Sensation involves the detection of external or internal stimuli by sensory receptors, while perception is the interpretation and organization of sensory information. Sensation occurs via visual, auditory, olfactory, gustatory, somatosensory, and other sensory systems. Absolute threshold is the minimum stimulus level detectable by senses, while subliminal threshold is below conscious awareness. Perception involves internal and external factors and organizing sensations via Gestalt laws and past experiences. Disorders can impact sensation and perception, including reduced sensitivity, hallucinations, or inability to recognize stimuli.

1. Sensation and Perception

2. • A
Sensation
A sense is a system that translate information from outside the nervous system into neural
sense activity.
Sensation:
Sensation is an animal’s , including humans, detection of external or internal stimulation.
 Example: eyes detecting light waves, ears detecting sound waves
 It is different from perception, which is about making sense of or describing the
stimulation.

3. Sensation involves three steps:
 Sensory receptors detect stimuli
 Sensory stimuli are transduced into electrical impulses to be decoded
by the brain
 Electrical impulses move along neutral pathways to specific parts of
the brain where in the impulses are decoded into useful information
Sensory system:
The senses gathers information about the world by detecting various forms of
energy, such as sound, light, heat and physical pressure.
Example: the eyes detect light energy

4. How much stimulus is necessary in order to see, hear, taste, smell or feel something is threshold
Types of threshold
 Absolute threshold
 Subliminal threshold
 Terminal threshold
The minimum level of energy required by an external stimulus to be detectable by the human sense,
including vision, hearing, taste, smell and touch is called the absolute threshold.
 This term often used in neuro science and experimental research
 Can be applied to any stimulus that can be detected by human sense
Example:
 Vision - A candle flame 30 miles away
 Smell - A drop of perfume in a 6-room house.
Threshold:
Absolute Threshold:

5. Subliminal threshold:
When there is no sense of awareness of the stimulus and therefore they escape unnoticed, the
stimulus is in the Subliminal threshold.
Example:
 visual stimuli that is flashed so quickly on a screen that a person can't process it so therefore
they are unaware they have seen anything
 Eating popcorn while studying
Terminal threshold:
The maximum level of energy that can be detected by sensory organ is called terminal threshold.
 It is the maximum physical energy which can still be detected by a sense organ
 Beyond this threshold there will be no more sensation or sensation or sensation of other
modality

7. Types of Sensations:
 Visual Sensation
 Auditory Sensation
 Gustatory Sensation
 Olfactory Sensation
 Somatosensory
 Cutanous Sensation
 Proprioception
 Osmoreception

8. Visual:
The wavelength, intensity and complexity of light are detected by visual
receptors in the retina of the eye. There are two types of visual receptors:
1. Rods
2. Cones
Rods: Rods are sensitive to dim light, which makes them useful for seeing at night.
Cones: Cones are more sensitive to colour and bright light, which makes them more useful in
daylight.
Signals from rods and cones are transduced into useful neural information via optic nerve.
Blindness is the complete or nearly complete inability to see.
Auditory:
The frequency, intensity and complexity of sounds waves in the external world are detected by
auditory receptors (Cilia or hair receptors) in the ear. Different pattern of cilia movement lead to
different neural codes, which ultimately lead to hearing different loudness, pitch and timbre of
sounds. Deafness or hearing loss may occur in one or both ears.

9. Gustatory:
Taste receptors (i.e., taste buds or papillae) are activated by the presence of food or another object
on the tongue. Taste has four basic psychological qualities:
1. Sweet
2. Salt
3. Sour
4. Bitter
5. Most food derive their special taste from a unique combination of the four basic tastes.
Receptors Cells: The receptors cells for taste located on tongue are called taste buds. Papillae
contains taste buds. When parts of taste buds die or killed by very hot food, then new segments are
regenerated.
Olfactory:
Senses of smell serves many functions. The sense of smell originates in cells located high in the
nasal cavity, very close to the brain. Paths from these receptors to the brain is the most direct and
shortest of all senses.

10. Cutaneous Sensation:
Sensation on the skin are detected by the cutaneous receptors. These receptors may feel
sensation such as pain, tickle, cold, hot, soft and rough. Mechanoreceptors detect light pressure
(e.g., cares), vibration and texture, nociceptors detect strong pressure (e.g., pain) and
thermoreceptors detect temperature.
Example: If your dog lightly presses its nose on your leg, mechanoreceptors in your skin will sense
the smooth texture of your Dog’s nose whereas thermoreceptors will detect coldness. When dog
bite someone nociceptors detect the sharp pressure. Astereognosis is the inability to identify an
object by touch.
Somatosensory:
Somatosensory sensation occur when receptors detect changes on one’s skin or within one’s
body.

11. Proprioception:
Proprioception is the sense of the bodily position it includes the
vestibular sense ( i.e one’s sense of balance) and kinaesthetic sense (i.e
one’s awareness of one’s movements)
Osmoreception:
It is the body sensation of thirst when the amount of water in
one’s body falls below a certain threshold, the concentration of
osmolytes
Example: Salt, increase in one’s blood Osmoreceptor.

12. Loss of sensation:
 Loss of sensation means that you are unable to feel pain
, heat, cold…
 It is caused by complications of diabetes called
peripheral neuropathy. This is type of nerve damage
 Other condition that may cause you to lose feeling are
strocks spinal cord injury, tumors, and infections

13. Perception:
Process by which individuals organize and interpret their sensory impression in order give
meaning to their environment.
Components:
 Perceiver: The person who becomes aware about something and comes to a final
understand.
 Target: This is the person who is being perceived or judged.
 Situation: different situation may call for additional information about the target

14. .
Types of Perception:
 Vision
 Sound
 Touch
 Taste
 Smell
The steps in the perceptual process:
 The Environmental stimulus
 The Attended
 The Image on the Retina
 Transduction
 Neural Processing
 Perception
 Recognition
 Action

15. The Environmental Stimulus:
The environmental stimulus is Everything in our environment that has the potential to be perceived.
For example movements of the arms and legs or the change in position of the body in relation to
objects in the environment.
The Attended Stimulus:
The attended stimulus is the specific object in the environment on which our attention is focused.
Example, such as the face of a friend in crowd of strangers at the local coffee shop.
The Image on the Retina:
Next, the attended stimulus is formed as an image on the retina. The light actually passing
through the cornea and pupil and onto the lens of the eye. The cornea and lens act together
to project an inverted image onto the retina.
Transduction:
The image on the retina is then transformed into electrical signals in a process known as
transduction. The allows the visual messages to be transmitted to the brain to be interpreted.

16. Neural Processing:
The electrical signals then undergo neural processing. The path followed by a particular signal
depends on what type of signal it is (i.e. An auditory signal or a visual signal).
Perception:
Perception does not just involve becoming consciously aware of the stimuli .it is also necessary for
our brain to categorize and interpret what it is we are sensing.
Recognition:
Our ability to interpret and give meaning to the object is the next step known as recognition.
Action:
The final step of the perceptual process involves some sort of action in response to the
environmental stimulus.

17. Distortion in Perception:
 Personality
 Mental set
 Attributes
 First impression
 Hallo effects
 Stereo type
 Person perceived
 Situation factors

18. Factors influencing perception:

19. Internal Factors:
• Personality
• Motivation
• Experience
External Factors:
• Size
• Intensity
• Contrast
• Motion
• Repetition

20. • Personality: Personality traits influence how a person selects perceptions.
• Motivation: People will select perceptions according to what they need in the
moment. They will favour selections that they think will help them with their current
needs, and be more likely to ignore what is irrelevant to their needs.
• Experience: The patterns of occurrences or associations one has learned in the past
affect current perceptions. The person will select perceptions in a way that fits with what
they found in the past.
Internal Factors:

21. External Factors:
Size: A larger size makes it more likely an object will be selected.
Intensity: Greater intensity, in brightness, for example, also increases perceptual selection.
Contrast: When a perception stands clearly out against a background, there is a greater likelihood
of selection.
Motion: A moving perception is more likely to be selected.
Repetition: Repetition increases perceptual selection.

22. Gestalt laws of perceptual organization
• Law of Closure
• Law of Proximity
• Law of Similarity
• Law of Simplicity or Pragnanz
• Law of Continuity

23. Perceptual Learning:
Factors Affecting perception:
Based on past experiences or any special training that we get, every
one of us learns to emphasise some sensory inputs and to ignore
others. For example, a person who has got training in some
occupation like artistry or other skilled jobs can perform better than
other untrained people.
Mental Set:
Set refers to preparedness or readiness to receive some sensory input.
Such expectancy keeps the individual prepared with good attention
and concentration. For example, when we are expecting the arrival of
a train, we listen to its horn or sound even if there is a lot of noise
disturbance.

24. Motives and Needs:
Our motives and needs will definitely influence our perception. For
example, a hungry person is motivated to recognise only the food items
among other articles. His attention cannot be directed towards other
things until his motive is satisfied.
Cognitive styles:
People are said to differ in the ways they characteristically process the
information. Every individual will have his or her own way of
understanding the situation. It is said that the people who are flexible will
have good attention and they are less affected by interfering influences
and to be less dominated by internal needs and motives than or people at
the constricted end.

25. Sensory Disorder:
Sensory processing disorder is a condition in which the brain has
trouble receiving and responding to information that comes in
through the senses.
 ANESTHESIA: it loss of sensitivity that may either be due to a
psychological or psychogenic cause only specific parts of body have
anthesia in this case in the hands and in the legs respectively.
 Hyperesthesia: it increased or higher than normal sensitivity
 Hypoesthesia: decrease sentivity
 Paranesthesia:false perverted sensitivity

26. Perception Disorders:
Perception is sensation+meaning:any perceptual disrbance will
cause an abnormality in the interpretation of sensed sensory stimuli.
(a) Illusion-perceptual disturbance in the presence of stimuli
(b) a distortion of perception and an erroneous interpretation of
present stimulus
1. Normal illusion –this type of illusion is normal when everyone
can sense the stimulus.
2. Discriminative sensibility: An ability of locating stimuli that are
applied on the body; this ability is normal to everyone.
3. Abnormal illusion -ab illusion is abnormal when not everybody
can experience the illusion

27. Allochiria:
Wrong perception of stimuli or there is a displaced sensation.
Dyscuhiria:
Difficulty in localizing stimulus applied in the body.
a. Hallucination:
The perceptual distortion in the absence of stimulus.
a. Agnosia:
The patient appears to be confused that he cannot see
meaning or cannot identify and recognize the stimuli acting on the
senses.

28. Change in intensity:
Increased intensity of sensation – Hyperthesia seen in increasing
sensations or lowering of psychological threshold.
Symptoms of sensory processing disorder
Sensory processing disorder may affect one sense like hearing touch or
taste . It may effect multiple senses.

29.  In some children for example the sound of a leaf blower
outside the window may cause them to vomit or drive under
the table
 Many children with sensory processing disorder start out as
fussy babies who become anxious as they grow older.
 Many children has symptoms like these from time to time

30. Perception Activity:
How Do
YOU
Perciev
e?

31. This is all about Sensation and Perception
Represented by: Psychologists
Ahmad Raza 0154
Saima Nazir 0138
Iqra Ghaffar 0132
Maham Sarwar 0152
Eisha khalid 0149