Perception and Attention

1. Perception and Attention Advanced Cognitive Psychology PSY 421, Fall 2004

2. Overview • Misperception – An Example • Sensation • Perception • Attention

3. (Mis)Understanding Visual Perception • Assignment – draw lines from the eye to the object and explain how the eye “sees” the object

4. Extramission Theory of Visual Perception • Jane E. Cottrell and Gerald A. Winer (multiple publications) • Extramission Theory = there are emanations from the eyes during the act of seeing • Intromission Theory = there is only input to the visual system and that this information alone allows people to see.

5. Sensation, Perception, and Attention • How the cognitive system “registers” information • Sensation = physiological process that occurs when information is encountered • Perception = psychological processes involved in the immediate organization and interpretation of sensations (influenced by our previous knowledge, expectations, and biases) • Attention = processes devoted to the monitoring of internal and external events, information, objects, etc.

6. Sensations • Physiological reaction to encountering information (system is stimulated) • Processes in which physical energy from the environment is transduced into neural responses that represent basic information about the stimulation received by the sensory receptors. • Sensory systems respond consistently; our experiences (our perceptions) are different most of the time • Sensory information and “tools” • Visual system = light waves; fovea, receptive field, receptors (rods and cones), ganglion and bipolar cells • Auditory system = sound waves, frequency and intensity; pinna, tympanic membrane, bones of the middle ear, cochlea, hair cell receptors • Olfaction = odor molecules, hair cell receptors • Gustation = chemicals, papillae, taste buds • All systems have neural components that take the sensory “messages” to the brain

7. Perception • Registering information/stimuli and apply prior knowledge and experience to interpretation of that information • Processing of this information can happen in two ways: • Bottom-up or Data-Driven Processing = flow of information from the stimulus to the brain (neural activity), to interpretation or identification • Top-Down or Conceptually-Driven Processing = processing starts with previous knowledge influencing what we see, hear, touch, taste, smell

8. Perception and Psychophysics • Reminder: Psychophysics involves studying the relationship between the physical aspects of the stimulus and how the stimulus is perceived • Thresholds – way of describing stimulus energy and how it impacts the detection of the stimulus • Absolute Threshold – amount of stimulus energy needed to detect the stimulus 50% of the time • Difference Threshold – amount of change in stimulus energy that is detectable 50% of the time • Sensitivity – knowledge that a stimulus was perceived/detected • Response Bias – willingness to report that a stimulus was perceived/detected • Signal Detection Theory – both sensitivity and response bias characterize your perceptual experiences

9. The Box – Signal Detection Theory

10. Cool Aspects of Perception • Harold and the Purple Crayon • http://www.hbofamily.com/programs/jam/harold.html

11. More Cool Aspects • McGurk Effect – visual influence on speech perception • Hear one syllable (ba) and see an image of someone pronouncing another syllable (ga) • When these are different, the sound hear is a combination of the two syllables (ba–da--ga) • Synethesia – input to one sensory system stimulates a reaction from another sensory system (e.g., pitch and color) • Subliminal Perception or Perception without Awareness

12. (PAY) Attention • Voluntary Control – we are in control of how we deal with incoming information • Limited Capacity – we cannot effectively attend to (monitor) all events occurring around us at the same time • Selective Attention • Divided Attention

13. Theories of Attention • Gateway Theories – attention is a filter • Dichotic listening tasks and speech shadowing • Early Selection Theories • Filter Model of Attention (Broadbent, 1958) • Opposing evidence • Cocktail Party Phenomenon • Treisman (1960) – perception vs. meaning • Attenuation Theory (Treisman, 1960) • Late Selection Theories

14. Gateway Theories of Attention • Early Selection • Message 1 (attended) • Message 2 (unattended) • Attenuation • Message 1 (attended) • Message 2 (unattended) • Late Selection • Message 1 (attended) • Message 2 (unattended) x Sensory Memory Meaningful processing Response x Sensory Memory Meaningful processing Response x Sensory Memory Meaningful processing Response x Late Early

15. Attention as Capacity • Attention is limited and must be allocated according to the demands of the situation • This is the idea of attentional “resources” • Is there one resource type; are there multiple types (perhaps based on modality)? • Issue regarding capacity – can we overload our attentional system? (i.e., run out of attentional resources)

16. Multimode Theory of Attention • Attention is flexible in that people can shift from early modes of attention (processing physical characteristics of stimuli) to late modes (processing meaning) • Johnston and Heinz (1978)

17. Automaticity • Automatic Processing = some activities require very little attention; usually the result of practice. • Examples: Stroop Effect and Visual Search Studies • Action slips = behaving in the absence of attention

18. Putting it all together Attention Perception Sensation Information