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 Necker cube.

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