Human visual perception is a parallel process where one can process visual information in his/her/3rd gender field of view/visual field simultaneous with brain neurons controls order of precedence of perception (serialization of visual information by neural system). Sensor system process visual information in five stages i.e. Transduction, where physical stimulus energy is transformed to a neural signal, in this stage intensities are encoded and intensity changes will be responded accordingly. Wavelength and energy of light plays important factor in intensity variations. Visual encoding, process of encoding images and visual sensory information and creation of mental pictures is one way people use visual encoding. The amygdala plays a large role in the visual encoding of memories. Neural pathway of vision, a pathway over which a visual sensation is transmitted from the retina to the brain consists of optic nerve, fibers of optic nerve and optic signals/ radiations. Receptive fields, help in image/object recognition and visual memory. In this stage, important attributes of image/object are perceived such as shape, color, depth, movement. Visual Topography, is a representation of visual field of view and mapping on to cerebral cortex of neural system.
This is section is a summary of two papers “Crowdsourcing Graphical Perception by Jeffrey Heer and Michael Bostock” and “Graphical perception by William S. Cleveland and Robert McGill”. Perception is key to visualization of data, one of the paper discussed about the crowdsourcing in visualization experiments over laboratory experiments and discusses ecological viability, subject motivation and expertise. Other important aspects to visual perception such as device display configuration and viewing environment of participating subject. Authors investigated effects of environmental context and conditions like display type, display size, lighting, and subjects’ viewing distance and angle on visual perception research. Visual variables i.e. position, length, area, shape and color key factor that can impact the effectiveness of data visualization. Source and domain of data are also important in visualization experiments. Impact of complexity of visual encoding on graphical perception helps to optimize the visualization. Experiments are done on proportions such as anlge, length etc theoretically length performs better than angle, angle performs better than area. But experiments suggested that there is no comparison between position-angle and position-length. From the rectangular area judgement experiments it is found that there is no significant difference between tree map and rectangle. Plot density has significant effect on graphical perception over background density which is consistent with previous findings. Chart size and grid line spacing, charts that are 40 px tall are prone to more error, accuracy of perception increases with height but to a certain extent. Charts that are over 80 px has no significant improvement in the graphical perception additionally, adding gridlines improve the accuracy. From the experiment, it is recommended gridlines spacing of 8 px and dense packing of graphs usually reduce the accuracy. Crowdsourcing experiments helps to reduce cost and time with control over experiments as trade-off.