Sensation & Perception Ch. 1-3: Review © Takashi Yamauchi (Dept. of Psychology, Texas A&M University)

Rat-man demonstration What does this tell? Why do we see two different things (a rat or a man)?

An interaction between –attention and perception –cognition and perception Tell me what you see.

Tired Old Sick Dark Slow Heavy Hospital ugly death

Beautiful Young Fresh Fast Energy Juicy Clean cheerful Vigorous

Ch 110 How come? –Different types of physical information (air vibration, light energy) are translated into a common language in the brain –  neural information Environmental Stimuli (e.g., light energy) Transduction Neural Processing Perception

What does this circle tell you? How are the circle and the rat-man demonstration related?

Levels of analysis –Psychological level –Physiological level –Single cell recording –EEG/ERP –PET Scan / fMRI –What are they?

Single cell recording

PET & fMRI

fMRI Setup

Detection –Absolute threshold –Difference threshold Can you define them?

DL (difference threshold) Weber’s law

The impact of standard stimuli DL (difference threshold) gets larger as the standard stimulus gets larger. Weber’s law DL/S=K DL: difference threshold S: standard stimulus K: constant

Weber’s law

Question: With a standard stimulus 1 kg, John’s difference threshold was 0.25kg. With a standard stimulus 10kg, what would be John’s difference threshold?

Question: With a standard stimulus 1 kg, John’s difference threshold was 0.25kg. With a standard stimulus 10kg, what would be John’s difference threshold? DL/S=K DL: ? S: 10 K: DL/S=K DL: 0.25 S: 1 K: 0.25

Magnitude estimation What is it?

Magnitude estimation

Standard: == 10 Target: == ? Standard: == 100 Target: == ?

Steven’s power law P = K S^n P: perceived magnitude K: constant S: stimulus intensity n: a power

Neurons Dendrites Cell body Axon

Neuron Neurotransmitter Synapse Action potential Dendrites Axon Cell body Excitatory and inhibitory connections

Rods and cones Morphology Their roles Distribution on the retina Their connections

Photo receptors: Rods and cones

The distribution of cones and rods on the retina Cones are concentrated mainly on the fovea. There are no rods on the fovea. We move eyes to capture images on the fovea.

Convergence: –The ratio of connections with two groups of neurons. –Rods vs. Ganglion cells 120:1 –Cones vs. Ganglion cells 6:1

Why does this matter?

Time 0t The frequency of action potential Time 0 t The number of action potential emitted by a neuron is correlated with the intensity of the stimulus. Time 0 t

How do you detect there are two separate dots (lights)?

Questions: What happens to B?

ExcitatoryInhibitory

Questions: What happens to B?

Receptive field The receptive field of a neuron in the visual system is the area on the retina that influences the firing rate (action potential) of the neuron. Measuring the receptive field of a ganglion cell

Measuring a receptive field of a ganglion cell Change the size of the stimulus and see the way a ganglion cell respond

Cones Ganglion cell B

=sum(B)

Physical stimuliYour perception

Lateral inhibition

(a)= -h’ + h -h’ (b)= -h’ + h -l’ (c)= -h’ + l -l’ (d)= -l’ + l -l’ h > l h’ > l’, -h’<-l’ H L HHHLLL hhhlll h’ l’ h’l’ (A) (B) (C) (D) (a) (b) (c) (d) (a)<(b), (c) <(d)

Lateral inhibition (a)= -h’ + h -h’ (b)= -h’ + h -l’ (c)= -h’ + l -l’ (d)= -l’ + l -l’ h > l h’ > l’, -h’<-l’ H L HHHLLL hhhlll h’ l’ h’l’ (A) (B) (C) (D) (a) (b) (c) (d) (a)<(b), (c) <(d)