Sensory Thresholds, Perception and Optical Illusions

Sensory Thresholds and Psychophysics

Sensory thresholds. Psychophysics studies the relationship between the physical nature of a stimulus and the sensory responses that occur in a person. Our ability to detect stimuli relies on different sensory thresholds:

• Absolute threshold: the minimum amount of stimulus we need to be aware of something and also the maximum amount of stimulation we can tolerate.
• Differential threshold: the difference in stimulus intensity needed to notice an increase or decrease prior to the stimulus.

Cognitive theory. Cognitive psychology researches how people process information and how these processes are represented in the world, and how these representations determine behavior. The terms feeling and perception are related but distinct: a feeling is detecting something without knowing what it is, while perception is recognizing a specific object or event.

The sensory experience collects information, and perception is related to the interpretation of that information. Complex issues affect human perception and expectations, including values, goals, or cognitive schemata. A cognitive schema is an organized set of data or knowledge stored in memory, used to interpret reality and that integrates our experiences and knowledge.

Optical Illusions and Perceptual Mechanisms

Optical illusions. When we analyze these illusions we see how easily our senses can deceive us. Illusions are discrepancies between what we perceive and objective reality. The analysis of optical illusions or perceptual distortions helps identify brain mechanisms and build hypotheses about internal or external reality. A feature of perceptual illusions is the brain's persistence in dealing with these anomalies.

Perceptual disorders:

• Agnosia: the inability to identify or recognize particular sensory stimuli, even when intellectual capacity is intact.
• Illusions: an illusion is a distortion of the perceived object, caused by a misrepresentation or error in the sensory survey. There are several types:

1. Factual illusions: common in everyday life; perceptions that differ from external reality in ordinary contexts.
2. Catathymic illusions: objects or situations that become distorted under the influence of feelings and emotions.
3. Pareidolia: illusions of fancy, typical of the imagination, such as seeing more or less definite figures on a wall or in the clouds. This phenomenon gives a formal structure to something that does not actually have it.