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. Percent Responding IntromissionExtromission 1 st graders 54%49% 3 rd graders 60%70% 5 th graders 31%51% College students 88%33% Our Class 22.5%67.5%

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 The Stimulus is… Your decision – You say the stimulus is… PresentAbsent Present (liberal) HitFalse Alarm Absent (conservative) MissCorrect Rejection

10. Cool Aspects of Perception Harold and the Purple Crayon http://www.hbofamily.co m/programs/jam/harold. html http://www.hbofamily.co m/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) Sensory Memory Meaningful processing Response Sensory Memory Meaningful processing Response Sensory Memory Meaningful processing Response x x x x Early Late

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 Information Sensation Perception Attention