Question

Weber discovered that for a difference between two stimuli to be perceptible, the stimuli must differ by at least a ______ proportion.

Short answer

The word missing from the exercise statement is 'constant'. Weber discovered that for a difference between two stimuli to be perceptible, the stimuli must differ by at least a constant proportion.

Step-by-step solution

Understand Weber's Law

Weber's law states that the smallest noticeable difference between two stimuli (also called the 'just noticeable difference' or JND) is a constant ratio of the original stimulus. This means that the fraction of change necessary to perceive a difference remains constant over different levels of stimulus.

Apply Weber's Law to the exercise

According to Weber's law, to tell if something has changed (like an increase in bright light, or in this case an abstract difference between stimuli), the stimuli must differ by a constant proportion. Therefore, the word missing from the blank in the statement is 'constant'.

Conclusion

In conclusion, the statement should read as: Weber discovered that for a difference between two stimuli to be perceptible, the stimuli must differ by at least a constant proportion. This underlines the principle set out by Weber's law.

Key concepts

Just Noticeable Difference

Imagine you're listening to music, and the volume is gradually turned up. There's a specific moment when you'll actually notice the sound is louder. This minimal change required to perceive a difference in the stimulus intensity is what psychologists call the 'just noticeable difference' (JND), a concept integral to comprehending sensory experiences.

According to Weber's Law, JND is not a fixed quantity but rather depends on a constant proportion relative to the original level of stimulation. For example, if you're holding a 100-gram weight, to feel that another weight is heavier, you might need it to be at least 102 grams—a 2% increase. However, if you're holding a 1-kilogram weight, a 20-gram increase might be necessary for the weight change to be noticeable. This 2% increase remains constant, reflecting the ratio aspect of JND.

For students, applying this concept to real-world situations can provide a tangible understanding. Like adjusting the temperature of a shower, a slight change might not be felt at all, but once it crosses the JND threshold, we immediately notice.

Stimulus Perception

Stimulus perception goes beyond simply recognizing that something has changed; it encompasses how we experience the different qualities of a stimulus, such as its intensity, duration, and complexity. The way our sensory systems translate the physical energy from stimuli into a perceived change is both fascinating and complex.

In everyday life, this translation affects everything from tasting food to feeling the warmth of the sun on our skin. The perceived intensity of these stimuli often follows a logarithmic scale, meaning that as the actual intensity increases, the perceived intensity does not scale up in a 1:1 fashion. Weber's Law helps explain this phenomenon, suggesting that our perception is relative and adaptive, rather than absolute.

To illustrate, when you walk from a dimly lit room into bright sunlight, initially you may find the light overwhelmingly bright, but your perception will quickly adapt. Although technically the stimulus (the sunlight's intensity) hasn't changed, your experience of the brightness certainly has.

Psychophysics

Psychophysics is a subfield of psychology that deals with the relationships between physical stimuli and the sensory perceptions they evoke. It quantifies the changes in sensory experiences given changes in stimulus properties, hence playing a crucial role in understanding how we interact with our environment.

The discipline uses precise mathematical modeling to describe how physical stimulus magnitude relates to the subjective magnitude of the perception. Weber's Law is a foundational principle in this field, showcasing a relationship between the incremental increase in stimulus intensity needed to produce a JND in a sensory experience. This law allows us to measure sensitivity to change across different sensory modalities, be it in vision, audition, taste, smell, or touch.

Psychophysics helps professionals in a range of fields, from product design, where ensuring changes in design are perceptible, to audiology, where determining the smallest change in sound intensity that a person can detect is critical. It represents the intersection of the physical world with our personal psychological experience of it.