Chapter 4: Sensing the Environment

[blank_start]Sensation[blank_end] refers to the process by which sense organs gather information about the environment and transmit it into the brain for initial processing.

[blank_start]Perception[blank_end] refers to the closely related process by which the brain selects, organizes, and interprets sensations.

Psychophysics studies the relationship between

Specialized cells that all sensory systems contain are called [blank_start]sensory receptors[blank_end].

Sensory cells

Within each sensory modality, the brain codes sensory stimulation for

The common features of the senses are that they

The absolute threshold refers to the maximum amount of physical energy (stimulation) needed for an observer to notice a stimulus.

[blank_start]Vision[blank_end] A candle flame 30 miles away on a dark, clear night. [blank_start]Hearing[blank_end] A watch ticking 20 feed away in a quite place [blank_start]Smell[blank_end] A drop of perfume in a six-room house [blank_start]Taste[blank_end] A teaspoon of sugar in 2 gallons of water [blank_start]Touch[blank_end] A wing of a fly falling on the chichi from a height of a centimeter

[blank_start]Difference threshold[blank_end] refers to the lowest level of stimulation required to sense that a change in stimulus has occurred.

[blank_start]Just noticeable difference[blank_end] is the smallest difference in intensity between two stimuli that a person can detect.

JND explained in relation to a stimulus can be shown as

This law states that regardless of the magnitude of two stimuli, the second must differ by a constant proportion from the first for it to be perceived as different.

This law holds that the physical magnitude of a stimulus grows logarithmically as the subjective experience of intensity grows arithmetically... So people subjectively experience only a small percentage of actual increases in stimulus intensity.

This law states that subjective intensity grows as a proportion of the actual intensity raised to some power... So sensation increases in a linear fashion as actual intensity grows exponentially.

[blank_start]Sensory adaptation[blank_end] is the tendency of sensory systems to respond less to stimuli that continue without change.

An example of Weber's law is that if you are holding a 50 lb bag it only takes one pound to be perceived as different. If you are holding a 100 lb bag it only takes 2lb. So 1:50 ratio.

An example of Steven's power law is that if there is more pain, there is less addition intensity required for a JND.

An example of Fechner's law is your ears adapting at a concert or the eyes to the lighting from the sunlight to the lighting in a movie theatre.

The three basic principles that apply across all of the senses are:

The process of converting physical energy or stimulus information into neural impulses is called [blank_start]transduction[blank_end].