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Figure-Ground Perception

Consolidated by 

Akshata Jayant Chonkar (1630221)

I CEP-B

Christ University, Bangalore

Figure-ground perception has evolved from the Gestalt school of thought. Figure–ground organization is a type of perceptual grouping which is a vital necessity for recognizing objects through vision.

Perceptual organization is a construct of the Gestalt School of thought. Gestalt theory was first developed in the early 1900s by Austrian and German psychologists. Some of the notable founders of Gestalt theory include Max Wertheimer, and Kurt Koffka. One of the main beliefs of Gestalt theory is that a something as a whole consists of interacting parts that can be separated, analyzed, and rearranged in the whole. In other words, the whole is different from the sum of its parts. Max Wertheimer and scientists with him believed that humans have an inborn tendency to construct meaningful perceptions from fragments of sensory input. This theory of perception proposes that people make sense of the world around them by taking separate and distinct elements and combining them into a unified whole. For example, if you look at shapes drawn on a piece of paper, your mind will likely group the shapes in terms of things such as similarity or proximity. 

People automatically focus on some objects in the perceptual field to the exclusion of others. What we focus on is the figure, and what fades away is the the background.

When a person sees buildings, cars, trees, people, etc.- all these objects are perceived as figures in front of backgrounds of the sky, or other buildings, etc. When figure-ground relationships are ambiguous, or capable of being interpreted in various ways, our perceptions tend to be unstable, shifting back and forth. An example of this would be a reversible figure, which is a drawing that one can perceive in different ways by reversing the figure and ground. In some examples, a shift occurs in our perceptions of what is figure and what is ground.

Psychologists have created different kinds of stimuli in order to study how people separate figure from ground. The interpretations that people derive from these stimuli are real, even though the objects are ambiguous or are nonexistent.  

 The "faces or vases" illustration is one of the most frequent demonstrations of figure-ground. What you see depends on whether you see the white as the figure or the black as the figure.

If you see the white as the figure, then you perceive a vase. If you see the black as the figure, then you see two faces in profile. Most people are able to reverse their perceptions and switch back and forth between the vase and faces images.

When looking at a visual scene, people tend to look for ways to differentiate between the figure and the ground. Some ways that people accomplish this include:

Blurriness: Objects in the foreground tend to be crisp and distinct while those in the background are blurry or hazy.

Contrast: High contrast between objects can lead to the perception of figure and ground The Rubin vase is one example.

Size: Images that appear to be larger will be perceived as closer and part of the figure while those that are smaller will seem further away and part of the background.

Separation: An object isolated from everything else in a visual scene is more likely to be seen as a figure versus background.

Law of common fate: Elements seen moving together are perceived as belonging together

All of these laws help us understand how people transform raw visual inputs into meaningful displays

Bibliography

https://en.wikipedia.org/wiki/Figure–ground_(perception

http://study.com/academy/lesson/figure-ground-perception-definition-examples.html

https://www.verywell.com/what-is-figure-ground-perception-2795195

Introduction to Psychology, Clifford T. Morgan, Richard King; 7th Edition; McGraw Hill Educatin Pvt Ltd

Psychology- Robert A Baron; 5th edition; Pearson Publications

Psychology: Concepts and Connections- Spencer A. Rathus ; 7th Edition; Thomson and Wadsworth

Psychology- Saul Kassin; 2nd Edition; Hall

BASIC CONCEPTS OF SENSATION

Consolidated by

Abhishek Singh Chauhan, 1630201, I CEP B

Christ University, Bangalore, Karnataka 

As defined by APA Glossary of Psychological Terms, sensation is the process by which stimulation of a sensory receptor gives rise to neural impulses that result in an experience, or awareness of, conditions inside or outside the body.

In simpler words sensation can be explained as the process by which our sense organs receive inputs from our environment. Hence, the classical human senses – sight, sound, taste, smell and touch– register the sensory inputs that evoke our respective sense organs. But it is important to note that the scope of sensory experience is much wider than the basic functions of these five senses, as sensory information can also be in the form of light, pressure, vibration, heat and pain. These are the stimuli to which our nervous system reacts through sensory receptors.

 A stimulus is a physical influence that initiates and provokes a reaction. It can be specific information that is received by the sensory organs, and the resulted experience is a sensation. Stimuli can vary in type and intensity. Different sense organs respond to different stimuli, and the intensity of the stimulus decides whether it can be deducted by the sensory receptors. This is the core subject matter of the branch of psychology called psychophysics, which studies the physical characteristics of stimuli in relation with our psychological reaction to them.

Sensory receptors are the specialized structures that react to a physical stimulus. A group of receptor cells is called a sense organ. These receptors vary in classification –taste, gustatory, odour, olfactory, etc. – but perform the same basic function of being in contact with the physical stimulus to receive information, decode this information into creating neural impulses or signals, and transmit these impulses to sensory cortices of the brain for it to interpret them. This interpretation is called perception.

 Sensation and perception are often explained as one unit. These are two interrelated but distinct parts of a continuous process. Sensation is a physical response of detecting and translating the sensory information into signals going up to the brain (bottom-up processing), while perception  is a psychological response that follows it by analysing and interpreting these signals and makes sense of them based on our experiences and expectation (top-down processing).

A stimulus has to be strong enough to be detected by the sense organs. For that, it has to have the smallest level of intensity to be registered by our senses, which is called an absolute threshold. However, at such low levels, it may be difficult to detect a stimulus if noise (any disturbance or distraction in the form of background stimulation that interferes with other senses) is present in the environment. Therefore, an absolute threshold is defined as a level of stimulus that is detectable 50 percent of the time. These thresholds may vary with age.

The minimum change in stimulus intensity required to detect the difference in sensory experience 50 percent of the time is called difference threshold or a just noticeable difference. Ernest Weber observed that the size of difference threshold is a constant proportion of the original stimulus magnitude. This relation is called Weber’s Law and is expressed as ∆I / I = K, where ∆I represents the difference threshold, I represents the initial stimulus intensity and K signifies the proportion that remains constant despite changes in I. For examples, if two cell-phones are playing music with the intensity of 100 units, and one’s volume is increased just enough for it to be noticeably louder, the increased volume would have the intensity of 110 units, and the just noticeable difference would be 10. The Weber fraction in this would be 10/100 = 0.1. This being a constant proportion, a person’s difference threshold can be predicted for any level of intensity using the law.

Due to repeated exposure to a stimulus, our sensitivity to it decreases. This happens through sensory adaptation, which is an adjustment our brain makes to accustom itself to an unchanging stimulus. This happens when a strong odour in a room can no longer be smelled after a while. It is not because the smell vanishes, but our nerve cells fire less frequently in response to the continuous exposure, and we adapt to it.

BIBLIOGRAPHY:

·  Feldman, Robert S. (1986) Essentials of Understanding Psychology. New York City, NY, USA: McGraw-Hill  Education. (pp. 91-96)

· Myers, David G. (2009) Psychology – 9th edition in modules. New York City, NY, USA: Worth Publishers. (pp. 225-231) 

  Glossary of Psychological Terms – American Psychological Association.                           

       URL: www.apa.org/research/action/glossary.aspx