Perception and Sensory Memory Processes

Object Agnosia

• Patients cannot recognize shapes but can recognize the shape itself.
• Patients cannot recognize the same objects in different perspectives (e.g., roses or red dots).

Bottom-Up Processing

• Process where physical stimuli influence perception.
• Starts from transducers and goes up the visual process.

Top-Down Processing

• Process where existing knowledge influences perception.

Recognition

• Ability to match a presented item with an item in memory.

Representation

• Storage and/or reconstruction of information in memory.

Grouping

• Grouping together things that look alike.

Segregation

• Separating objects that look similar.

Figure-Ground Organization

• Determining what are objects and what is the background.

Law of Good Continuation

• Perceiving one thing behind another when an object continues.

Law of Proximity

• Things close to each other are seen as part of the same group (e.g., AJC QWE PKX).

Law of Similarity

• Similarity in size, color, or orientation.

Common Region

• Dots being circled together are seen as a group.

Connectedness

• Circles connected by lines are thought to go together.

Law of Common Fate

• Visual elements moving in the same direction are perceived as belonging together.

Perceptual Interpolation

• Detecting edges using V1 detectors.

Edge Perception

• Edges carry meaning; Y/Arrow indicates a corner, T indicates occlusion.
• Angles are also meaningful for good continuation.

Illusory Contours

• Perceived edges or lines that the brain constructs in the absence of actual physical boundaries (e.g., Pacman shape turned into a triangle or a 3D square).

Bottom-Up Driven

• Stimulus-driven (e.g., seeing a capital A or H).

Top-Down Driven

• Experience-based; knowledge shapes perception.

Geons

• Basic units of objects.
• Recognition by components; we recognize an object by the relation of its geons.

Viewpoint Invariance

• Vantage point doesn't matter for recognition.

Template Theories

• Point-by-point comparison to a stored "average or ideal" representation.

Problems with Template Theories

• Larger demands on memory.
• Vantage point matters for recognizing objects.
• Can't explain novel objects.

Brain Area for Representation of Shapes (Color)

• V4.

Location of Object Perception

• Inferotemporal (IT) area, which is responsible for complex visual processing.

Fusiform Face Area (FFA)

• Differentiates faces from one another.

Occipital Face Area (OFA)

• Helps determine if something looks like a face.

Prosopagnosia

• Lack of knowledge of faces. Individuals would not be able to identify a friend's face from a stranger's, or recognize animals.

The Grill-Spector Experiment

• FFA shows selective response to seeing familiar faces; potentially related to visual expertise (cars, birds).

Parahippocampal Place Area (PPA)

• Scene recognition.

Topographic Agnosia

• Deficit in recognizing spatial landscapes.

Extrastriate Body Area

• Body parts (not faces).

The Results of Quiroga - Grandma Cell

• Cells in the medial temporal lobe respond to a particular person or landmark from different angles and in different contexts.
• Suggests that we have certain cells that respond to specific landmarks or people.

The Face Inversion Effect

• Face processing breaks down when looking at a face upside down because we are not used to seeing faces in that arrangement.
• We are not doing a holistic process when faces are inverted upside down.

Object Agnosia

• A failure to recognize objects despite being able to see them.

Prosopagnosia

• Inability to recognize faces.

Double Dissociation

• People with prosopagnosia can't identify faces but can understand objects.
• People with object agnosia can't understand objects but can understand faces.

Capgrass Syndrome

• "Label" recognition intact but "emotional" recognition missing.
• Able to recognize faces but not the emotions attached to those faces.

Accidental Viewpoints

• Viewing scenes from a specific vantage point can trick our perceptual system briefly.
• We actively reconstruct and make sense of these images (e.g., holding the leaning tower or holding the sun).

Heterochromatic Light

• Any light source that has multiple wavelengths, able to measure.

Monochromatic Light

• Only produces very specific wavelengths (e.g., lasers).

Spectral Reflectance

• What is absorbed and reflected by a surface determines the color of the object.
• What wavelengths an object will absorb and reflect back into the environment.

Achromatic Lightness

• Amount of light reflected by the surface.
• The more a surface reflects, the more white it looks; the darker it looks, the less light it reflects.

Hue (Quality)

• Rainbow.

Saturation

• How intense a color is.

Brightness

• How much light is reflected back; amount of light coming out.

Additive Color Mixing (Mixing Lights)

• Light from light sources that has to be on the line in order to be a possibility of a color (e.g., yellow and blue gets white).

Non-Spectral Hues

• Colors not seen in the rainbow.

Relative Hues

• Brown does not exist in additive color mixing and is sensitive to the source of light.

Pointillism

• Small dots of paint that, from a distance, blend together through additive mixing.

Subtractive Color Mixing

• Color absorbs other parts of the color spectrum and then reflects light.
• For example, colors near blue will reflect off, and colors that are not close to blue are absorbed.

Subtractive color Mixing Example

• When blue and yellow are mixed, green is not absorbed, so that is the only color that is reflected.

Metamer

• Once a good match of color is made, it's called a metamer; you cannot tell which one was already made and which one was created.

Metameric Matching

• Different wavelengths produce the same color experience, example yellow.

S Cone

• Short blue wavelength.

M Cone

• Medium yellow/green wavelength.

L Cone

• Long red wavelength.

The Response of Cones to a 500-nm Light

• Blue cones respond weakly, green cones respond very strongly, red cones in the middle.

Univariance

• The principle whereby any single cone system is colorblind, in the sense that different combinations of wavelength and intensity can result in the same response from the cone system.

The Trichromatic Theory of Color Vision

• Three cone systems in our retinae.

Herings Model of Opponent Processes

• Red-green, blue-yellow, white-black.
• Organizing colors by pairs that do not mix (opponents).

Afterimages

• Seeing opponents of color after staring at them for a while.
• When looking at black light after, the after image disappears.

Hue Cancellation Experiments

• Start with yellow light.
• Goal: turn yellow light into pure white light by adding blue.
• At some point, the light has no color (no hue).
• Opponent color combinations destroy the chromaticity in light.

Color Opponent Cells

• Colors we see, not wavelengths.

Cone Opponent Cells in LGN

• M - L cones; Y - B cones - V1.

Double Opponent Cells

• Sharpen color boundaries, color patterns, but not continuous colors.

Color Processing in the Brain

• Cells in V4 respond to perceived color, not the wavelengths that stimulate the eye.

Rod Monochromacy

• Individuals that only have rods cannot see color.

Cone Monochromacy

• Individuals that have rods but only one cone cannot experience color.

Dichromacy

• Have retinas that have rods and two types of cones, with specific deficits of colors they cannot see.
• The majority of species are dichromats.

Tritanopia

• No S cone, and lack green and yellow.

Protanopia

• No L cone, and lack green and red.

Deuteranopia

• No M cone, and lack green and red.

Cortical Achromatopsia

• Loss of color vision because of damage to the occipital lobe.

Common Color Errors

• Brown-blue look alike.
• Red-green are difficult to tell apart.
• Yellow-orange look alike.

Yellow Surfaces

• Color reflected and coded along the yellow-blue channel.

Red and Green Surfaces

• Surfaces reflect a little bit of yellow light; however, red and green cannot be coded by the yellow channel.

Blue Surfaces

• Blue is the opponent color of yellow, so the yellow light will remove or kill the blue.
• Blue surfaces reflect only very little light, so they will look very dark.

Brown Surfaces

• Don't reflect a lot of light in general, so they will look dark.

Orange Surface

• Yellow + red.
• Yellow is reflected, but red is not and cannot be coded by the yellow channel.

Color Constancy

• Ability to perceive the color of an object despite changes in illumination.

Lightness Constancy

• Ability to perceive the relative reflectance of objects despite changes in illumination.

Color and Visual Acuity

• Cones clustered together around fovea and are in midget system, which gives us spatial acuity.

Synesthesia

• Accidental association of two precepts, with one perception eliciting a secondary perception (two or more).
• Stimulation of one sensory or cognitive pathway leads to automatic, involuntary, experiences in a second sensory or cognitive pathway.

Retina and motion

• Motion thresholds is seen in the retina.

How to Determine How Slow and Fast an Object Is

• The farther away an object, the slower it looks. Stationary to us = fast moving.

Real Motion

• Motion in the world created by continual change in the position of an object relative to the frame of reference.

Apparent Motion

• Sequence of still images.

Correspondence Problem

• How the visual system correctly perceives the overall motion of objects.
• Local information; sets of hypotheses are made by each aperture.
• Overall motion direction = hypotheses that are shared by all apertures.

Motion detection in the eye

• In the retina, we can determine approximate speed of moving object with Point 1 and point 2 and time 1 time 2.

Reichardt Detectors

• Will only fire if signals are received from both neurons.
• If delay is too long or too short, motion neurons won't respond.
• If object moves from right to left, neurons will also not activate.

Corollary Discharge Theory

• Motor system tells the eyes to move and sends a copy to the brain.
• When the brain/eyes are stationary, the image appears on the opposite side of the retina.
• When eyes are following the object, the object is stationary with the retina.

Saccades

• Very quick eye movements; less than $15 ms$, we make 3 saccades each second.

Smooth Pursuit Eye Movements

• Voluntary movements used to track moving objects (e.g., tracking a flying eagle or a tennis ball moving).

Saccadic Suppression

• Refers to the strong reduction in visual processing during the execution of a saccade.

MT (V5)

• Sensitive to direction and speed of motion but not in terms of detail.

Akinetopsia (Motion Blindness)

• Able to tell details of objects but not sense motion.

Weigelt (2013) Results

• Confirmed that motion is coded in MT.
• When paying attention to motion, there is bigger activation.

Affordance

• Information in the visual world that specifies how that information can be used (e.g., a chair has a flat surface, so we note that we can sit on it).

Optic Flow

• Movement of objects, surfaces, and edges due to the motion that is being perceived.
• How close you are to an object and how fast that distance is closing.

Gradient of Flow

• The faster you are, the more the gradient accelerates and vice versa.

Focus of Expansion

• Point we are looking at stays still with different fixation points.

Lateral Intraparietal (LIP) Area

• located in the Parietal lobe.

Medial Intraparietal (MIP) Area

• Reaching movements.
• Helps transform visual information of location to objects into how we should move our arms and how much muscle is required.

Anterior (AIP) Area

• Manipulating and grasping.
• More precise actions; processes shape size and orientation of an object and how to grab it.

Cue Approach to Depth Perception

• Our visual systems must re-create the 3D world using an essentially flat, 2D retina.

Oculomotor Cues

• Accommodation and vergence.

Accommodation

• Process of adjusting the lens of the eye so that one can see both near and far objects.
• To see near, the lens becomes thick; to see far, the lens becomes thin.

Vergence

• Bringing eyes together to focus on an object.

Occlusion

• Happens when one object partially hides or obstructs the view of a second object.

Relative Height

• Objects closer to the horizon are seen as more distant.

Relative Size

• The more distant the object, the smaller the image will be on the retina.

Familiar Size

• We judge distance based on existing knowledge of the size of objects.

Linear Perspective

• Pictorial depth cue that arises from the fact that parallel lines appear to converge as they recede into the distance.

Texture Gradients

• Textures become finer as they recede in the distance.

Atmospheric Perspective

• Objects in the distance appear blurred and tinged with blue.

Shadows and Shading

• An object in front of its shadow, and the angle of the shadow can provide some information about how far the object is in front of the background.

Motion Parallax

• Cue that arises from the motion of a person in the environment.
• Faster-moving objects are closer to us; slower-moving objects are farther away.

Deletion

• Deletion is the gradual occlusion of a moving object as it passes behind another.

Accretion

• Accretion is the gradual reappearance of a moving object as it emerges from behind another object.

Optic Flow

• Motion depth cue that refers to the relative motions of objects as a person moves forward or backward.

Stereopsis

• Sense of depth that we perceive from the visual system's processing of the comparison of the two different images from each retina.

Binocular Disparity

• Images on the left and right vary on certain degrees.

Three-Dimensional Movies

• Provide two different images to each lens from both sides of glasses.

Horopter

• Region in space where the two images from an object fall on corresponding locations on the two retinae (not inside eyes, out in space).
• Corresponding points are part of our eyes and forms wherever you are looking at.
• Fixation point.
• Points along the horopter have zero disparity (i.e., retinal images fall along corresponding points).

Corresponding Points

• If the distance is exactly the same from both eyes, the image falls in the corresponding points.

Panum's Area of Fusion

• Region of small disparity around the horopter where the two images can be fused into a single perception.

Diplopia

• Results from the images of an object having too much disparity to lead to fusion.

Crossed Disparity

• Refers to the direction of disparity for objects in front of the horopter (the image in the left eye as to the right of the image of the object in the right eye).

Uncrossed Disparity

• Refers to the direction of disparity for objects that are behind the horopter (image of the object in the left eye is to the left of the image of the object of the right eye).

Stereograms

• 2D image that is turned into a 3D image when viewed at a specific angle.

Anaglyph

• Blurry pictures that can be seen clear by glasses that have filters on the lens.

Size Perception

• Size-distance invariance.

Visual Angle

• The angle of an object relative to one's eye.

Size Constancy

• Perception of an object as having a fixed size, despite the change in the size of the visual angle that accompanies the change in distance.

Ponzo Illusion

• Two objects that have the same size on the retina but make one object standing farther away look bigger.

Muller-Lyer Illusion

• Line with arrows up and down make one line look bigger than the other.

Ebbinghaus Illusion

• Same object can look smaller or bigger depending on surrounding objects.