Chapter 5 – Sensory, Perception and Attention
Sensation – how sense organs respond to external stimuli and transmit the responses to the brain
Perception - the processing, organization and interpretation of sensory signals that result in an internal
representation of the stimulus and a conscious experience of the world.
How Do We Sense Our Worlds?
Stimuli must Be Coded to Be Understood by the Brain
The way our sensory organs translate a stimulus’s physical properties into neural impulses is called
Transduction – a process by which sensory receptors produce neural impulses when they receive
physical or chemical stimulation.
Most sensory information goes to the thalamus which sends information to the cortex where the
incoming neural impulses are interpreted as sight, smell, sound, touch or taste.
Sensory coding is either quantitative or qualitative. Quantitative factors such intensity, brightness and
loudness are indexed by neural firing frequency. Qualitative coding, useful for things like colour and
taste, are facilitated by certain types of receptors being able to code for certain types of stimuli.
Psychophysics Relates Stimulus to Response
The focus of psychophysics is to examines our psychological experiences of physical stimuli. It tests our
ability to observe change and how we respond to the change. As a result, we can test the limits of the
human sensory system.
Absolute threshold – the minimum intensity of stimulation that must occur before one can experience a
Difference threshold – the minimum amount of change required in order to detect a difference between
intensities of stimuli
Weber’s law – the size of a just noticeable difference is based on a relative proportion of difference
rather than a fixed amount of difference. (e.g. you can tell difference between 1 ounce and 2 ounce but
not 5 lbs and 5.1 lbs)
Sensory adaptation – when an observer’s sensitivity to stimuli decreases over time.
What are the Basic Sensory Processes?
Neurons “speak” to other neurons and from this our conscious experience arises. The first step in this
process begins with the detection of stimuli.
In gestation, taste buds are chemical detectors
Taste buds – sensory receptors that transducer taste information
Microvilli – short, hairlike structures at the tip of each taste bud. When stimulated, they send electrical
signals to a brainstem region called the medulla and from there to the thalamus and cortex, thus we
In Smell, the Nasal cavity Gathers Particles of Odour
Odourous particles pass into the nose. The come into contact with olfactory epithelium which trigger
chemical receptors where nerve impulses convey information to the olfactory bulb.
Olfactory bulb – the brain centre for smell, located below the frontal lobes.
Prefrontal cortex = smell is aversive or pleasant amygdala = intensity of smell In touch, sensors in the skin detect pressure, temperature and pain
Haptic sense – sense of touch
Anything that makes contact with our skin provides tactile stimulation gives rise to touch sensation.
Two kinds of nerve fibres identified for pain: fast fibres for sharp, immediate pain (protect