1. Sensation and Perception

2. True or False?
Advertisers are able to shape our buying habits through subliminal messages.
If we stare at a green square for a while and then look at a white sheet of paper, we see red.
Touching adjacent cold and pressure spots triggers a sense of wetness.
People who are born without the ability to feel pain may die by early adulthood.
Without their smells, a cold cup of coffee may be hard to distinguish from a glass of red wine.
Infants just learning to crawl do not perceive depth
Persons who have sight in only one eye are totally unable to gauge distances.
A person who is born blind but gains sight as an adult cannot recognize common shapes and forms.
If required to look through a pair of glasses that turns the world upside down, we soon adapt and coordinate our movements without difficulty.
Laboratory evidence indicates that some people do have ESP.

3. Sensation and Perception
Transformation of stimulus energy into a meaningful understanding
Each sense converts energy into awareness

4. Sensation
Detection and encoding of physical stimuli into neural signals
Occurs at sensory receptors
External stimuli correspond to sensory modalities
Light waves: ___________
Sound waves : ___________
Pressure, warmth, cold, pain : ___________
Chemical messengers : _________&__________
Body position and movement : _________&_________

5. Perception
Organization of sensory information into cognitive awareness environmental stimuli
Occurs in the cerebral cortex

6. Processing stimuli Bottom-up processing Top-down processing
Scientific explanation
Begins with receptors and works up to integration
Top-down processing
Understanding stimuli based on prior experience and expectations
The brain will rapidly interpret stimuli based on their “most likely” explanation

7. Thresholds of sensation
Absolute threshold
Minimum stimulation
needed to detect a
stimulus 50% of the time
Ex. Whisper
Difference threshold
Minimum difference between two stimuli that can be detected 50% of the time
Ex. Change in room temperature

8. Subliminal sensations
Sensations not strong enough to be perceived
May be processed sometimes
May result in understanding without conscious awareness
Useful persuasion method?

9. Sensory adaptation Diminished sensitivity to a continuous stimulus
Allows for focus on relevant stimuli

10. Vision
Stimulus: visible light
Wavelength
Intensity

11. Vision
Receptive organ: the eye

12. Photoreceptors
Rods
Cones

13. Visual pathway Optic nerve Optic chiasm Thalamus Primary visual cortex
Exits retina
Optic chiasm
Thalamus
Primary visual cortex

14. Processing visual stimuli
Feature detectors in the primary visual cortex respond to specific features in parallel
Form
Movement
Depth
Color

15. Perception of visual stimuli
Perception occurs in visual association areas in the occipital, parietal and temporal lobes

16. Color vision Young-Helmholtz trichromatic theory
Red, green, blue color receptors in the retina
Stimulation of one or many results in color sensation
Opponent-process theory
Colors are analyzed in terms of opponent colors
Red vs. Green
Yellow vs. Blue
Black vs. White
One color turns some cells “on” and other cells “off”

17. Psychology of visual perception
Top-down processing means that what we see is influenced by biological, psychological and socio-cultural factors

18. Perceptual organization
How do we form meaningful perceptions from sensory information?

19. Gestalt psychology Branch of cognitive psychology
Organization of many sensations into perceptions of wholes
Based on experience and expectations
Perceived whole is not always the same as its parts!

20. Form perception Simplification into easily interpretable wholes
Figure-ground

21. Form perception Grouping principles Proximity Similarity Continuity
Connectedness
Closure

22. Depth perception Distance is perceived with vision and hearing
Visual depth perception
Binocular cues
Monocular cues

23. Binocular depth cues
Retinal disparity
Strongest visual depth cue

24. Monocular depth cues Light and shadow Relative size and position
Relative height/vertical position
Linear perspective

25. Auditory location cues
Intensity and pitch
Arrival times at each ear
Clarity

26. Perceptual constancy
Cognitive functions that maintain the features of an object, despite changing illumination, color, size, or shape
Based on comparisons between the figure and ground

27. Color and lightness constancy
Consistent color and light intensity, despite changes in illumination

28. Shape and size constancy
Familiar objects are perceived as unchanging despite changes in retinal images.

29. Perceptual interpretation
Making sense of the perceptions produced by the cortex
Genetics
Experience
Critical periods
Plasticity and adaptation

30. Perceptual set
Psychological predisposition to perceive stimuli in a particular way
Shaped by learned assumptions and beliefs
Affects how we interpret sensory stimuli
Examples

31. Other sensory modalities

32. Hearing
Stimulus - sound waves
Frequency
Amplitude

33. The ear

34. Auditory stimuli
Bending of hair cells in the cochlea transduces vibrations into neural signals
Auditory nerve
Primary auditory cortex
Auditory association cortex

35. Touch Stimulus - pressure, pain, warmth, cold
Receptors
Other sensations
Stimuli organized in primary somatosensory cortex
Perceptions created in somatosensory association cortex

36. Pain Critical alert system Subjective Physiology Prior experiences
Attention
Context
Culture

37. Pain
Gate-control theory
Pain control/management

38. Taste
Stimulus - chemical molecules that impart the sensations of sweet, sour, salty, bitter and umami
Tastebuds contain taste and touch receptors

39. Taste perception Flavor Begins in brainstem
Based on taste, olfactory, and touch stimuli
Begins in brainstem
Completed in the limbic system

40. Taste preferences Genetic predisposition Biological predisposition
Learned responses

41. Smell Stimulus - chemical molecules Receptors in olfactory epithelium
Axons project directly to the olfactory bulb of the brain
Perception begins in the olfactory bulb, completed in the limbic system

42. Kinesthesis & vestibular sense
Kinesthesis - sense of body position and movement
Vestibular sense - sense of head postion and movement
Stimulus - gravity and movement
Receptors found in muscles (body) and inner ear (head)

43. Kinesthesis & vestibular sense
Sensory signals about position and movement are organized in the medulla and cerebellum
Perception occurs throughout the brain
Brain stem
Temporal cortex