Sensation and Perception

Stimulus

A quantifiable pattern of physical energy, which is able to interact with an organism and produce a change in the condition of the organism. That is, a stimulus is a type of environmental energy, like light, that we are capable of detecting and responding to--must have the capacity to interact with and stimulate specialized cells in the human body

cutaneous sensitivity

Cutaneous sense (skin sense) refers to touch, pressure, temperature, and pain (nociception)

Closure

Denotes groupings that occur in a way that favors the perception of the more enclosed figure -Priority is given to objects that favor a more symmetrical configuration--the process is continuous and ever-changing

absolute threshold

The lowest intensity of a stimulus that can be sensed and perceived. The intensity level that is detected 50% of the time. -Above threshold means the person will detect the stimulus every time -Below threshold means people can detect the stimulus less than half the time -Absolute threshold differs from person to person

Thresholds

The minimum level of stimulation needed for a neuron to fire an action = the lowest point at which a particular stimulus will cause a response in an organism. -An important means of measuring a sensation is to determine the threshold stimulus--i.e. the minimum energy required to evoke the sensation--the weakest possible stimulus that will still affect the cell's firing

occipital lobe

The part of our brain responsible for processing the visual information

Perceptual aspects of audition

There is a difference between the objective intensity of physical stimulus and the subjective experience of this stimulus (Ernst Weber and Gustav Fehner)

Good continuation

elements that appear to follow in the same direction tend to be grouped together

Sensory fun facts

-Cells form the basis for what most people understand as sensations--sensory experiences produce our perception of the world -Sensory systems provide information to control movement -Protagoras: We are what we sense and percieve

Fun facts about olfaction

-Chemical molecules enter the nostrils and stimulate the olfactory receptors at the top of the nasal cavity. -The olfactory receptor cells are actual neurons. Undergo continuous neurogenesis (reproduction) about once every 25-30 days (only neurons known to reproduce) -The number of olfactory receptors is far fewer than the thousands of distinct smells humans are capable of detecting -So there isn't a one-to-one correspondence between olfactory receptor types and specific smells -Smells are the result of a specific combination of activation for several types of olfactory receptor types and specific smells -Humans have approx. ten million olfactory receptor cells

Perception fun facts

-Perception allows us to be selective and even occasionally ignore unimportant information--the world is guided by your perception -Perception enables us to evaluate the visual stimulus and produce a meaningful answer for this illustration -Perception is a way of processing information

Perceptual aspects of vision

-Perception of the visual information involves your conscious awareness -Brain makes many assumptions based on our expectations and past experiences -Perception attempts to find useful ways to make the most of our surroundings, sometimes even at the cost of misrepresentation of the visual stimulus--causes optical illusions -Gestalt psychologists proposed that people tend to follow a simple rule to organize objects (Law of Pragnanz)--articulated the importance of context and holistic understanding of the world rather than dissecting the environment by an individual stimulus (panda picture). This delineates how we identify and group visual elements -We should see the world in 2D, but we use diverse depth cues around us to access the depth information

Gestalt psychology and perception

-The view that perception is not simply a reduction of complex forms, but a holistic and creative process was first introduced by Gestalt psychology -The brain makes certain assumptions about what is to be seen in the world, and these expectations seem to be derived in part from experience and also from innate neurological wiring -Gestalt grouping may enhance our ability to process complex visual phenomenon by decreasing the time required to understand the individual elements of an object

two theories of attention

-Theories that view attention as a causal mechanism which distinguish between automatic and controlled processes -Theories that see attention as a consequence of other processes, like priming activities for some memory

Process of visual perception: 3 basic tasks

1. Detection 2. Discrimination 3. Identification--How much detail is necessary? -The tasks grow in complexity and it is a very complex process

Factors influencing attention

1. Number of sources--as the number increases, focused attention becomes difficult to maintain 2. The similarity of sources--The more similar the stimuli are, the more divided attention will be (don't listen to music with lyrics while reading) 3. The complexity of the tasks--As the task becomes more complex, it demands more attention 4. Automaticity--As a task (like playing piano) becomes more and more practiced, it requires less and less attention

Attention

A concentrated mental effort that functions as a filter to ignore unimportant events and focus on important events. Crucial in the beginning of perception

Sensory adaptation

A decline in a sensation's sensitivity resulting from the presence of a constant stimulus--sensory receptors become less sensitive when exposed to stimulus for a certain amount of time (e.g. going from sunlight into a dark building) -Retinal receptors adapt very quickly -Vision doesn't fade because eyes constantly make small movements called saccades--exposes eyes to a constant, shifting scene to avoid adaption

Occlusion

A phenomenon in which an object closer to a viewer appears to block another object that is farther away from the viewer--just one example of monocular depth cues

Dual or two-process theory

The idea that we localize low-frequency sounds by using time or phase differences or both

threshold stimulus

A stimulus that is just barely strong enough to affect the receptor -Receptor cells in the eyes are constantly changing their thresholds to match the lighting conditions around you

parvocellular pathway

A visual pathway for central vision and high spatial resolution images. -Serve as the anatomical basis for more localized visual information processing -Retinal images from the left visual field are transmitted to the right hemisphere and vice versa -Each side of the brain hemisphere processes the images from the opposite side of the visual field

"Where" pathway

A visual pathway projected into the parietal lobe that integrates information about the location of an object

"What" pathway

A visual pathway projected into the temporal lobe that responds to and integrates information about size, color, and/or the identity of an object

just noticeable difference (JND)

Also called the difference threshold. The smallest change in magnitude of a stimulus that can be detected.

top-down processing

An information-gathering process starting from an individual's' knowledge, expectations, and prior experiences--emphasized the importance of the context and cognitive structures we have--influenced by more than just the stimulus

bottom-up processing

An information-gathering process, starting from each individual stimulus--doesn't start by including prior knowledge. -Decreases chances of seeing an optical illusion -Both processes tend to co-occur

Merkel receptors

Are activated by steady pressure/skin indentations and are also located in the epidermis of the skin

Ruffini corpuscles

Are activated by steady skin indentations/pressure and are slowly adapting. Are located in the dermis and their receptive field is also large

Meissner's corpuscles

Are sensitive to flutter and are located in the superficial region of the glabrous skin (hairless skin). Their receptive field is small

Monaural cues

Auditory depth perception that occurs with just one ear

Binaural cues

Auditory depth perception that occurs with the use of both ears--like monocular and binocular visual cues.

somethesis

Bodily sensations/ the sense of touch. Made up of two sensory experiences: Kinesthetic sensitivity and cutaneous sensitivity

Inattentional blindness

Diverted attention resulting in failure of accurate scene detection as if we are blind to that event (gorilla scene test). -Research shows that people with well-developed attention tend to be more successful -Video games & TV shows negatively impact the development of attention -Enables people to actively select certain information for further processing

Olfaction

Experiences of smell. Every sense must detect a specific physical stimulus from the environment; for olfaction, the stimulus comes from chemical molecules in the air which are released by the substances we are smelling.

Adaptation

If a stimulus persists for a sustained period of time, its intensity decreases over time (like a body getting used to cold water) -Perception is greatest at the regions of greatest contrast

Kinesthetic sensitivity

Kinesthetic sense refers to knowledge about spatial position and movement information occurring from mechanical stimulation of mobile joints, muscles, and tendons

Equal loudness countours

Lines measuring the function of loudness and frequencies of sound waves -When interpreting sound waves & to detect and increase/decrease in sounds, we must use both frequency (pitch) and amplitude (loudness) information -The auditory system is able to distinguish the location/direction of a sound source and relative distance

polymodal nociceptors

Nociceptors activated by a variety of high-intensity mechanical, chemical, and very hot/very cold stimuli--produces a dull, throbbing pain

thermal or mechanical nociceptors

Nociceptors associated with sensations of sharp, stinging pain

divided attention (multitasking)

Occurs when two or more separate tasks/mental operations are performed simultaneously

Focused/selective attention

One information source must be attended to at the exclusion of other

Singleness of an action

Only part of an image can be selected as the focus of attention; the rest must become part of the background

Weber's fraction

The smallest change in the magnitude of a stimulus that can be detected, expressed as a proportion of the original stimulus

T/F--Our contact with the world typically starts with information reception from our sensory receptors and ends with meaningful interpretation of the environment based on a higher level of information integration at the brain level

TRUE

T/F--Intensity of stimulus used to judge distance of a sound source

TRUE. If two sounds are presented together, the louder one is perceived to be closer

T/F--Perception of pain is affected by a variety of external and internal influences

TRUE. Perception is also affected by psychological and cultural responses to pain-related stimuli

interaural time difference

The slight difference in time sound arrives at one ear before the other ear -If the left ear receives a sound first, the right auditory cortex becomes more active while simultaneously deactivating the left auditory cortex

Perception

The acquisition and processing of sensory information in order to see, hear, taste, or feel objects in the world--also guides an organism's actions with respect to those objects

cognitive overload

The amount of working memory resources dedicated to a specific task with the idea that there is a limit to the amount of processing load a brain can manage --Multitasking also requires cognitive shifts from one source or activity to another

Doppler shift

The change in pitch emitted by an object moving horizontally in space in relation to a stationary observer -Accurate location of a sound-emitting object is only possible with binaural cues

Perception

The detailed process of interpreting and making sense of a combination of sensations -Brain making sense of the physical stimulus from the world by organizing the stimulus into a representation of something useful -Perception is not generally possible without sensation

Sensation

The detection of physical stimuli in the environment, such as light waves, sound waves, pressure, or chemical molecules

Sound shadow

The difference in sound intensity due to head blocking/deflecting some of the sound waves

Gustation

The sensation of taste. The stimuli are contained in various foods we eat

taste buds

The sensory receptors for gustation that are located deep within porous structures on the tongue. There are five basic types of taste buds. -Each receptor is most sensitive to one particular taste and less sensitive to the other types of taste -5 basic types of taste: sweet, salty, sour, bitter, and umami

Pacinian corpuscles

The sensory receptors for touch located under the skin; theses sensory receptors respond to pressure and vibrations applied to the surface of the skin. They are located in the dermis (deep skin) and have large receptive fields

Interaural intensity difference

The slight difference in sound volume as it reaches one ear compared to the other (sounds slightly more intense in nearer ear)

Phase difference

The slight difference in the degree the sound wave is moving through its wave when it reaches one ear compared to the other

Depth cues

We get more sophisticated information when using both eyes (binocular cues) instead of just one eye (monocular cues) -Left and right eyes cover slightly different visual fields, and the images from the left & right eyes are slightly different (Binocular disparity)

magnocellular pathway

a visual pathway for peripheral vision and low spatial resolution images from the retina

olfactory hallucinations

smelling odors that are not really present, such as smoke or coffee

gustatory hallucinations

tasting something that isn't there, like metal or spoiled milk

Vestibular system

three semicircular canals that provide the sense of balance, located in the inner ear and connected to the brain by a nerve--damage can make even the simplest movements nearly impossible -Adequate stimuli include the position and movement of the head