sensation and perception Flashcards
define attention
the ability to preferentially process some parts of a stimulus at the expense of processing other stimuli
what are the eye movements between fixations called
saccades
what is attentional capture
how you first fixate on notable or important parts of a scene (scalience)
what directs attnetion
initially salience, but then our expectations and goals
what is the binding probelm
the issue of how an objects individual features, such as a colour and shape, are combined to create a coherent percept
what does feature integration theory state
the binding problem is solved by attending to only one location in a scene at a time
what is an illusory conjuction
where the features of 2 objects are incorrectly bound into one object
what is Balint’s syndrome
a condition resulting from damage to the parietal lobe, leading to a difficulty in focussing attention on a single object
what is a conjuction search
when the target object differs from its distractors only by its particular combination of features, not the individual features themselves - attention needs to be applied to each object in turn to determine whether the attended object is the target
what is structuralism
a theory proposed by Edward Titchener, claiming that sensations and perceptions are distinguished, and that sensations bind to form perceptions
what is gestaltism
the theory that conscious awareness can have characteristics not present in any of the elementary sensations (we can make stuff up)
two pieces of evidence for gestaltism
apparent motion (where two stationary dots in different positions alternatively flashed appear to be moving) as the observers doesnt actually see the objects moving - they just perceive this. Illusory contours (contours seen in placed where there are actually no physical contours) as the observers fills in the gaps themselves
what are 7 principles that govern grouping
good continuation (aligned contours are grouped), pragnaz (meaning “good figure”. Groupings occur to make the resultant figure as simple as possible). Similarity (the more similar objects are, the more likely to be grouped together). Proximity, (the closer objects are, the more likely they will be grouped). Common fate (things that are moving in the same way are grouped together). Common region (elements within the same region of space tend to group together). Uniform connectedness (connected regions with the same visual characteristics tend to group together)
4 principles that allow the figure of a scene to be percieved)
if the object is in front of the rest of the image , at the bottom of the image, convex or recognisable (based on expectations of what we think something should look like)
how much time must a scene be presented to get a gist of the scene
around 27ms. with 250 ms required for accurate perception
what part of the brain is associated with perceiving motion
the medial temporal area
what is akinetopsia
a condition, resulting from disease or trauma to the middle temporal lobe, causing difficulty perceiving motion
what are motion aftereffects
our photoreceptors can habituate to an image of constant motion so that when this stops, we may continue to perceive some form of motion
what is induced motion
when a moving background causes a stationary object to appear to move
the aperture problem?
when a moving object is partially obscured (viewed through an aperture), this can change how its motion is perceived
what is visible light
electromagnetic radiation with wavelengths between 400 and 700 nm
what is the colour white
a mixture of all the wavelengths of the visible spectrum
what are the 2 photoreceptors found on the retina
rods and cones
difference between rods and cones
rods cannot distinguish between colours and are only active at low light levels, while cones are active in normal light conditions and can perceive between colours
what are the 3 types of cones and what do they see
s cones (small) - blue, m cones (medium) - green and L cones (large) - red
what happens when an optimal wavelength is received by a cone
it becomes “excited”, and fires electrical signals called spikes up the optic nerve
what are metamers
objects that are made up of physically different wavelengths but appear to have the same colour
what is monochromatism
where a person has no functioning cones and therefore are truly colour blind (only able to see black and white). They are also very sensitive to light
what is dichromatism
where a person is lacking one of the three types of cones
what is unilateral dichromatism
where a person has normal trichromatic vision in one eye and dichromatic vision in the other
if you were to mix red and green light what would you get
yellow
if you were to mix blue and yellow light?
white light, as it is light that contains blue, red and green
what do protanopes lack
l cones
what do deuteranopes lack
m cones
what do tritanopes lack
s cones
what are the three colour opponent channels
red-green, yellow-blue and white-black
evidence for colour opponent channels
afterimages - when viewing a stimulus of one colour, the opponent colour percept will be supressed, however, our cones will habituate to this constant colour and become less sensitive to the stimulus. Therefore when a white stimulus is then shown, the opponent cones will respond more strongly (as they have not habituated) and you will therefore perceive this colour)
the fact that some colour combinations are impossible ( you cant perceive a redish green or a blueish yellow
what is colour constancy
the fact that we can perceive the colour of an object, even if it is only being shown under one wavelength of light, and therefore reflecting this light. eg. a green sweater under red light will only reflect red light, but still appear green
what is colour constancy
the fact that we can perceive the colour of an object, even if it is only being shown under one wavelength of light, and therefore reflecting this light. eg. a green sweater under red light will only reflect red light, but still appear green
how is colour constancy acheived
if an entire scene is under one colour of light eg. red, we habituate to this colour so that everything will appear greener or bluer than it otherwise would. We can also discount the illuminant, meaning that our brain can lear to determine, for example, that an object in a yellow scene that appears grey must actually be blue.
3 types of depth perception cues
oculormotor (the ability to sense the state and position of our eyes), monocular (one eye) and binocular (both eyes)
what are the 2 main oculomotor cues
binocular convergence and accomodation
what is binocular convergence
when an object is close, our eyes will converge to see it. The body can use the distance between the lines of sight of our eyes to determine the distance of the object.
what is accomodation
our lens changes to look at objects of different distances. A thinner lends is better able to see objects far away while a thick lens is used for closer objects. Our brain use this change in lens shape to determine distance
what are the 3 main monocular cues
pictorial, accomodation and motion based cues
what are the 7 pictorial cues
occlusion (if something is behind another object than it must be further away), relative height (a subject that is higher up in a scene appears further away), relative size, perspective convergence (2 parallel lines that appear to be converging indicate that they are getting further away), atmospheric perspective (as an object gets further way, the intensity of colour fades and there is less contrast between light and dark colours) , texture gradient (closer objects appear more detailed) and shadows
2 motion based cues (monocular)
deletion and accretion (when moving, objects will disappear behind others and then reappear, indicating that they are further away) and motion parallax (objects that are closer will appear to move faster than those that are further away)
what is retinal disparity
a binocular cue, the relative position between 2 objects on the retinal image, and the difference between these in each eye
what is the correspondence problem
if there are multiple identical objects in a scene, it can be hard to figure out which images in the left image should be associated with which images in the right - the correspondence problem
what 2 factors determine the percieved size of an object
angular size (on the retina) and its perceived depth
what did Holway and Boring investigate in 1941
they determined how depth cues influence size judgement. An observer would sit at the intersection of 2 corridors containing a circle at the end of each and with a range of provided depth cues (binocular disparity, motion parallax and shadows), were made to estimate the size of the object - there more depth cues, the more accurate their guesses
what is the ames room
a room where the design of the back wall interferes with the observers depth perception, making it seem like a straight wall. Therefore when 2 people are standing in 2 different corners of the room, their distance from the observer, and therefore size, is perceived wrong.
what does sound mean
can refer to both the physical phenomenon (pressure waves) and the perceptual phenomenon of actually hearing this sound
what is a pure tone
when the change in air pressure occurs in the shape of a sine wave
what causes a higher pitch (for pure tones)
a higher frequency of the wave
what does hertz mean
the amount of oscillations (periods/repeats) per second
what affects the loundness of a sound
amplitude of the waves
what is amplitude measured in
decibels
what is a complex tone
the addition of 2 or more pure tones to form a non-sine graph
what is perceptual loudness measured in
phons
what determines the pitch of a complex tone
the fundamental frequency (if a tone is composed of 3 tones, 200 400 and 600, the fundamental frequency is 200 as all the other frequencies are multiples of 200). Even if the fundamental tone itself is absent, the tone will sound like the fundamental frequency as all the other harmonics are multiples
what is timbre
the difference between the sounds of 2 sounds at the same pitch (a piano and guitar playing the same note will sound different). This occurs because while they may play the same fundamental frequency, they will play different harmonics of this frequency
what does it mean if 2 pitches have the same chroma
correspond to the same letter note - multiples of the same frequency
what are sound wave forms that dont repeat called
aperiodic
2 main dypes of auditory localisation cues
binaural (one ear) and monaural (both ears)
2 binaural cues
inter-aural time difference (a sound coming from the left will reach the left ear first) and inter-aural level difference (a sound coming from the left will be louder in the left ear than the right)
4 factors that determine the quality of architectural acoustics
reverberation time (the time it takes for a sound to decrease by 60 dB), intimacy time (the difference between when the direct sound arrives and the first indirect sound arrives), bass ratio (the ratio of low frequencies to middle/high frequencies) and spaciousness factor (the ratio of indirect sound to total sound)
