Week 8: The Visual World Flashcards
Seeing, Multi-Modal Perception
Electromagnetic Energy
Pulses of energy waves that can carry info from place to place
Wave-length
Distance between one wave peak ant the next wave peak
Visible Spectrum
the part of the electromagnetic spectrum that our eyes can detect (only the range from about 400 to 700 billionths of a meter
Cornea
A clear covering that protects the eye and begins to focus the incoming light
Pupil
A small opening in the centre of the eye
Iris
the coloured part of the eye that controls the size of the pupil by constricting or dilating in response to light intensity
Lens
A structure that focuses the incoming light on the retina
Retina
Cell layer in the back of the eye containing photoreceptors
Visual accomodation
the process of changing the curvature of the lens to keep the light entering the eye focused on the retina
Nearsighted
When the focus is in front of the retina
Farsighted
When the focus is behind the retina
Optic Nerve
A collection of millions of ganglion neurons that sends vast amounts of visual info via the thalamus, to the brain
Rods
Photoreceptors of the retina sensitive to low levels of light; located around the fovea
Cones
Photoreceptors of the retina sensitive to colour; located primarily in the fovea
Fovea
the central point of the retina
Blind spot
A hole in our vision that is created because there are no photoreceptor cells at the place where the optic nerve leaves the retina
Feature Detector Neurons
Specialized neurons, locate din the visual cortex, that respond to the strength, angles, shapes, edges, and movements of a visual stimulus
Hue
The shade of a colour
Trichromatic Colour Theory
The colour we see depends on the mix of the signals from the three types of cones
Colour Blindness
The inability to detect green and/or red colours
Opponent-process colour theory
Proposes that we analyze sensory info not in terms of three colours but rather in three sets of “opponent colours”: red-green, yellow-blue, and white-black
Gestalt
A meaningfully organized whole
“the whole is the sum of its parts”
Summary of Gestalt Principles of Form Perception
Figure and Ground - We structure input so that we always see a figure (image) against a ground (background).
Similarity - Stimuli that are similar to each other tend to be grouped together.
Proximity - We tend to group nearby figures together.
Continuity - We tend to perceive stimuli in smooth, continuous ways rather than in more discontinuous ways.
Closure - We tend to fill in gaps in an incomplete image to create a complete, whole object.
Visual Cliff
A mechanism that gives the perception of a dangerous drop-off, in which infants can be safely tested for their perception of death
Binocular Depth Cues
Messages from our bodies and the external environment that supply us with info about space and distance
Convergence
The inward turning of our eyes that is required to focus on objects that are less than about 50 feet away from us
Accommodation
Helps determine dpeth
Monocular Depth Cues that Help us Judge Depth at a Distance
Position - We tend to see objects higher up in our field of vision as farther away.
Relative size - Assuming that the objects in a scene are the same size, smaller objects are perceived as farther away.
Linear perspective - Parallel lines appear to converge at a distance.
Light and shadow - The eye receives more reflected light from objects that are closer to us. Normally, light comes from above, so darker images are in shadow.
Interposition - When one object overlaps another object, we view it as closer.
Aerial Perspective - Objects that appear hazy, or that are covered with smog or dust, appear farther away.
Beta Effect
Perception of motion that occurs when different images are presented next to each other in succession
Phi phenomenon
we perceive a sensation of motion caused by the appearance disappearance of objects that are near each other
Seeing - Key Take Aways
Vision is the process of detecting the electromagnetic energy that surrounds us. Only a small fraction of the electromagnetic spectrum is visible to humans.
The visual receptor cells on the retina detect shape, colour, motion, and depth.
Light enters the eye through the transparent cornea and passes through the pupil at the centre of the iris. The lens adjusts to focus the light on the retina, where it appears upside down and backward. Receptor cells on the retina are excited or inhibited by the light and send information to the visual cortex through the optic nerve.
The retina has two types of photoreceptor cells: rods, which detect brightness and respond to black and white, and cones, which respond to red, green, and blue. Colour blindness occurs when people lack function in the red- or green-sensitive cones.
Feature detector neurons in the visual cortex help us recognize objects, and some neurons respond selectively to faces and other body parts.
The Young-Helmholtz trichromatic colour theory proposes that colour perception is the result of the signals sent by the three types of cones, whereas the opponent-process colour theory proposes that we perceive colour as three sets of opponent colours: red-green, yellow-blue, and white-black.
The ability to perceive depth
occurs as the result of binocular and monocular depth cues.
Motion is perceived as a function of the size and brightness of objects. The beta effect and the phi phenomenon are examples of perceived motion.
Unimodial
Of or pertaining to a single sensory modality
Sensory Modalities
A type of sense; ex. vision/audition
Multimodial
Of or pertaining to multiple sensory modalities
Multimodal Perception
The effects that concurrent stimulation in more than one sensory modality has on the perception of events and objects in the world
Integrated
Process by which the perceptual system combines info arising from more than one modality
Superadditive effect of multisensory integration/multisensory enhancement
finding that repsonses to multimodal stimuli are typically greater than the sum o f the independent responses to each unimodal component if it were presented on its own
Unimodal components
the parts of a stimulus relevant to one sensory modality at a time
Principle of Inverse Effectiveness
The finding that, in general, for a multimodal stimulus, if the response to each unimodal component (On its own) is weak, then the opportunity for multisensory enhancement is very large; however if one component (by itself) is sufficient to evoke a strong response, then the effect on the response gained by simultaneously processing the other components of the stimulus will be relatively small
Multisensory Convergence Zones
Regions in the brain that receive input from multiple unimodal areas processing different sensory modalities
Receptive field
The portion of the world to which a neuron will respond if an appropriate stimulus is present there
Crossmodal receptive fields
A receptive field that can be stimulated by a stimulus from more than one sensory modality
Spatial principle of multisensory integration
the finding that the superadditive effects of multisensory integration are observed when the sources of stimulation are spaitally related to one another
Unimodal cortex
a region of the brain devoted to the processing of info from a single sensory modality
Primary auditory cortex
area of the cortex involve din processing auditory stimuli
Multimodal phenomena
effects that concern the binding of inputs from multiple sensory modalities
McGurk effect
An effect in which conflicting visual and auditory components of a speech stimulus result in an illusory perecpt
Double flash illusion
false perception of two visual flashes when a single flash is accompanied by two auditory beeps
The perception of collisions between two circles (called “balls”)
the tendency to perceive two circles as bouncing off each other if the moment of their contact is accompanied by an auditory stimulus
Rubber hand illusion
the false perception of a fake hand as belonging to a perceiver, due to multimodal sensory info
Crossmodal Phenomena
effects that concern the influence of the perception of one sensory modality on the perception of another
Primary visual cortex
Area of the cortex involved in processing visual stimuli
Crossmodal Stimuli
A stimulus with components in multiple sensory modalties that interact w each other
Monacular Depth Cues
Depth cues that help us perceive depth using only one eye
