Subliminal perceptions are those that involve stimuli occurring too weakly or quickly to be recognized consciously. When these were first discovered, there was much excitement and concern over the potential applications of non-conscious perceptions to the field of advertising. Although many subliminal ads were created and tested, it has since become apparent that they are largely ineffective. Although subliminal perceptions can alter behavior in laboratory settings, they fail to have a significant impact on human behavior—especially in the area of complex decision making that interested marketers. Subliminal perceptions also fail to produce significant changes in emotions, and—if anything—have a weak or negligible effect at best.

The minimum amount of energy for a stimulus to be registered as a sensation is known as the absolute threshold. Any stimulus that occurs too weakly to surpass this threshold will not result in a sensation, and will thus be undetected.

The just noticeable difference refers to the minimum amount of change in a stimulus necessary for a difference in its intensity to be recognized.

Transduction is the conversion of energy from one form into another, for example, from light energy into electrical energy during vision.

The minimum threshold may sound like the correct answer, but it is in fact not the correct term. The absolute threshold is the appropriate label for the phenomenon.

"Subliminal" is defined as "beneath the threshold" and it refers to information which is processed without entering into consciousness. Such information has been demonstrated to impact decision making in laboratory conditions, but failed to provide a significant enough influence to justify its use in advertising or politics. This allayed the concerns over a possible "brainwashing" of the public by the media which arose when this phenomenon was discovered.

Though in Freudian terminology the subconsciousness is described as a component of mental life which is inaccessible to regular consciousness, "unconsciousness" does not match this or the correct answer to the question. Finally, subliminal information is not "paranormal," or outside of the natural laws of physics, in any regard, and neither is it "subtypical", which is in fact, not a word at all.

Photoreceptor cells are found only in the "retina" of the eye and house the rods and cones, which break down in the presence of light. This allows the transduction of light energy into electrical energy within the nervous system, which is channeled back to the visual centers of the brain for processing.

The other choices are incorrect. The "lens" is responsible for focusing light onto the retina and the photoreceptor cells that comprise it. The "ciliary muscles" control the shape of the lens when focusing on objects, while the "sclera" is the hard, white, outer surface of the eye. Neither of these areas contain photoreceptors.

All light is received in the rear chamber of the eye on the retina. The place where the nerves exit the eye to go to the brain is also on the retina and it takes up some space. This creates a spot where we can't see anything: it is called a blind spot. Peripheral vision occurs when light is sensed that is not in the clearest part of our vision (e.g. not on the fovea), and can be observed when we see something "out of the corner of our eye.” Nearsightedness and farsightedness occur when the visual focus is a little in front of or a little behind the retina.

The stages of cognitive development, according to Jean Piaget, are the sensorimotor, preoperational, concrete operational, and formal operational. During the sensorimotor stage, the period between birth and age two, cognitive development is limited to motor responses caused by sensory stimuli.

Between ages two and six—the preoperational stage—the child learns to use language. Between ages seven and eleven—the concrete operational stage—children begin thinking logically. During the formal operational stage, age twelve through adulthood, people develop the ability to think about abstract concepts such as deductive reasoning.

The trichromatic theory is one of the oldest theories about why and how humans see in color and it states that there are three types of cones in the retina that can detect the three colors (hence trichromatic) of blue, green, and red.

As for the other answers, dichromatic theory and trichronological theory don't exist; they just sound similar to the correct answer. Place theory and frequency theory are theories about audition rather than vision. Place theory states that ear hairs respond to different frequencies based on their different locations in the cochlea, and frequency theory states that pitch is perceived by the rate at which hair cells fire.

Transduction is an essential stage of perception. This is when energy is converted from one form into another: namely, from light, chemical, or physical energy from incoming stimuli into electrical energy within the nervous system. Without this key step, perception as we know it would be impossible. To name a few examples, this process occurs with in the retina of the eyes, within the cochlea of the inner ears, within the olfactory receptors of the nose, and within gustatory receptors within taste buds on the tongue.

Transduction does not involve the amplification of energies; furthermore, it does not involve screening or analysis of information for any specific purposes. This occurs at the level of the brain, not within receptor cells, where transduction occurs.

The middle ear contains three tiny bones: the malleus (hammer), the incus (anvil), and the stapes (stirrup). These bones concentrate the vibrations coming from the eardrum, and send these signals to the cochlea's oval window.

Each region of the ear uses a different medium to transmit vibrations. Remember that the outer ear uses air as the medium (sound waves impact the ear drum). The middle ear uses bones to transmit these vibrations to the oval window. Finally, the inner ear uses fluid found in the cochlea to transmit the vibrations to neural tissue.

The lens is a crystalline structure within the eye. Like the lens in corrective glasses or contact lenses, the lens of the eye focuses light. In this case, it focuses light onto the photosensitive retina at the rear of the eye. The lens has an important role in vision because objects at different distances will reflect light at different angles. If we were unable to focus this variable light by means of the lens, then perceived images outside of a certain distance would appear unfocused and blurry.

You can test this through a simple experiment. First, try to focus your gaze on an object less than a foot away from your head, then stare at something several feet away, and finally stare at something far away (e.g. out of your window). If the direction of your gaze has remained relatively constant, then part of the physical sensation you are feeling in your eyes is the lenses changing to focus the different images onto the retina.

On the other hand, the lens is not responsible for locating an image; muscular movements of the head and eyes control where and what they look at. Furthermore, the lens cannot not accommodate for the blind spot. Instead, binocular vision helps in filling in for missing visual details. Last, the lens does not control how much light enters the eye—that is the job of the pupil and iris. The lens merely controls the focusing of that light onto the retina.