Cognition Ch. 3

Sensation, Perception and Attention

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Modeling the Perceptual System

Our brains must convert physical energy to internal codingThis broad processes involves subprocesses:

The ability to perceive and store informationThe ability to translate that information into codeThe ability to derive meaning and utility from that codeThe ability to reproduce the original information

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Sensation to Perception

Sensation involves the detection of physical energyPerception involves higher-order cognition that “organizes” this energy

Be careful not to draw too solid a boundary between the two…

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Vision - Structure

Retinal stimulation creates a chain reactionRods and cones, ganglion cellsLateral geniculate nucleus (LGN)Visual cortex

The image is “disassembled” into its component parts (features)Reconstructed with interpretations installed

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The Marriage of Sensation and Perception

Illusions are good examples of this dynamicExamples

Muller-LyerFigure-groundPerceptual setsSignal detection

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From “Out There” to “In Here”

Perceptual span – how much we can experience at a brief exposure

Utilizes a sensory store to hold this information, but only brieflyEarly studies 4-5 letters was capacity, based on brief presentation followed by oral reportsEarly studies built foundation for “box” models of cognition

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Iconic Storage

Sperling what if some data is lost from the iconic store while the participant is reporting other data?

50 ms presentation of letter lists (3x3 matrix)Immediately following – one of three tones linked to rowsThe letters were recalled at close to 100% accuracyCaveat tone delay reduced recall

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Memory for Sounds

Moray et al (1965)Four speakers presenting messages simultaneouslyLetter strings presented through 2-4 channelsLights were used as cues for recall

Darwin et al (1972)Auditory analog to the Sperling studiesLeft ear, right ear, both ears – visual cue (stimulus position on screen)

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Attention

The concentration of mental effort on sensory or mental eventsFive major aspects

Processing capacity/selective attentionLevels of arousalAttention controlConsciousnessCognitive neuroscience

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Capacity and Selective Attention

Capacity – ability of the cognitive architecture to handle incoming dataAttention – concentration of cognitive energy on specific aspects of the environment

Attention is selective some stimuli are chosen, others are ignoredThe “bottleneck” metaphor

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Experimental Evidence

Cherry (1953, 1966) – shadowing techniqueMoray (1959) – cocktail party effectsLessons about selection

We prefer single streams of dataSome unattended information may “leak” throughRepeating information as presented may not translate into encoding that information

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Modeling Selective Attention

Broadbent (1958) – filter theory (Fig 3.10) -- capacity restricted by cognitive architecture

Data enters a short term storeA selective filter attends to the data based on its featuresData moves through channel to begin a closed-loop control function

Moderated by past probabilities

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Modeling Selective Attention

Treisman (1964) – attenuation model – attention is a function of activation thresholds

All data is sent to the attentional channelFiltered not by characteristics but by perceived importanceFilter reduces S/N ratio to produce the conscious realization of inattention

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Visual Attention

Serial v. parallel visual search (Treisman, 1988)Initial preattentive process that detects basic features of the environmentLate v. early filter theoriesLate filter or rapid trace decay?

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Automatic Processing

With practice, behaviors require less effortful attention to be producedConsiderable practice is required – some say 10 years or moreThree characteristics

Occurs without intention“Concealed” from consciousnessConsumes few cognitive resources