Perception

Human perception is taken here as the physicochemical interface between the outside world and the human brain, plus the sensory and cognitive processing of the data transforming these into information. Each sense organ is generally activated by its specialized type of stimulation and gives rise to its specific set of sensory attributes. Senses that take in stimulation from distant sources are hearing, through certain acoustical vibration, vision, through certain electromagnetic radiation, and smell, by a number of volatile chemical substances. Sense organs that react to stimulation from close sources are taste, by certain chemical substances in the mouth, and the skin senses (and kinesthetic senses), from mechanical stimulation at the outside or inside of the body. Within each of the senses, the sensory attributes and their dynamic variations are subjected to processes of recognition, i.e., interpreted within a framework of evolved experience and recent context. An important special case is the recognition of spoken language (speech) through the ear or written language (reading) through the eye, where the language elements are symbolic carriers of information between humans. In the overwhelmingly rich sensory stimulation to which humans are exposed, powerful perceptual selection processes make the chaotic input amenable. All perceptual functions are far from constant because they are in active development over life from one's earliest to final moment

Contrast, noise and blur affect performance ad appreciation of digital radiographs

We have studied the effect of the simultaneous variation of contrast, noise, and blur on the perceived quality of digital radiograph images. Three images were processed with different levels of roentgen photon noise, different luminance (gray-level) ranges, and different amounts of Gaussian blur. Observers had to rate the quality of the images on a numerical scale. To study how the quality judgment is related to the visibility of small details (diagnostic quality), an artificial detail was added to each image. The detail could be in two possible locations. The visibility of this detail was measured in a two-alternative forced-choice experiment. One of the conclusions is that the quality judgment was based mainly on blur, whereas the visibility of details was affected mostly by noise