Reading Notes: June 21st, 2022

“In his “Refutation of Idealism,” Moore held that the main contention of idealists was “esse est percipi,” and that the plausibility of this contention depended upon a failure to make a certain distinction….In the sensation of green, for example, we may distinguish what it has in common with other sensations, namely its being an act of awareness, from what distinguishes it from others, namely the green that is the object of this awareness. There is no doubt that the sensation, regarded as an act, is mental; but this has no tendency to show that the sensation, regarded as the object of the act, is likewise mental….Mr. Harris believes that Moore’s refutation is invalid. The chief argument he offers against it seems to be that it proves too much, since the same kind of confusion that is involved in taking about the sensation of green is involved in talking about green alone. Moore charged that when the idealist identified “blue exists” with “the sensation of blue exists”, he was contradicting himself, because he was either identifying the part with the whole—the object with object-plus-awareness—or identifying one part of this whole with the other—the object with the awareness of it. Now suppose that, following Moore, you mention that green exists independently. Within this existent green we can also distinguish two features, the existence that it has in common with other qualities, and what sets it off from these, the quality green. And when Moore says, in his own sense, “green exists”, he must be either identifying the part, or quality, with the whole—quality-plus-existence—or identifying one part with the other, quality with existence. In either case he is contradicting himself in the same fashion as he alleged Berkeley to have done.” (Blanshard, Nature, Mind, and Modern Science, 168-169) 

“Speech, music, and every other sound one hears can be described by the pattern of amplitude at different frequencies. This pattern, which is called the sound’s spectrum, distinguishes one sound from others. In human speech, for example, the vowel in the word heat sounds different from the vowel in hat because amplitude peaks occur at different frequencies in the spectrum of the first vowel. Frequency analysis, described in this entry, refers to the ability to process different regions of the spectrum separately. This ability allows a person to discriminate two tones of different frequencies, but more importantly, it allows the locations of the amplitude peaks in the spectrum of any sound to be encoded and represented in the brain. Frequency analysis begins in the cochlea, where the spectrum of the acoustic signal is converted to a representation called a place code for frequency. The place code for frequency that is created in the cochlea is preserved as the signal is represented in the responses of neurons and processed in the brain. Throughout the auditory system, the representation of frequency by a neural place code is the predominant organizational principle.” (Sinex, Entry on “Auditory Frequency Selectivity” in The Encyclopedia of Perception, 158) 

“Attention is the mechanism that allows us to select relevant information for processing from the vast amount of stimuli we are confronted with, prioritizing some while ignoring others. Attention can affect perception by altering performance—how well we perform on a given task—or by altering appearance—our subjective experience of a stimulus or object….There are two systems of covert attention: endogenous and exogenous. Endogenous attention refers to the voluntary, sustained directing of attention to a location in the visual field….Exogenous attention refers to the automatic, transient orienting of attention to a location in the visual field, brought about by a peripheral cue or a sudden abrupt onset of a stimulus at the location.” (Carrasco, Entry on “Attention’s Effect on Perception” in The Encyclopedia of Perception, 90-91) 

“Physiological research suggests that spatial attention is controlled by a network of brain areas that includes the frontal and parietal cortex, as well as subcortical areas. Neurons in most of these areas are organized into maps that represent locations in the environment. The level of neural activity at a given location in the map is thought to represent the physical salience and behavioral relevance of stimuli at the corresponding location in the environment. The cells on the map having the greatest activity correspond to the most important location in the environment, and the greatest amount of attention is directed to this location. The assumption is that these maps influence sensory processing by modulating the activity of sensory neurons….When attention is focused on a stimulus, sensory neurons encoding that stimulus tend to increase their firing rates, resulting in an amplification of the neural response to the attended stimulus….The amplification of neural responses to an attended stimulus can have important implications when multiple stimuli are present in the environment. For example, in the visual system, each sensory neuron responds to visual stimulation within a restricted region of the visual field, called its receptive field….A salience map is a topographical representation of external space that is laid out across the surface of a neural structure, such as the frontal eye field, posterior parietal areas, or superior colliculus. The activity of the neurons composing this map is affected by both the physical salience and the behavioral relevance of stimuli in the environment.” (McPeak, Entry on “Physiological Attention” in The Encyclopedia of Perception, 99-100) 

“We experience the world around us, in all its sensory detail and complexity, directly—or at least so we believe. Yet a simple test reveals that our sense of direct experience may be misleading….Attention is the portal though which sensory information is selected for more detailed examination, classification, and registration….Sensory inputs arrive by stimulating sensory systems in the eye (or ear, or skin) that respond to specific patterns of light (or sound, or touch). Different cells in brain areas that process the sensory inputs respond to different patterns, and specific locations or objects often stimulate neurons in different locations in the brain. When you look at the visual world, sensory responses to the many stimuli across the visual field occur simultaneously, or nearly simultaneously, in parallel. They constitute a “blooming, buzzing” collection of sensory inputs or representations. Selective attention picks out the relevant from the irrelevant, the focus from the background. Many theorists have argued that attention selects one thing (or perhaps a few things) at a time for processing. So, they felt, this implied the processing of visual inputs serially—one after the next in time in a series.” (Dosher and Lu, Entry on “Selective Attention” in The Encyclopedia of Perception, 101)