Download Sensory, Attentional and Perceptual Processes: Understanding How We Know the World and more Study notes Cognitive Psychology in PDF only on Docsity!
CHAPTER 4:
Sensory, Attentional and Perceptual Processes
Knowing the world
● Knowledge about the objects around us comes from our sense organs (e.g., eyes , ears ), which collect information from both the external environment and our own bodies. ● Our knowledge of the world around us depends on three basic processes, called - ● Sensation ● Attention ● Perception. ● These processes are highly interrelated; hence, they are often considered as different elements of the same process, called cognition. ● Sensation involves detecting and registering information about various objects through our senses. ● For information to be registered, objects must capture our attention , focusing on their attributes like size, shape, and color. ● The brain processes and constructs meaning from the sensory information received, integrating sensation and attention into our understanding of the world.
Nature and Varieties of Stimulus
The external environment around us is filled with a diverse array of stimuli.
● A stimulus is any object or event that elicits a response.
These stimuli can be perceived through various senses:
- Visual Stimuli: ○ Examples include objects like a house. ○ Visual stimuli are detected by our eyes, which are responsible for vision.
- Auditory Stimuli: ○ Examples include sounds such as music. ○ These stimuli are detected by our ears, which are responsible for hearing.
- Olfactory Stimuli: ○ Examples include scents such as the fragrance of a flower. ○ These stimuli are detected by our nose, which is responsible for the sense of smell.
- Gustatory Stimuli: ○ Examples include tastes like sweets. ○ These stimuli are detected by our tongue, which is responsible for the sense of taste.
- Tactile Stimuli: ○ Examples include sensations such as the softness of a cloth. ○ These stimuli are detected by our skin, which is responsible for the sensations of touch, warmth, cold, and pain.
Humans are equipped with seven specialized sense organs, known as sensory receptors or information-gathering systems, because they receive and gather information from various sources:
○ Eyes: For vision. ○ Ears: For hearing. ○ Nose: For smell. ○ Tongue: For taste. ○ Skin: For touch, warmth, cold, and pain.
Besides these five external sense organs, we have also got two deep senses-
○ Kinesthetic System: kinesthetic senses are the senses of position and movement of the body. ○ Vestibular System: contributes to our ability to maintain balance and body posture.
Sense Modalities
Our sense organs provide us with direct information about both the external and internal worlds.
The initial experience of a stimulus or object registered by a sense organ is called SENSATION.
Sensation involves detecting and encoding various physical stimuli, resulting in immediate basic experiences like "hard," "warm," "loud," and "blue."
Each sense organ is highly specialized to handle specific types of stimuli, making each one a distinct sense modality.
Functional Limitations of Sense Organs
○ Limitations in Sensing Stimuli: ○ Our eyes cannot see extremely dim or overly bright objects. ○ Our ears cannot hear sounds that are too faint or too loud. ○ Other sense organs have similar limitations in their functioning.
○ Range of Stimulation: ○ Human sensory organs operate within a limited range of stimulation. ○ For a stimulus to be noticed, it must be of an optimal intensity or magnitude.
- Search , where an observer looks for some specified subset of objects among a set of objects.
● Attention has a -
- Central focus - When the field of awareness is centered on a particular object or event it is known as the focus or focal point of attention.
- Fringe - when the objects or events are away from the center of awareness and one is only vaguely aware of them, they are said to be at the fringe of attention.
Types of Attention
Types of attention-
- Selective attention: Involves choosing a limited number of stimuli from a large set of available stimuli.
- Sustained attention: Pertains to the capacity to sustain focus on a particular stimulus over an extended period.
Note: Sometimes we can also attend two different things at the same time, which is called divided attention.
1. Selective Attention
● Selective attention is concerned mainly with the selection of a limited number of stimuli or objects from a large number of stimuli. ● Our perceptual system has a limited capacity to receive and process information. Which means that it can deal only with a few stimuli at a given moment of time.
Factors Affecting Selective Attention:
➔ External Factors: These factors are associated with the characteristics of stimuli.
● Factors such as size, intensity, and motion play a crucial role in determining what attracts attention. ● Large, bright, and moving stimuli tend to capture our focus easily. ● Novel and moderately complex stimuli also draw our attention. For instance, human faces are more likely to be noticed compared to inanimate objects. ● Additionally, rhythmic auditory cues are more attended to than verbal information. ● Sudden and intense stimuli have a remarkable ability to grab attention.
➔ Internal Factors: These factors lie within the individual. These may be divided into two main categories.
● Motivational Factors: These factors are linked to biological or social needs. For example, when hungry, individuals become highly sensitive to even a faint aroma of food.
● Cognitive Factors: This category includes aspects like interest, attitude, and preparatory set. Individuals are naturally drawn to objects or events that pique their interest.
Theories of Selective Attention
1. FILTER THEORY
● Filter theory was developed by Broadbent (1956). ● According to this theory, many stimuli simultaneously enter our receptors creating a kind of "bottleneck" situation. ● They enter the selective filter, which allows only one stimulus to pass through for higher levels of processing. ● Other stimuli are screened out at that moment of time. ● Thus, we become aware of only that stimulus, which gets access through the selective filter.
2. FILTER - ATTENUATION THEORY
● Filter-attenuation theory was developed by Triesman (1962) by modifying Broadbent's theory. ● This theory proposes that the stimuli not getting access to the selective filter at a given moment of time are not completely blocked. ● The filter only attenuates (weakens) their strength. ● It is indicated that personally relevant stimuli (e.g., one’s name in a collective dinner) can be noticed even at a very low level of sound. Such stimuli, even though fairly weak, may also generate response occasionally by slipping through the selective filter.
Perceptual Processes
The process by which we recognise, interpret or give meaning to the information provided by sense organs is called perception.
● It involves recognizing, interpreting, and constructing stimuli or events based on our learning, memory, motivation, and emotions. ● Perception is not just an objective interpretation of the external or internal world but also a subjective construction based on our individual perspectives.
Processing Approaches in Perception
Recognition of objects can occur through bottom-up or top-down processing.
● Bottom-Up Processing: This approach suggests that recognition begins with identifying the parts of an object first before recognizing the whole.
The bottom-up approach lays emphasis on the features of stimuli in perception, and considers perception as a process of mental construction.
● Top-Down Processing: In contrast, the recognition process begins from the whole, which leads to identification of its various components is known as top-down processing.
The top-down approach lays emphasis on the perceiver, and considers perception as a process of recognition or identification of stimuli.
Studies indicate that both processes interact to help us understand the world around us.
The Perceiver
● Human beings are active recipients in interpreting the world around them. ● Perception is influenced by motivations, expectations, cultural background, past experiences, memories, values, beliefs, and attitudes.
➔ Motivation ● Perception is strongly influenced by the needs and desires of the perceiver.
● For example, hungry individuals are more likely to perceive ambiguous images as food-related compared to non-hungry individuals.
➔ Expectations or Perceptual Sets ● Expectations about what one might perceive in a given situation can significantly influence perception. ● This phenomenon of perceptual familiarisation or perceptual generalisation reflects a strong tendency to see what we expect to see even when the results do not accurately reflect external reality. ● For instance, if the milkman usually delivers milk at 5:30 AM, any knock on the door around that time might be perceived as the milkman's arrival.
➔ Cognitive Styles ● Cognitive style refers to how individuals consistently interact with their environment , affecting perception.
These cognitive styles are mainly divided in two types-
● Field-dependent - Field dependent people perceive the external world in its totality, i.e. in a global or holistic manner. ● Field-independent people perceive the external world by breaking it into smaller units, i.e. in an analytic or differentiated manner.
➔ Cultural Background and Experiences ● Individuals' cultural backgrounds, experiences and learning opportunities available in different cultural settings influence their perception. ● People coming from a pictureless environment fail to recognise objects in pictures. ● For example, Hudson studied the perception of pictures by African subjects, and noted several difficulties. Many of them were unable to identify objects depicted in pictures (e.g., antelope, spear). They also failed to perceive distance in pictures, and interpreted pictures incorrectly. ● Eskimos have been found to make fine distinctions among a variety of snow that we may be unable to notice.
These factors demonstrate that-
- The perceiver plays a key role in the process of perception.
- People process and interpret stimuli in their own ways depending on their personal, social and cultural conditions.
- Due to these factors our perceptions are not only finely tuned, but also modified.
Principles of Perceptual Organisation
The Gestalt psychologists have given us several laws to explain how and why different stimuli in our visual field are organised into meaningful whole objects.
Principles of Gestalt Psychologists
- The Principle Of Proximity : According to this principle, the objects that are close together in space or time are perceived together or as a group. For example, the figure does not look like a square pattern of dots, but as a series of columns of dots.
- The Principle Of Similarity : According to this principle, objects that are similar to one another and have similar characteristics are perceived as a group
- The Principle Of Continuity : This principle states that we tend to perceive objects as belonging together if they appear to form a continuous pattern.
For example, we are more likely to identify two lines a-b and c- d crossing than to identify four lines meeting at the center p.
- The Principle Of Smallness : As per this principle, smaller areas tend to be seen as figures against a larger background.
We are more likely to see a black cross rather than a white cross within the circle because of this principle
- The Principle Of Symmetry : This principle suggests that symmetrical areas tend to be seen as figures against asymmetrical backgrounds
For example, the black areas are seen as figures (as they have symmetrical properties) against their white asymmetrical background.
- The Principle Of Surroundedness : This principle suggests that areas surrounded by others tend to be perceived as figures.
For example, the image looks like four figures against the white background rather than the word ‘TIE’.
- The Principle Of Closure : We tend to fill gaps in stimulation and tend to perceive objects as a whole rather than their separate parts.
The small angles are seen as a triangle due to our tendency to fill the gaps in the object provided by our sensory input.
Linear perspective: distant objects appear closer together than nearer objects. For example, parallel lines, such as rail tracks, appear to converge with increasing distance with a vanishing point at the horizon. The more the lines converge, the farther away they appear.
Aerial perspective: the haze or blur caused by dust and moisture in the air makes distant objects appear farther away. For example, distant mountains appear blue due to the scattering of blue light in the atmosphere, whereas the same mountains are perceived to be closer when the atmosphere is clear.
Light and shade: In the light some parts of the object get highlighted, whereas some parts become darker. Highlights and shadows provide us with information about an object’s distance.
Relative height: larger objects are perceived as closer, while smaller objects are perceived as farther away.
Texture gradient: the density of visual elements in a scene can indicate distance.
Motion parallax: It is a kinetic monocular cue, and hence not considered as a pictorial cue.
When objects at different distances move, they move at different speeds relative to the observer, providing a cue for depth perception.
b. Binocular Cues (Physiological Cues)
Some important cues to depth perception in three dimensional space are provided by both the eyes.
1. Retinal or Binocular Disparity ● Due to the horizontal separation of our eyes (about 6.5 cm), each eye forms a slightly different image of the same object. This difference between the two images is called retinal disparity. ● Retinal disparity occurs because the two eyes have different locations in our head. ● The brain uses the difference between these images to judge depth, - with a larger disparity indicating a closer object and
- a smaller disparity indicating a distant object. 2. Convergence ● When focusing on a nearby object, our eyes turn inward (converge) to align the image on the retina. ● A group of muscles send messages to the brain regarding the degree to which eyes are turning inward ● The brain interprets the degree of convergence as a cue for depth, with increased convergence indicating a closer object and decreased convergence indicating a farther object. 3. Accommodation ● Accommodation refers to a process by which we focus the image on the retina with the help of ciliary muscles adjusting the thickness of the eye's lens to focus on objects at varying distances. ● If the object gets away (more than 2 meters), the muscle is relaxed. As the object moves nearer, the muscle contracts and the thickness of the lens increases. ● The brain receives signals about the degree of muscle contraction to determine the distance of the object.
Perceptual Constancies
Perceptual constancy refers to the ability to perceive objects in a relatively stable manner, even when there are changes in the stimulation of sensory receptors.
Types of Perceptual Constancies:
- Size constancy- The constancy whereby the perceived size of objects remains relatively unchanged with changes in their distance from the observer and the size of the retinal image is called size constancy.
For example, when you approach your friend from a distance, your perception of the friend’s size does not change much despite the fact that the retinal image (image on retina) becomes larger.
- Shape constancy- is the perceptual phenomenon where the perceived shape of familiar objects remains unchanged, even when there are variations in the orientation of the objects that create differences in the pattern of the retinal image.
For example, a dinner plate looks the same shape whether the image that it casts on the retina is a circle, or an ellipse, or roughly a short line (if the plate is viewed from the edge). It is also called form constancy.
● When we see moving pictures in a cinema show, we are influenced by this kind of illusion. ● The succession of flickering electrical lights also generates this illusion.
Experience of illusions indicates that people do not always perceive the world as it is; instead they engage in its construction, sometimes based on the features of stimuli and sometimes based on their experiences in a given environment.
Social Cultural Influences on Perception
● Psychologists study perception across different sociocultural settings to understand whether perceptual processes are uniform or vary by culture. ● Studies using illusion figures (e.g., Muller-Lyer, Vertical-Horizontal) show that different cultural groups have varying susceptibility to these illusions, with Africans being more susceptible to the horizontal-vertical illusion and Westerners to the Muller-Lyer illusion. ● Research by Segall, Campbell, and Herskovits revealed that environmental factors influence perceptual tendencies: Africans in dense forests tend to overestimate vertical lines, while Westerners in right-angled environments tend to underestimate lines with arrowheads. ● Hudson's study found that people with minimal exposure to pictures struggled with object recognition and depth cues, indicating that familiarity and instruction are crucial for effective pictorial perception. ● Sinha and Mishra's research highlights that cultural experiences influence how people interpret pictures. Individuals with less exposure to pictorial media face difficulties in understanding actions or events depicted in images.
