A perspective is the choice of a context or a reference, or the result of the choice, from which to sense, categorize, measure or codify experience, cohesively forming a coherent belief, typically for comparing with another. One may further recognize a number of subtly distinctive meanings, close to those of paradigm, point of view, reality tunnel, or worl view.

To choose a perspective is to choose a value system and, unavoidably, an associated belief system. When we look at a business perspective, we are looking at a monetary based value system and belief. When we look at a human perspective, it is a more social value system and its associated beliefs.

In social psychology one would talk in terms of the other person’s point of view when soliciting or motivating the other person to do something for you. Being able to see the other person’s point of view is one of Henry Ford’s advice towards being successful in business. “If there is any one secret of success, it lies in the ability to get the other person’s point of view and see things from that person’s angle as well as from your own”.

Perspection, a related concept, signifies the ability to inspect one’s own perception, or the perceive another individual’s inspection.

Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and by sensory cells of the antennae of invertebrates.

The importance and sensitivity of smell varies among different organisms. Most mammals have a good sense of smell, whereas most birds do not. Among mammals, it is well-developed in the carnivores and ungulates, who must always be aware of each other, and in those that smell for their food, like moles.

It is estimated that dogs have an olfactory sense approximately a hundred thousand to a million times more acute than a human’s. This does not mean they are overwhelmed by smells our noses can detect, rather, it means they can discern a molecular presence when it is in much greater dilution in the air. 

Bears, such as the Silvertip Grizzly found in parts of North America, have a sense of smell seven times stronger than a dog, essential for locating food underground. Using their elongated claws, bears dig deep trenches in search of burrowing animals and nests as well as roots, bulbs, and insects. Bears can detect the scent of food from up to 18 miles away.

Fish also have a well-developed sense of smell, even though they inhabit an aquatic environment. Salmon utilize their sense of smell to identify and return to their home stream waters. Catfish use their sense of smell to identify other individual catfish and to maintain a social hierarchy.

Insects use their antennae for olfaction. Sensory neurons in the antenna generate electrical signals called spikes in response to odor. The antennae have sensory neurons in the sensilla with axons terminating in the antennal lobes where they synapse with other neurons in semidelineations called glomeruli.

The cocktail party effect describes the ability to focus one’s listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. This effect reveals one of the surprising abilities of our auditory system, which enables us to talk in a noisy place.

The effect can occur both when we are paying attention to one of the sounds around us and when it is invoked by a stimulus which grabs our attention suddenly. For example, when we are talking with our friend in a crowded party, we still can listen and understand what our friend says even if the place is very noisy, and can simultaneously ignore what another nearby person is saying. Then if someone over the other side of the party room calls out our name suddenly, we also notice that sound and respond to it immediately.

It was first described and named by Colin Cherry in 1953. Much of the early work in this area can be traced to problems faced by air traffic controllers in the early 1950s. At that time, controllers received messages from pilots over loudspeakers in the control tower. Hearing the intermixed voices of many pilots over a single loudspeaker made the controller’s task very difficult.

Cherry conducted attention experiments in which subjects were asked to listen to two different messages from a single loudspeaker at the same time and try to separate them. His work reveals that our ability to separate sounds from background noise is based on the characteristics of the sounds, such as the gender of the speaker, the direction from which the sound is coming, the pitch, or the speaking speed.

This phenomenon is still very much a subject of research, in humans as well as in computer implementations, where it is typically referred to as source separation or blind source separation. The neural mechanism in human brains is not yet fully clear.

Rubin’s vase is a famous set of cognitive optical illusions developed around 1915 by the Danish psychologist Edgar Rubin. The illusion generally presents the viewer with a mental choice of two interpretations, each of which is valid. Often, the viewer sees only one of them, and only realizes the second valid interpretation after some time or prompting. When the viewer attempts to simultaneously see the interpretations together, they suddenly cannot see the first interpretation anymore, and no matter how they try they simply cannot encompass both interpretations simultaneously; one occludes the other.

The illusions are useful because they are an intuitive demonstration of the figure-ground distinction the brain makes during visual perception. Rubin’s figure-ground distinction influenced the Gestalt psychologists, who discovered many similar illusions themselves. It involves higher-level cognitive pattern matching in which the overall picture determines its mental interpretation, rather than the net effect of the individual pieces.

Normally the brain classifies images by what surrounds what, establishing depth and relationships. If something surrounds another thing, the surrounded object is seen as figure, and the presumably further away (and hence background) object is the ground, and vice versa. This makes sense, since if a piece of fruit is lying on the ground, one would want to pay attention to the “figure” and not the “ground”.

However, when the contours are not so unequal, ambiguity starts to creep into the previously simple inequality and the brain must begin “shaping” what it sees. It can be shown that this shaping overrides and is at a higher level than feature recognition processes that pull together the face and the vase images. One can think of the lower levels putting together distinct regions of the picture (each region of which makes sense in isolation), but when the brain tries to make sense of it as a whole, contradictions ensue, and patterns must be discarded.

The Ganzfeld effect is a phenomenon of visual perception caused by staring at an undifferentiated and uniform field of color. The effect is described as the loss of vision as the brain cuts off the unchanging signal from the eyes. The result is “seeing black” or apparent blindness. The word is from German for “complete field”.

The effect is the result of the brain amplifying neural noise in order to look for the missing visual signals. The noise is interpreted in the higher visual cortex, and gives rise to hallucinations. This is similar to dream production because of the brain’s state of sensory deprivation during sleep.

The Ganzfeld effect has been reported since ancient times. The adepts of Pythagoras retreated to pitch black caves to receive wisdom through their visions. Miners trapped by accidents in mines frequently reported hallucinations, visions and seeing ghosts when they were in the pitch dark for days. Arctic explorers seeing nothing but featureless landscape of white snow for a long time also reported hallucinations and an altered state of mind.

In Tibetan Buddhism a dark retreat refers to advanced practices of isolation in darkness. The time period dedicated to dark retreat varies from a few hours to decades. Dark retreat in the Himalayan tradition is a restricted practice only to be engaged by the senior spiritual practitioner under appropriate spiritual guidance. This practice is considered conducive for navigating the bardo at the time of death and for realising the rainbow body. The traditional dark retreat requires stability in the natural state and is only suitable for advanced practitioners.

Ancient Egyptians and Mayans practiced a form of the dark retreat as well, traditionally lasting 10 days. Holy men would enter into the center of their respective pyramids, completely removed from light and sound, and have visions of the workings of the universe. Today, scientists have hypothesized that when the human body is deprived of visual stimulation, the brain produces a substance called Dimethyltryptamine (DMT), a tryptamine, which results in intense visions.

A phosphene is an optic phenomenon characterized by the experience of seeing light without light actually entering the eye. Phosphenes can be directly induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex as well as by random firing of cells in the visual system. Phosphenes have been reported by meditators and people who go for long periods without visual stimulation (also known as the prisoner’s cinema).

The most common phosphenes are pressure phosphenes caused by rubbing the closed eyes. The pressure mechanically stimulates the cells of the retina. Experiences include a darkening of the visual field that moves against the rubbing, a diffuse colored patch that also moves against the rubbing, a scintillating and ever-changing and deforming light grid with occasional dark spots (like a crumpling fly-spotted flyscreen), and a sparse field of intense blue points of light.

Pressure phosphenes can persist briefly after the rubbing stops and the eyes are opened, allowing the phosphenes to be seen on the visual scene. Herman Helmholtz and others have published drawings of their pressure phosphenes. One example of a pressure phosphene is demonstrated by gently pressing the side of your eye and observing a colored ring of light on the opposite side, as detailed by Isaac Newton.

Another common phosphene is “seeing stars,” from a sneeze, a heavy and deep cough, blowing of the nose, a blow on the head or low blood pressure (such as on standing up too quickly or prior to fainting). It is possible these involve some mechanical stimulation of the retina, but they may also involve mechanical and metabolic stimulation of neurons of the visual cortex or of other parts of the visual system.

Phosphenes have also been created by intense, changing magnetic fields, such as with transcranial magnetic stimulation. These fields can be positioned on different parts of the head to stimulate cells in different parts of the visual system. They also can be induced by alternating currents that entrain neural oscillation as with trancranial alternating-current stimulation. In this case they appear in the peripheral visual field. Astronauts exposed to radiation in space report seeing phosphenes.

Grapheme-color synesthesia is a form of synesthesia in which an individual’s perception of numbers and letters is associated with the experience of colors. Like all forms of synesthesia, grapheme-color synesthesia is involuntary, consistent, and memorable. It is one of the most common forms of synesthesia, and because of the extensive knowledge of the visual system, one of the most studied.

One recent study has documented a case of synesthesia in which synesthetic associations could be traced back to colored refrigerator magnets. Despite the existence of this individual case, the majority of synesthetic associations do not seem to be driven by learning of this sort. Rather, it seems that more frequent letters are paired with more frequent colors, and some meaning-based rules, such as B being blue, drive some synesthetic associations.

These experiences have led to the development of technologies intended to improve the retention and memory of graphemes by individuals without synesthesia. Computers, for instance, could use artificial synesthesia to color words and numbers to improve usability. Individuals with grapheme-color synesthesia rarely claim that their sensations are problematic or unwanted. In some cases, individuals report useful effects, such as aid in memory or spelling of difficult words.

Synesthetes often report that they were unaware their experiences were unusual until they realized other people did not have them, while others report feeling as if they had been keeping a secret their entire lives. Many synesthetes can vividly remember when they first noticed their synesthetic experiences, or when they first learned that such experiences were unusual. Writer and synesthete Patricia Lynne Duffy remembers one early experience:

“One day, I realized that to make an R all I had to do was first write a P and then draw a line down from its loop. And I was so surprised that I could turn a yellow letter into an orange letter just by adding a line.”

An interobject is a phenomenon of dreams, in which there is a perception of something that is “between” two objects. Interobjects differ from typical dream manifestations in which two objects are fused into one. Instead, the object is incomplete. An example from the literature on dreams includes “something between a record player and a balance scale.” Interobjects are new creations derived from partially-fused blends of other objects.

Interobjects, like disjunctive cognitions, would sound bizarre or psychotic as perceptions in waking life, but are accepted by most people as commonplace in dreams. They have implications for both the theory of dreaming and the theory of categorization. Interobjects show the dreaming mind grouping items together whose connection may not be apparent to the waking mind. “Something between an aqueduct or a swimming-pool” reveals the category of “large man-made architectural objects that contain water.” “Something between a cellphone and a baby” reveals a category combining a relatively new piece of technology and a live infant: both make noise when you don’t expect it, both are held close to your body, and both can give you a feeling of connectedness.

Most adults tend to regularize interobjects when discussing them in waking life. Children are better able to sustain interobjects in their original form. A child told his father a dream in which he was in trouble at sea and a seal swam up to them. They thought it was just a seal, but then they looked and under the water it was a whole boat, it was huge, so they climbed onto the seal/boat, and it brought them to the shore of the mainland. When the boy told his father the dream in the morning, the father, speaking like an adult who cannot tolerate contradictions, said to him: “So really, it was a boat, a big, safe boat.” The child, holding fast to the integrity of his dream, said, “It was a boat, but it was still a big, friendly seal.” This child had not yet learned to regularize his perceptions to fit the way the world works. Adults may learn to reject interobjects in waking life, but still retain them in their dreams.

Interobjects may have an elementary function in human thought. By transgressing the normal mental categories described by Eleanor Rosch, interobjects may be the origin of new ideas that would be harder to come by using only fully-formed, secondary process formations. They may be one example of “Oneiric Darwinism” in which new thought-mutations are created during dream-life and rejected or retained in waking life depending on their usefulness.