We all have sensed so many things in our daily life like cold, hot, bright, painful, exciting, etc. What do we use our senses for; for example nose for smell, ears for hearing, tongue for taste and skin for touch. So, what is sensation? a simple answer to that is what we sense through our body parts-that is sensation. A quick question for you, ‘How many senses do we have?’ 5!, ‘Are you sure ? Search it on google, you will be amazed.
So, let’s see sensation in psychological sense. Sensation is a simple, primary, cognitive process in which the individual merely becomes aware of immediate present stimuli in the environment.
What is Psychophysics?
Psychophysics is the study of quantitative relationship between physical energy resultant and sensory experience. Researchers claim that psychophysics is an exact science of functional relations of dependency between mind and body.
Gustav Fechner, founder of psychophysics was the pioneer in experimental psychology, a physician and a mathematician. He gave these methods for constructing scale for the measurement of relationship between characteristics of physical stimuli and attributes of our sensory experience.
Basic Concepts of Psychophysics
Threshold: The concept was proposed by Herbert. It is defined as boundary value which separates stimulus that produces the response from a stimulus that produces a difference.
- The concept has been originated from Limen.
- It is related to Consciousness.
- Threshold is strongly related to Sensitivity.
- Threshold and sensitivity are inversely proportionate.
What are the simple Types of Threshold?
1. Absolute Threshold:
- Absolute threshold is a boundary point in sensation.
- Absolute Threshold is the lowest level of stimulation that a person can consciously detect 50% of the time the stimulation is present.
- It separates presence of sensory experience from absence of experience when physical stimulus reaches a particular point.
- It refers to minimum value of a physical stimulus which gives rise to sensation.
- It is also called RL (Reiz Limen ) or AL (Absolute Limen), which originated from German language.
- Sensitivity induced by AL is known as Absolute Sensitivity.
- Absolute Sensitivity is defined as the limit of an organism’s capacity to respond to stimulation.
- For example of Absolute Threshold – Sight – A candle flame at a distance of 30 miles on a clear, dark night. Hearing – The tick of a watch 20 feet away in a quiet room. Taste -1 teaspoon of sugar in 2 gallons of water
2. Differential Threshold
- It is the organism’s capacity to respond to differences both qualitatively and quantitatively.
- It is also called as DL (Differential Limen).
- It refers to the mean of all DL values taken over several trials by the same subject for the same stimuli.
- For example – Change in the weight of a constant stimuli and a comparative stimuli (weight stone 1kg).
3. Terminal Threshold
- Terminal threshold is that upper range value of the stimulus at which the organism stops receiving sensation.
- The sensitivity related to terminal threshold is known as terminal sensitivity.
- Terminal Sensitivity refers to the upper most limit of the organism’s capacity to respond to a stimulus.
- For example – Most of the human beings can not sense sound waves above 20,000 Hz s due to his/her limited capacity.
What are the Psychophysical Methods?
1. Method of Limits:
- It is a method to observe the AL and DL values in an experiment.
- Due to presentation of the stimuli, even small changes in them are observed by the researcher.
- Stimuli are always presented in ascending / descending order.
- Errors related to Method of limits
- Constant Error – it is defined as a systematic tendency on the path of the subject to overestimate or underestimate the given value of the stimuli.
- Error of Habituation – it is committed when subject falls into the habit of giving certain response even after a clear change in the stimulus has occurred.
- Error of Anticipation/ Expectation – it is defined as the tendency to expect the change earlier than the point at which actual reversal in sensation takes place.
- Variable Error – it is defined as the error or judgement which results due to the variation in motivation or attention of the subject or due to uncooperativeness of the subject.
2. Method of Constant Stimuli:
- This method is used to calculate AL (Absolute Limen) and AL (Absolute Limen).
- Here, stimuli are presented in random order instead of ascending and descending order.
- Each stimulus is presented equal number of times over the entire series.
- Concept of Upper threshold (UT) and Lower threshold (LT) are introduced in this method.
- DL (Differential Limen). is calculated with the help of UT and LT.
3. Method of Average Error or Method of Adjustment.
- It is called as method of average error because Subject adjusts comparative stimulus as per the standard stimulus to make both of them equal in this method.
- Generally this method is not useful to find AL (Absolute Limen).
- This method is also used to find illusionary effect.
- Every point is PSE (Point of Subjective Equality) in this method as every point is a comparative judgement.
- DL (Differential Limen) is not directly found but estimated by the method.
- Two errors related this method–
- Space Error : An error occurs due to the spatial position / direction of Standard stimulus (St).
- Movement Error : The error occurs due to inward and outward movement which subject is required to do in order to adjust Stimulus of variability (Sv) as equal to Standard stimulus (St).
Click here to check your understanding of this topic by solving this short test – MCQ test – Sensation