Cognitive Psychology Chapter 3
Visual Consciousness • Transduction of the visible spectrum (400 nm to 700 nm) of electromagnetic radiation. • Crossing of the visual pathways from retina to primary visual. Left visual field represented in right hemisphere.
Visual Consciousness • A critical periods for cortical development in cats show that primary visual cortex is necessary for visual consciousness. • Blindsight in humans: Damage to primary visual cortex eliminates visual consciousness but a second pathway allows accurate discrimination.
Types of Agnosia • Apperceptive Agnosia: object recognition fails because of difficulties in identifying the visual features of a perceptual category. • Associative agnosia: object recognition fails because of difficulties in identifying the functional features that define a semantic category.
Pattern Recognition • Refers to the step between the transduction and perception of a stimulus in the environment and its categorization as a meaningful object. • Agnosia—failure of pattern recognition caused by brain lesions.
Top-down vs. Bottom-up Processes • Organized knowledge representations called schemas direct exploration of objects and events in the environment. • Conceptually-driven processes provide expectations from the top-down. • Data-driven processes sample features from the bottom-up.
Word Superiority Effect • WORK vs. ORWK vs. K • Surprisingly, a single letter (K) is recognized faster in the context of a whole word (WORK) than when presented as an isolated letter. A nonword (ORWK) doesn’t provide this top-down advantage.
How are objects represented? • Distinctive feature lists may suffice for printed letters (Z is detected faster here OQBZPD than here TLKZMV). • But the structural relations among features are often as important as the features themselves.
Face Perception • Holistic vs. Analytic Processing • Faces are unique in that holistic processing is much stronger than analytic processing for them as compared with other objects.
Speech Recognition • Phonological segments that signal meaning (phonemes) unfold at 12/s or more. Fast, effortless processing of 40,000 bits/s implies a speech module. • The structural relations among phonemes—the context in which a phoneme occurs—is critical to recognition.
Why context is important? • Co-articulation: Each segment of speech provides clues about more than one phoneme. That is, multiple phonemes are articulated at the same time.
Why context is important? • Co-articulation: Each segment of speech provides clues about more than one phoneme. • Phonemes lack invariant distinctive features
Top Down Processing • Phonological segments are continuous in speech. Pauses heard are often illusions constructed by imposing phonemes from the top. • Subtle variations are ignored unless they fall at phoneme boundaries (categorical speech perception).