancy, compresses information stimuli, and organizes a scene holistically for the brain to prioritize processing most critical environmental inputs from sensory receptors. Visual processing stages include “detection, search, and attention phenomena”(Schneider, Shiffrin, 1977). While there may be debate regarding extent of theories around perception pattern building, Treisman can be credited with identifying the term: preattentive processing, “early preattentive level of processing at which simple features are coded spatially in parallel”(Treisman, 1985). Information processes occur on a continuum across: biological detection; pre-attentive perceptual organization; and cognitive meaning and semantic organization of early-attentive and fully engaged. The neurological factors in visual pattern perception begin with eye fixation as “saccades,” “rapid eye movements with velocities as high as 500ms”(Rayner, 1988). When searching a visual field for an item, preattentive processing focuses the eyes and brain on stimuli of particular characteristics at a “single glance” for visual tasks of approximately 250ms(Healey et al., 1995). The brain prioritizes the “visual system based on operations believed to be rapid, automatic and spatially parallel”(Healey et al., 1995).
These perceptual properties translate into design implications that drive predelivery of attention through unified patterns as part of the efficiency principle, allocating attention guidance. Neurological properties enable preattentive processing, a bottom-up process driven by “local feature contrast” of the stimulus, to preserve, recognize, and transmit signals(Wolfe, Utochkin, 2019).
Neurological Aspects of Pattern Perception
External stimuli are processed as visual images in the form of light initially passing through optical components to the retina for signal translation in later stages of visual processing. Beginning in the retina, visual processing system is neurologically engineered to preserve image spatial structure and augment human vision for greater contrast as edge detection enhances contextual contours by firing nerve endings in the eyes. “Color adaptation of orientation-specific edge-detectors” enables the eye to amplify and preserve appropriate contextual stimuli(McCollough, 1965).
The retina initiates “parallel and hierarchical organization” of the visual system(Lennie, 1998). It contains an optic disc and blind spot at the head of the optic nerve. Here, receptive field centers of retinal output neurons, retinal ganglion cells, converge to preserve and transmit inverted visual maps as M- and P-cells. These cells, distinguished by cell size and action potential propagation sensitivity and speed, carry signals to succeeding stages first intersecting at the optic chiasm and then leaving the eye via the optic tract. These ordered samples of the visual field, “seeded by the spatial interference of ON- and OFF-center retinal receptive field mosaics” depict retinotopic mapping, “a mechanism [that] predicts a link between the layout of orientation preferences around singularities of different signs and the cardinal axes of the retinotopic map”(Paik, Ringach, 2011). Perceptually relevant mapping information “is resurrected in the pattern of connections formed by axonal projections in the lateral geniculate nucleus,” the termination of most retinal ganglion cells in a synaptic relay(Wandell, Winawer, 2011). So that “analysis [of] all dimensions of the image remain intimately coupled in a retinotopic map” for visual processing(Lennie, 1998).
The lateral geniculate nucleus (LGN), located deep in the thalamus, processes and organizes projections from the retina of the contralateral and ipsilateral eye into parallel into six distinct layered cell structures. These cell layers share information characteristics as groups of retinal inputs: one for visual acuity and color, and another for motion and contrast. Along the temporal lobe is the ventral pathway, integral to object location; it contains relatively large magnocellular cells, M-cells, projected from the M ganglion cells to form the magnocellular layers of the LGN. M-cells are primarily responsible for detection of movement, including location, speed, and direction. Along the parietal lobe is the dorsal pathway, key to object recognition; it contains relatively smaller parvocellular cells, P-cells, to form the parvocellular layers. P-cells are critical to fine structure and detailed analysis of shape, size, and color. M- and P-cells project information to the posterior portion of the occipital lobe of the primary visual cortex, also the striate cortex or V1, and secondary visual cortex, V2.
Together, V1 and V2 enable the majority of visual processing by specialized neurological cellar structures, which identify and enhance perceptual patterns. V1 is primarily responsible for visual recognition and spatial arrangement, enabled by orientation columns that detect edges of objects in visual stimuli. Retinotopic organization of V1 cells aligns a corresponding map in both the retina and primary visual cortex. The visual stimuli, inverted in two dimensions, horizontal and vertical, are translated and processed along with the third dimension, depth. Depth consists of biological and learned origins. The biological origins pertinent to preattentive processing can be attributed to retinal disparity between the eyes, convergence of eye rotation; accommodation in lens shape; and motion parallax. While the primary cortex discriminates between lines and edges, V2 mainly interprets color. V2 drives color constancy, a phenomenon that allows humans to perceive objects in the same color by comparison of ambient and estimated illumination levels. V3 and V4 further refine this process in the inferior temporal lobe, enabling object recognition, and in the parietal lobe, guiding motion and spatial awareness. The rapid holistic processing and interpretation of objects and spatial relationships in visual perception exemplifies efficiency in the human visual system.
Physiological Aspects of Pattern Perception
Perceptual organization is based on shared qualities and characteristics. Automatic and immediate neurological tuning of the human visual system identifies patterns to prioritize cognitive processes into discernible and interpretable inputs. Several contributing theoretical models represent best thinking on human perceptual processes. The theory of feature mapping, posed by Treisman, dissects human early vision into a practical number of parallel sets of feature maps coordinated by a master map of locations to articulate preattentive processing. Each feature map corresponds to response activity with unique preattentive features of perception including each of the human vision color primaries, orientation, shape, texture, etc. Because feature maps are parallelly encoded, feature detection is near instantaneous. Individual feature maps indicate activity level, while the master map provides the compilation of spatial, locational, and relational information for focused attention (Treisman, 1985). A related notion identifies parallel processing, the ability of the brain to simultaneously process varying stimuli in the early stages of perceptual organization, which proceeds guided search (Cave, Wolfe). Feature Integration Theory (FIT) posits two stages in the formation of complete perception. In the initial preattentive stage, individual features are “registered early, automatically, and in parallel, while objects are identified separately” in a later stage requiring focused attention (Treisman & Gelade, 1980). This is evidenced by saccade localization speed of a visual search, “averaged latency for conjunction search was longer than for simple search” (McSorley & Findlay, 2001). Spatial pre-cues designed to attract attention prior to the occurrence of change ensure that a feature's identity is encoded(Hughes et al., 2012).
Building upon these theories, Similarity Theory depicts the relationship between the identification processes and discriminability of characteristics between target stimuli and context. It suggests that “‘attention’ (access to visual short-term memory) is seen as a competitive interaction between display elements” illustrated by the direct correlation between increased efficiency and increased visual distinction between targets and nontargets(Duncan, 1989). Search efficiency is interpreted as a continuum guided by target-nontarget similarity and amplified by perceptual groups that may further suppress spreading of nontarget stimulus(Duncan & Humphreys, 1989).
Other factors of pattern perception include: habituation “as a decrement in response as a result of repeated stimulation not due to peripheral processes like receptor adaptation or muscular fatigue”(Thompson, 2001); salience an awareness of stimulus that surpasses suggested strength, guided by distinct requirements; normalizing of situational context; and words relative power.
Pattern Perception & Design Review
Patterns and grouping set the foundation of the primitive organization in early-stage perceptual systems to guide attention to ultimately predict interaction expectations and response. Some significant neurological parameters prioritize the process in which stimuli arrive for observation and while adjacent to the Gestalt laws in application of screen design, new studies present a revised framework of analysis for the neurological basis of pattern and group formation. These parameters are translated into several relevant design principles: figure-ground, proximity, similarity, common region, closure & continuation, and alignment & unity(Chang, Dooley, & Tuovinen, 2002). These perceptual pattern principles are examined in the interface of Rhino 6, the most recent version of Rhinoceros’ 3D computer modeling software program that enables architects, designers, and engineers to digitally create, render, and animate points, lines, curves, and surfaces (Figure 01).
Figure 01: Rhino Interface; Proximity and Similarity
Figure 02: Rhino Interface; Figure Ground, Common Region, Symmetry, and Alignment
Proximity (1): The design principle of proximity is said to be the most fundamental of grouping principles(Kubovy, Holcombe, & Wagemans, 1998). “The law of proximity states that items placed near each other appear to be a group”(Fisher and Smith-Gratto, 1999). This creates a visual grouping that further suggests structure unitization and relationship/relative significance. Rhino 6 displays this type of grouping mechanism with most of its functional components as seen at tag 1 to access commands. The individual commands, represented as icons, maintain consistent spacing which indicates the similar operability of ‘clicking’ to access the operation while the type area of “Command” is offset above the other icons, indicating a difference of interaction expectation, the action of typing to access the command from an autofill list. Proximity enables a user to visually perceive various groups of components to ascertain distinct access operability. To further improve upon this design, the designers could expand on the use of proximity for the command icons located in the left panel to delineate not only access operability but also functionality of commands.
Similarity (2): The similarity principle, also the constancy principle, pertains to the shared characteristics of shape, size, color, sound, and motion also referred to as the “common fate principle.” Color using attention filters of variations in hue then to be the most selective in discriminability for preattentive processes(Sun, Chubb, Wright, Sperling, 2016). Further, colorproperties studies “showed that, even in cluttered environments, certain hues helped in the reduction of search times(Jansson, Marlow, Bristow, 2004). In this instance, Rhino employs similar sizes for command icons on the left panel and further uses colors to indicate similar functionality of icons as seen in tag 2. Each command icon is centered in its allocated button, similar in size to adjacent icons. All blue instances represent a surface function while orange represents a break function. These shared characteristics of the command icons indicate a shared relationship of access operability or functionality.
Figure Ground (3): The next design principle relies on contrast and contextual connection. Within the visual field, human perceptions distinguish foreground from background as a figure ground(Chang et al., 2002). Spatial resolution, neurologically amplified, allows viewers to more rapidly distinguish stimuli within a visual field. Contrast provided by the grid system of Rhino 6 enables a user to better comprehend the spatial implications of the modeling properties of the interface. This provides spatial context for not only the content of the 3D modeling space but also to differentiate this space from other panels, creating a comprehensive workspace for users, appropriate to intended functionality of the interface and program.
Common Region (4): The principles of common region indicate that elements appear grouped when enclosed within the same region. Exemplified in Rhino 6, panels are separated by enclosed regions to indicate grouping of operability and functionality. The interface clearly separates commands and options based upon use, which is key for its audience and their respective purposes.
Symmetry (5): Symmetry and unity are often related. Unity is based upon a “Unity implies that a congruity or arrangement exists among the elements in a design”(Lauer, 1979). The symmetry of the overall interface: 3D modeling spaces at the center, surrounded by panels of similar shape and style, indicate functionality and offer visual unity for ease of use.
Alignment (6): The principles of alignment drive perception of wholes, alignment of oriented units visually suggests a continuation, providing a legible and navigable interface. A user derives groups from alignment in the interface of Rhino 6; it is apparent that items in alignment likely have a similar functionality.
Figure 03: Rhino 6 Desktop Interface
Conclusion and Design Implications
Designers should select the optimum perceptual signal(s) based on attention and bandwidth requirements. Some concrete design implications include: active white space communicates a relationship, proximity assumes a relationship, distance communicates a lack of relationship, consistency and similarity of principles (design patterns/style guide: color, size, etc) aids predictably.
These design implications optimize primitive human perceptual organization of the brain, which detects patterns or groups, to prioritize a scene holistically for processing, interpretation, and reaction of a stimulus within an environment.
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