Sensation & Perception First Week

Psychophysical correlates of light: light wavelength correlates to

Hue/color

Psychophysical correlates of light: different amplitudes correlates to

Brightness

Psychophysical correlates to light: purity of wavelength

Saturation

Perceptual sensitivity is

Weakest pressure that can be felt

Perceptual acuity is

How accurate or sensitive we are to change

Sensory threshold

Measure the limits of sensory systems, they are a measure of minimums. The smallest stimulus that can be detected.

Proximal stimulus

What is in our brain, proximity (in here). The stimulus on the receptors. In vision, this would be the image on the retina.

Distal Stimulus

What is in the distance, “out there”. Stimulus in the external environment.

Representation

This is the third part of the perceptual process, it is mental and the processed “image”

Transduction

Transducers are the receptors and translators of energy in the world to neural impulses.

Doctrine of Specific Nerve Energies (SNE)

Suggests that our preceptor experience has more to do with the nerves and brain areas that are stimulated and less to do with the world itself.

Examples of how to measure physiology (biological response)

Brain scans (fMRI/EEG): records the electrical activity or blood flow in the visual cortex or temporal lobe when presented a stimulus.

Single-Neuron Recording: measuring the firing rate of individual sensory receptor cells when physical energy is applied

Brain Lesion: examining how damage to a specific neural pathway changes biological signals

Examples of how to measure perception (behavioral/mental response)

Absolute threshold testing: presenting dim light or quiet sounds to find the minimum intensity a person detects 50% of the time (measures senitivity)

Two-point discrimination (acuity): poking the skin with two thin hairs and asking if someone feels 1 or 2

Webers law/difference threshold: asking a participant to compare two weights or brightness levels to determine how much physical change is required before they report a noticeable difference.

Measuring physiology

Measuring biological activity directly

Measuring perception (behavioral)

You are measuring conscious experience or behavior (asking someone “did you hear that?”, using Weber’s law to find a difference threshold or testing two point skin acuity).

Stimulus-Physiolgy(Perceptual Relationship)

Energy in the world turns into biological response (shining light into an eye and measuring optic nerve impulses)

Stimulus-Perception(Perceptual Relationship)

Energy in the world turns into behavioral response (raising light intensity until the person notices, aka psychophysics)

Stimulus-Perception(Perceptual Relationship)

Energy in the world turns into behavioral response (raising light intensity until the person notices, aka psychophysics)

Two main types of sensory receptors

Mechanoreceptors (respond to mechanical energy like pressure/vibration for touch and hearing)

Photoreceptors or chemical receptors (respond to electromagnetic energy for vision or chemical energy for smell/taste)

Webers law calculation. (10 candles, Weber fraction 0.10)

JND=k x level of stimulation

JND=0.10×10=one candle

You need to add one candle (total of 11) to perceive a change in brightness.

Methods to measure perception

• Method of Limits: Adjusting stimulus intensity in step-by-step ascending or descending order until perceived.

• Magnitude Estimation: Assigning numbers to rate how intense a stimulus feels.

• Reaction Time: Measuring how fast a participant responds after a stimulus appears.

• Recognition: Testing whether a participant can categorize or identify what a stimulus is.