PYB102 Introduction to Psychology 1b Exam Revision Week 2 .doc

9 Pages
Unlock Document

Daniel S.Joyce

PYB102 Introduction to Psychology 1b Week 2 Lecture Perception • perceptual psych. study the way we acquire info about the world via our various senses • bulk of perceptual research has been conducted in vision and audition domains Vision Light • for an object to be visible, it must emit or reflect light • The human eye is only capable of detecting light within a narrow range of wavelengths • Within this range of visible wavelengths, different wavelengths give rise to the perception of different colours Gross anatomy of the eye • The pupil changes in diameter (dilates) to accommodate changes in lighting Light is detected by receptors called rods and cones located at back of • retina • Schultze proposed that rods and cones form two separate visual systems (Duplex Retina Theory); • Photopic: Bright light vision via cones • Scotopic: Dim light vision via rods • Von Kries (1895) observed that individuals without rods were night blind. • The reverse applies for individuals without cones Normal colour vision in humans is trichomatic: Cones can contain either L (long), M (medium) or S (small). ← •All the colours which you can see are due to this combination of signalling by rods and cones •Some animals have more advanced colour vision than humans ← Colour deficiencies • Retinal "colour blindness" occurs in 8% of the male population (x-linked), <1% of females • Two main varieties: • anomaly of the photopigment (Altered spectral sensitivity) • deletion of the photopigment (dichromacy) • Protanopia – no L cones (red-green colour blind) Deuteranopia – no M cones (red-green colour blind) • • Tritanopia – no S cones (blue-yellow colour blind) Information Reduction Ganglion cell receptive fields • Each ganglion cell receives input from a number of adjacent receptor cells • These cells form the receptive field of the ganglion cell • Micro-electrode recordings indicate that many ganglion cells respond differently depending on whether the centre or the surround of their receptive field is illuminated • In some centre-surround receptive fields, illumination of the centre is excitatory while illumination of the surround is inhibitory. • This is called centre-surround antagonism The Visual Cortex • Optic nerve projects to the LGN, and then to the visual cortex in the occipital lobe at the rear of the brain • The VC is approximately 2 mm thick and contains ~100 million cells in 6 main layers with more complex behaviours • The LGN fibres enter layer IV, where the neurons have centre-surround receptive fields like those of ganglion cells • In other layers we find neurons with more complex behaviours Feature detectors in the visual cortex • Simple cortical cells respond to bars of a particular orientation • Complex cortical cells often respond best to a correctly oriented bar moving across the entire receptive field. Some cells are even direction sensitive • Hypercomplex cortical cells fire only to moving lines of a particular length or moving corners or angles • Summary: These cortical cells act as feature detectors Optical Illusions • The brain assumes that objects that are far away are bigger than they appear, therefore the top line appears longer than the bottom line. Blindsight • Rare condition in which a person lacks conscious perception of part or all of their visual field • Ability to detect, but not be aware of stimuli o Capacity to respond to visual information o Often expressed as a ‘feeling’ rather than a visual percept • Blindness is cortical (often in the VC) rather than from lower order processes (i.e., retina functions normally) • Behaviours are often automatic and informed by stimuli of which we can be completely unaware • Some people can experience blindsight just on one side of their vision The Stroop effect Interference of a reaction time task Conditions: no conflict vs conflict o Neutral, congruent, and incongruent o Reaction time (RT): incongruent> neutral> congruent Reading is an automatic task o Semantic meaning of the words takes priority o Semantic interference occurs when asked to name the incongruent colour of the text o Colour naming is not automated -> additional cognitive load required which increases RT o Semantic facilitation when asked to name the congruent colour of the text, RT decreases Taste • Sapid (tastable) substances must generally by water soluble • Most researches agree that there are four basic tastes: Sweet, Sour, Bitter, Salty • • Other researchers suggest metallic and unami (savoury) • These primary tastes are associated with substances w/ particular chemical properties Swe Generally associated with organic molecules like sugars & et alcohols. Many sweet substances (including non- organic ones) contain a component consisting of two negatively charged atoms and a positively charged hydrogen atom (AB,H system) Sour Generally associated with acids Bitte Often taste sweet in small amounts and often contain an AB,H r system many bitter substances contain nitrogen Salt Salty substances break into two electrically charged parts (ions) y when dissolved they size of the negative ion determines the saltiness (lighter = more salty) Overview of taste physiology Transduction of this chemical information into electrical signals occurs in taste buds: • Located in pits around papillae on the tongue, and on the soft palate • ~10000 taste buds, decreases with age • Taste buds contain a number (~50-150) of taste cells • Taste cells terminate in microvilli which project into the taste pore • Microvilli seem to be the site of reception for chemicals • Taste cells are replaced every few days • Nerve fibres exit from the back of the taste cells Models of taste coding Most taste receptors seem to respond to all 4 basic tastes, although with different sensitivities (Kimura & Beidler, 1961) • The cross-fiber patterning model (e.g., Pfaffman, 1955) argues that each substance we can taste generates a different pattern of activity across nerve fibres leading to different taste perceptions • Erickson (1963) noted that the pattern for potassium chloride and ammonium chloride are similar but that for sodium chloride is different; • Groups of rats fed one of these accompanied by an electric shock o KCl rats subsequently avoided NH4CL and visa versa, but the NaCl rats did not avoid either of the other 2 salts o Thus pattern of neural activity seems to correlate with taste The labelled-line theory (Pfaffman, 1974); • Assumes a best stimulus model of nerve fibre activity where specific fibres encode one of the four basic tastes depending on the one they respond
More Less

Related notes for PYB102

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.