Psychology 1100- Chapter 4 (Sensations and Perceptions)

What are sensation and perception?

Sensation: simple stimulation of a sense organ, such as registration of light, sound, pressure, smell, or taste

Perception: the organization, identification, and interpretation of a sensation in order to form a mental representation

Through which process do sensory receptors communicate with the brain?

Transduction: occurring when sense receptors convert physical signals from the environment into neural signals that are sent to the CNS

Ex. vision-reflected light provides eyes with info

hearing-vibrations cause changes in air pressure that move through space to the ear

touch-pressure of surface against skin signals shape, texture etc

taste and smell-molecules dispersed in air dissolve in saliva

What is sensory adaption?

Sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current (unchancing) conditions

Ex. Waking into a bakery and the smell being overwhelming, but fading after a few minutes

What is psychophysics?

Methods that systematically relate the physical characteristics of a stimulus to an observer’s perception

Ex. in a simple psychophysics experiment, researchers might ask people to decide whether or not they see a faint spot of light, with the intensity of the light being changed systematically and the responses recorded as a function of intensity

What is the simplest quantitative measurement in psychophysics?

Absolute threshold: minimal intensity needed to just barely detect a stimulus in 50% of trials

What is the absolute threshold useful for assessing?

Sensitivity: how responsive we are to faint stimuli

Acuity: how well we can distinguish two very similar stimuli

Just noticeable difference (JND): minimal change in a stimulus (loudness or brightness) that can just barely be detected

What is the approach signal detection theory in psychophysics?

The response to a stimulus depends both on a person’s sensitivity to the stimulus in the presence of noise and on a person decision criterion

What are characteristics of visible light?

Wavelengths: height and distance between their peaks

Length: distance, determines hue (colour)

Amplitude: intensity (height of peaks), determines brightness

Purity: degree to which light source is emitting one wavelength or a mixture, influences how colour is perceived

What are parts of the eyes an their functions?

Cornea: clear, smooth outer tissue, bends light waves and sends to pupil

Pupil: hole in coloured part of the eye

Iris: translucent, circular muscle that controls pupil size and hence the amount of light that can enter the eye

retina: layer of light-sensitive tissue lining back of the eyeball. Muscle changes shape to focus objects at different distances (flatter for far away, rounder for near)

Fovea: area of the retina where vision is the clearest and there are no rods at all

Optic nerve: leaves ete through hole in the retina

What is accomodation?

The process whereby the eye maintains a clear image on the retina

What happens if the eyeball is too long or too short?

Too long: imaged focused in front of the retina, leading to nearsightedness (myopia)

Too short: images focused behind the retina, leading to farsightedness (hyperopia)

What types of cells does the retina contain to be able to make light into pictures?

Photoreceptor cells called cones and rods

Cones: detect colour, operate under normal daylight conditions, allow us to focus on fine detail

Rods: become active only under low-light conditions, night vision (more sensitive than cones)

What does the hole from the optic nerve create?

It creates a blind spot, a location in the visual field that produces no sensation of the retina

What is area V1?

The part of the occipital lobe that contains the primary visual cortex

What two visual streams are there?

Ventral (lower): travels across occipital lobe to lower temporal lobe levels, areas that represent an object’s shape and identity (referred to as the “what” pathway)

Dorsal (upper): travels from occipital lobe to parietal lobes + middle and upper temporal lobe levels), areas where object is identified and how it moves (dubbed the “where” pathway)

What is the binding problem?

How the brain links features together so that we see unified objects in our visual world rather than free-floating or miscombined features

What is parallel processing?

The brain’s capacity yo perform multiple activities at the same time

What are illusory conjunctions and how do they occur?

Illusory conjunctions: a perceptual mistake whereby the brain incorrectly combines features from multiple objects

Explain via the feature-integration theory: holds that focused attention is not required to detect the individual features that make up a stimulus, but is required to bind them together

What is perceptual constancy?

The idea that even as aspects of sensory signals change, perception remains constant

Ex. recognizing our friend and still notice changes in hair colour or style, but constancy acts such that we don’t notice the object has changed

What is perceptual organization its rules?

The process of grouping and segregating features to create whole objects organized in meaningful ways

Simplicity: when confronted with multiple interpretations of an object, visual system tends to select the simplest one

Closure: tendency to fill in missing elements of a visual scene

Continuity: edges or contours that have same orientation are grouped together

Similarity: regions that are similar in colour, lightness, shape are perceived to belong to the same object

Proximity: objects close together are grouped together

Common fate: elects of a visual image that move together are perceived as parts of a single moving object

What are monocular depth cues and binocular disparity?

Monocular depth cues: aspects of a scene that yield info about depth when viewed with inly one eye

Binocular: difference in the retinal images of the two eyes that provide info about depth

What does our sense of hearing depend on?

Sound waves: changes in air pressure unfolding over time(vibration of vocal cords, resonance of a guitar string)

What are the parts of the ear?

Outer ear: collects sound waves and funnels them toward the middle ear

Middle ear: transmits vibrations to inner ear

Inner ear: embedded in the skill, sound waves transduced into neural impulses

Outer ear parts

Pinna: visible part on outside of head

Auditory canal

Eardrum: air tight flap of skin that vibrates in response to sound waves

Middle ear parts

Contains the ossicles, shaped as a hammer, anvil and stirrup, fit together into a lever that mechanically transmits and amplifies vibrations to the inner ear