Chapter 1 Psychology

I. Our Senses Encode the Information Our Brains Perceive * Synesthesia- The perceptual experience of one sense that is evoked by another sense * For many years scientists dismissed synesthesia as rare curiosity or outright faking * Far more common than previously believed * Brain regions for different sensory modalities cross-activate one another * Sensation- Simple stimulation of a sense organ * Perception- The organization, identification, and interpretation of a sensation in order to form a mental representation * Transduction- What takes place when many sensors in the body convert physical signals from the environment into encoded neural signals sent to the central nervous system i. Psychophysics
Psychophysics- Methods that measure the strength of a stimulus and the observer’s sensitivity to that stimulus
Gustav Fechner * ii. Measuring Thresholds * Absolute threshold- The minimal intensity needed to just barely detect a stimulus
A threshold is a boundary
Boundary between two psychological states
Human perceptual system excels at detecting changes in stimulation rather than the simple onset or offset of stimulation
Just noticeable difference (JND)- The minimal change in a stimulus that can just barely be detected
If a light is bright, it will take a much larger increment to detect the difference and make the JND larger
JND can be calculated for each sense
It is roughly proportional to the magnitude of the standard stimulus
Weber’s law- The just noticeable difference of a stimulus is a constant proportion despite variations in intensity
Ernst Weber- noticed the relationship between the JND and the magnitude of the standard stimulus
When calculating a difference threshold, it is the proportion between stimuli that is important; the measured size of the difference, whether in brightness, loudness, or weight, is irrelevant iii. Signal Detection
A lot of other stimuli get in the way of sensing just one