MIND: The Cognitive Side of Mind and Brain

� “… the mind is not the brain, but what the brain does…” (Pinker, 1997)

COGNITIVE PSYCHOLOGY emerged late 1960s:

� The scientific study of higher mental processes, from perception and action through memory, language, thinking, and problem solving. These mental activities involve the processing of information.

COGNITIVE PSYCHOLOGY

� GOAL: To understand how the mind works

� METHODS: Based on scientific experimentation

� EXPLANATION: Focuses on the nature of mental representations and the processes that operate on them

INFORMATION PROCESSING METAPHOR:

� Both brain and computers process information

� Information (knowledge, representation, symbols) is independent of the physical medium

COGNITIVE SCIENCE: Interdisciplinary study of the mind emerged late 1970s� Cognitive Psychology� Artificial Intelligence� Neuroscience� Linguistics� Philosophy� Anthropology

NEUROSCIENCE

� GOAL: To understand how the brain works

� METHODS: Based on scientific experimentation

� EXPLANATION: Focuses on nervous system function and performance

Cognitive Psychology and Neuroscience Together

� Initially, interest, but little direct contact� Two sides of a coin; burning a candle at

both ends� Very difficult to map cognitive level of

explanation onto brain

� Today, the cumulative advances in our scientific knowledge and technology have opened new possibilities for collaboration.

Cognitive Psychology provides:

� Logical analysis of the mental structures and processes presumed to be involved in the performance of many tasks (task analysis).

� This analysis used to develop cognitive tasks to assess aspects of perception, attention, and memory.

� Models of mental structures and processes of human perception, attention, memory, etc. based on data obtained from solid experimental procedures

Cognitive Psychology and Neuroscience:

� 1990s: Neuroimaging studies demonstrate activation of specific brain areas when people perform classic cognitive tasks.

� 2000s: Some neuroimaging studies help distinguish between alternative theoretical accounts of cognitive performance.

COURSE OVERVIEW

� Visual Perception: We are visual animals

� Visual Attention: We select some, but not all, stimuli for processing

� Visual Awareness: We are conscious of some, but not all, experiences

PERCEPTION

� Ramachandran video: � Phantom limb, blind sight, unilateral

neglect, Capgras syndromes reveal that visual perception is not the same as sensation.

IMPOSSIBLE OBJECTS

� Objects to right initially look like coherent objects, but they are not physically possible.

� Vision does not simply register what is present. It actively constructs percepts

VISUAL PERCEPTION

� ACTIVE INTERPRETATION of sensory input

� “We perceive the world through the filter of our knowledge and experience”

Consider THIS ROOM from the perspective of:

� Our eyes� Pre-school child Moose� Moose

VISUAL PERCEPTION

� GOAL: To understand the 3D structure of the world around us by identifying:� What objects are out there � Where they are located � What they are doing

Recognizing Things

� Single Objects: � My mug in different places, orientations,

lighting conditions changes location, size.

� Letters & Words: � Type fonts, all other above variations.

� Faces: � Different views (frontal, side), all other

above variations

Three Levels of Perceptual Identification

� Superordinate: Fruit� Entry level: Apple� Subordinate: Granny Smith Apple

� Sensory input identified at the level appropriate for the task at hand: If we want to eat an apple, we identify the object as an apple, not as a fruit or a Granny Smith apple.

Stages of Processing: A Generic Symbolic Model

Stages of Processing

� Each stage (i.e., box) is a different level of processing.

� Two classes of processes:Bottom-up (data-driven, sensory-driven)Top-down (conceptually driven)

Dimensional analysis

� A large set of “detectors” operating in parallel to code edges, color, movement (covered in lectures on Chapters 1 and 2).

� Analyzers operate in parallel.

Figure Construction Mechanism

� Organizes the image by segmenting (parsing) it into parts and grouping the parts appropriately.

� How do we know which parts go together in the figure to the right?

Figure Construction Mechanism

� Organizes image by binding attributes together

� Gestalt Principles of Grouping

� Multiple glimpses, binocular disparity

� Shape from shading, depth from texture

Figure Construction Mechanism

� Organizes image by determining what is figure (that which we attend to) and what is ground.

� Ambiguous figures: two equally good figures constructed, as in the Neckercube.

Perceptual Representation and Comparison Mechanism

� Perceptual Representation: The organized percept, ready for identification.

� The perceptual representation is compared to our stored shape knowledge (i.e., shape representations) by the Comparison Mechanism.

Top-down Influences

� Local context and our expectations influence perception.

� We do not yet know how early in visual processing top-down influences of context operate.

Definitions� Bottom-up processing

(BU): The sequence of mental events is largely determined by the pattern of incoming information.

� Top-down processing (TD): The sequence of mental events is influenced by our knowledge and expectations.

� In perception:� processing initially

starts with sensation and BU processing.

� thereafter, BU and TD processing occur simultaneously.

VISUAL PERCEPTION

� GOAL: To understand the 3D structure of the world around us by identifying what objects are out there, where they are located, and what they are doing.

What’s next?

� Dr. Carolyn Harley completes coverage of Chapters 1 & 2� Chapter 1: Early Vision: Retina and

Retinal Ganglion Cells, LGN, Primary Visual Cortex

� Chapter 2: From Local to Global Image Recognition: Color, Motion, Image Segmentation, Two Cortical Systems