Kristina Armitage/Quanta Magazine
Two years ago, Sarah Shomstein realized she didn’t have a mind’s eye. The vision scientist was sitting in a seminar room, listening to a scientific talk, when the presenter asked the audience to imagine an apple. Shomstein closed her eyes and did so. Then, the presenter asked the crowd to open their eyes and rate how vividly they saw the apple in their mind…….Continnue reading…..
By: Yasemin SaplakogluSource: Quanta Magazine
. Critics:The process of perception begins with an object in the real world, known as the distal stimulus or distal object. By means of light, sound, or another physical process, the object stimulates the body’s sensory organs. These sensory organs transform the input energy into neural activity—a process called transduction. This raw pattern of neural activity is called the proximal stimulus.
These neural signals are then transmitted to the brain and processed. The resulting mental re-creation of the distal stimulus is the percept. To explain the process of perception, an example could be an ordinary shoe. The shoe itself is the distal stimulus. When light from the shoe enters a person’s eye and stimulates the retina, that stimulation is the proximal stimulus. The image of the shoe reconstructed by the brain of the person is the percept.
Another example could be a ringing telephone. The ringing of the phone is the distal stimulus. The sound stimulating a person’s auditory receptors is the proximal stimulus. The brain’s interpretation of this as the “ringing of a telephone” is the percept. The different kinds of sensation (such as warmth, sound, and taste) are called sensory modalities or stimulus modalities.
- When people encounter an unfamiliar target, they are very open to the informational cues contained in the target and the situation surrounding it.
- The first stage does not give people enough information on which to base perceptions of the target, so they will actively seek out cues to resolve this ambiguity. Gradually, people collect some familiar cues that enable them to make a rough categorization of the target.
- The cues become less open and selective. People try to search for more cues that confirm the categorization of the target. They actively ignore and distort cues that violate their initial perceptions. Their perception becomes more selective and they finally paint a consistent picture of the target.
According to Alan Saks and Gary Johns, there are three components to perception:
- The Perceiver: a person whose awareness is focused on the stimulus, and thus begins to perceive it. There are many factors that may influence the perceptions of the perceiver, while the three major ones include (1) motivational state, (2) emotional state, and (3) experience. All of these factors, especially the first two, greatly contribute to how the person perceives a situation. Oftentimes, the perceiver may employ what is called a “perceptual defense”, where the person will only see what they want to see.
- The Target: the object of perception; something or someone who is being perceived. The amount of information gathered by the sensory organs of the perceiver affects the interpretation and understanding about the target.
- The Situation: the environmental factors, timing, and degree of stimulation that affect the process of perception. These factors may render a single stimulus to be left as merely a stimulus, not a percept that is subject for brain interpretation.
The timing of perception of a visual event, at points along the visual circuit, have been measured. A sudden alteration of light at a spot in the environment first alters photoreceptor cells in the retina, which send a signal to the retina bipolar cell layer which, in turn, can activate a retinal ganglion neuron cell. A retinal ganglion cell is a bridging neuron that connects visual retinal input to the visual processing centers within the central nervous system. Light-altered neuron activation occurs within about 5–20 milliseconds in a rabbit retinal ganglion,
Although in a mouse retinal ganglion cell the initial spike takes between 40 and 240 milliseconds before the initial activation. The initial activation can be detected by an action potential spike, a sudden spike in neuron membrane electric voltage. A perceptual visual event measured in humans was the presentation to individuals of an anomalous word. If these individuals are shown a sentence, presented as a sequence of single words on a computer screen, with a puzzling word out of place in the sequence, the perception of the puzzling word can register on an electroencephalogram (EEG).
In an experiment, human readers wore an elastic cap with 64 embedded electrodes distributed over their scalp surface. Within 230 milliseconds of encountering the anomalous word, the human readers generated an event-related electrical potential alteration of their EEG at the left occipital-temporal channel, over the left occipital lobe and temporal lobe. Cognitive theories of perception assume there is a poverty of the stimulus.
This is the claim that sensations, by themselves, are unable to provide a unique description of the world. Sensations require ‘enriching’, which is the role of the mental model. The perceptual ecology approach was introduced by professor James J. Gibson, who rejected the assumption of a poverty of stimulus and the idea that perception is based upon sensations. Instead, Gibson investigated what information is actually presented to the perceptual systems. His theory “assumes the existence of stable, unbounded, and permanent stimulus-information in the ambient optic array.
And it supposes that the visual system can explore and detect this information. The theory is information-based, not sensation-based.”He and the psychologists who work within this paradigm detailed how the world could be specified to a mobile, exploring organism via the lawful projection of information about the world into energy arrays.”Specification” would be a 1:1 mapping of some aspect of the world into a perceptual array. Given such a mapping, no enrichment is required and perception is direct.
Perception is an important part of the theories of many philosophers it has been famously addressed by Rene Descartes, George Berkeley, and Immanuel Kant to name a few. In his work The Meditations Descartes begins by doubting all of his perceptions proving his existence with the famous phrase “I think therefore I am”, and then works to the conclusion that perceptions are God-given.
George Berkely took the stance that all things that we see have a reality to them and that our perceptions were sufficient to know and understand that thing because our perceptions are capable of responding to a true reality. Kant almost meets the rationalists and the empiricists half way. His theory utilizes the reality of a noumenon, the actual objects that cannot be understood, and then a phenomenon which is human understanding through the mind lens interpreting that noumenon.
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