Perception and Attention Advanced Cognitive Psychology PSY 421

Perception and Attention Advanced Cognitive Psychology PSY 421, Fall 2004

Overview n Misperception – An Example n Sensation n Perception n Attention

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

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

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

Sensations n Physiological reaction to encountering information (system is stimulated) n 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. n Sensory systems respond consistently; our experiences (our perceptions) are different most of the time n Sensory information and “tools” n Visual system = light waves; fovea, receptive field, receptors (rods and cones), ganglion and bipolar cells n Auditory system = sound waves, frequency and intensity; pinna, tympanic membrane, bones of the middle ear, cochlea, hair cell receptors n Olfaction = odor molecules, hair cell receptors n Gustation = chemicals, papillae, taste buds n All systems have neural components that take the sensory “messages” to the brain

Perception n Registering information/stimuli and apply prior knowledge and experience to interpretation of that information n Processing of this information can happen in two ways: n n 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

Perception and Psychophysics n Reminder: Psychophysics involves studying the relationship between the physical aspects of the stimulus and how the stimulus is perceived n Thresholds – way of describing stimulus energy and how it impacts the detection of the stimulus n n 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 n Sensitivity – knowledge that a stimulus was perceived/detected n Response Bias – willingness to report that a stimulus was perceived/detected n Signal Detection Theory – both sensitivity and response bias characterize your perceptual experiences

The Box – Signal Detection Theory The Stimulus is… Your decision – You say the stimulus is… Present Absent Hit False Alarm Miss Correct Rejection (liberal) Absent (conservative)

Cool Aspects of Perception n Harold and the Purple Crayon n http: //www. hbofamily. co m/programs/jam/harold. html

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

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

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

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

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

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

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

Putting it all together n ns a tio n Perception Se A tio n tte Information