1. Types of Attention: Selective attention and Divided attention
  2. Theories of Attention: (a) Theories of Selective Attention: Broadbent’s model & Triesmann’s model, (b) Theories of Divided Attention: Kahneman’s model
  3. Perceptual Processes: Perception: Meaning and Definition
  4. Gestalt laws of Perceptual Organisation
  5. Depth Perception: Monocular and Binocular cues for depth perception
  6. Constancy: Size Constancy, Brightness Constancy
  7. Movement Perception: Real and Apparent Motion
  8. Visual illusions: Muller-Lyer Illusion, Moon Illusion
  9. Extra Sensory Perception



[! QUESTION] What is Attention? Attention is a cognitive process of selectively concentrating on a discrete aspect of information, whether considered subjective or objective, while ignoring other perceivable information

[! TLDR] TLDR; Concentrating on one task while ignoring other stimuli (filtering) Prioritize stimuli based on goals and needs

Factors Affecting Attention

Internal aka subjectiveExternal
Mental SetSize
Past ExpContrast
Meaningfulness of


MMM, PIE AH? Internal CRIMSoN NL External

Internal Factors

AKA Subjective factors. Depend from person to person.

  1. Interest |
  2. Motive | basic needs and motives > other ones; what we want to do; task at hand
  3. Mental Set | readiness to respond; expecting a stimulus
  4. Past Experiences |
  5. Emotions |
  6. Habits |
  7. Aim |
  8. Organic state| Hunger, sleep, etc

External Factors

  1. Nature | Pic >>> Words
  2. Intensity | Louder >> Softer
  3. Size | Larger >> Smaller
  4. Repetition | More times >> Less times
  5. Contrast | Stark difference, can be in colours or concepts
  6. Novelty | Something new, out of place
  7. Location | Center >> other places
  8. Movement | Moving >> Static

Types of Attention

1. Based on Needs

a) Sustained Attention it is the ability to pay attention to only one task by consciously concentrating on that task only for a long time enough and by avoiding all other forms of distractions or deviations. Eg - reading a book, memorizing a chapter or following a classroom lecture.

b) Selective Attention: In this case, the listener chooses to pay attention to only a specific stimulus which is present in the environment while ignoring the other stimuli. This kind of attention does not depend on the stimulus but depends essentially on the attentive capabilities of an observer. Choosing to focus on a friend’s voice (while in a crowd with them)

c) Divided Attention: In case of divided attention, the user pays attention to two or more tasks at the same time and is also sometimes regarded as Multi-tasking which involves juggling between two or more than two tasks at the same time. Divided attention uses a lot of mental focus; ergo person may get exhausted very quickly. Function is impaired. Split our attention

d) Alternating Attention: Though this attention can be closely related to divided attention, but is different as in case of divided attention we split our attention between two tasks, while in case of alternating attention, the entire attention is shifted from one task to another or is done alternately.

2. Based on Volition

a) Voluntary (aka volitional) requires will and determination not spontaneous conscious effort goal based eg - doing math

b) Involuntary (aka non-volitional) does not involve any role of will instinctual spontaneous enforced attention eg - mom hearing baby

Auditory - ability to pay attention to auditory stimuli, related to temporal Visual - visual stimuli, related to spatial

Models Of Attention


1. Broadbent’s Model of Selective Attention | Early Selection Theory

graph LR

one[Attended Stimuli]--> A

two[Unattended Stimuli]--> A

A[Sensory Register] --Attended--> B(Selective Filter)

L[Selective filter removes <br> the unattended stimuli <br> completely]


B --> |Bottleneck| C(Working Memory)

C --> D(Other Cognitive Functions)

All stimuli is registered in the sensory register, and then they go through the selective filter which filters out based on physical characteristics After selective filter, meaning is assigned to the stimuli and then processed

selection of stimuli for processing occurs before stimulus identification (Early Selection)

Bottleneck theory - individuals have a limited amount of attentional resources that they can use at one time

2. Treisman’s Model | Attenuation Theory

Attenuation - the lessening or weakening in the intensity, value, or quality of a stimulus

unattended messages are attenuated or processed weakly but not entirely blocked from further processing Thus, a significant word (e.g., the person’s name) would have a low threshold and, when mentioned, would be recognized even if that person’s attention is concentrated elsewhere (Cocktail Party Effect)

graph LR

one[Attended <br> Stimuli]--> A

two[Unattended <br> Stimuli]--> A

A[Sensory <br> Register] --Attended--> B(Attenuator)

L[Attenuator weakens <br> the stimuli and <br> sends it to the <br> dictionary unit] 


B --> |Attended| C(Dictionary <br> Unit)

B -.-> |Weakened <br> Unattended| C

C --> D(Other Cognitive Functions)

style L fill:#ebccff;


3. Kahneman’s Model

Daniel Kahneman Attention is scarce. Some tasks require more, some less. We can do multiple tasks at once as long as it is within the capacity of attention. mental “juggling” mental efforts total available processing capacities depends on arousal and other factors Central Allocation Policy

You can do several things at once, but only if they are easy and undemanding. More than once as long as it is within the processing capacity available

Easy or diff Similarity of tasks Practice

graph RL

1[Inputs]--> A
A[Arousal] --> B(Central <br> Processor)

B --> C(Evaluation of demand)

C --> R(Response)

subgraph three [Allocation of Resources]

ed[Enduring Disposition / Automatic ]

mi[Momentary Intention]  

ed --> B

mi --> B


m[Attentional Capacity depends on arousal]
C --> A
C --> B

Interference is the term used to describe when a
person has a hard time attending to two stimuli at a
time. We see interference when the brain is only able
to process a certain amount of information

Momentary intention:

A conscious decision to
allocate attention to certain aspects of the

Enduring Disposition

An automatic influence where people direct their attention.

Summary of Models

ModelAKAPrincipleMain Component
Broadbent’s TheoryEarly SelectionBased on physical properties, filtered out before identification, bottleneck theoryselective filter
Treisman’s TheoryAttenuation TheoryBased on threshold, unattended stimuli is weakened but processes, cocktail partyattenuator, dictionary unit
Kahneman’s TheoryDivided AttentionCan do multiple things at once depending on capacity; Central Allocation Policy; IMEcentral processor

Broadbent, Treisman Selective Attention Theory Kahneman Divided Attention Theory

Broadbent said that filtered out by physical properties, semantic analyis is not done, meaning is not assigned to unattended stimuli,

Sensory Register Selective Filter Working Memory Other Cog functions

Treisman signal is weakened, everything is processed, some words have lower thresholds than others, CPE

Sensory Register Attenuator Dictionary Unit Other Cog functions

Kahneman CAP, can attend to multiple stimuli, each task requires diff amount of effort

Arousal Central Processing Unit Evaluation of demand Response --------------------| -------------------- Momentary Intention - (Allocation -------------------- Enduring Disposition - of resources)


Definition - the organization, identification, and
interpretation of sensory information
represent and understand the environment.

Sensation: the process by which our sense organs
receive information from the environment.

we gain information about the properties and elements of the environment helps us navigate and understand the world around us helps us interact w environment helps us survive

Psychophysics is the study of the relationship between the physical aspects of stimuli and our psychological experience of them

Senses - (five senses) proprioception social cues

Absolute threshold: the smallest intensity of
the stimulus that must be present for it to be

Difference threshold: the smallest level of
stimulation required to sense that a change has

Just noticeable difference: The minimum
stimulation required to detect the difference
between the two stimuli.

Adaptation: An adjustment in sensory capacity
following prolonged exposure to stimuli.

top-down processing Perception that is guided by higher-level knowledge, experience, expectations, and motivations

bottom-up processing Perception that consists of the progression of recognizing and processing information from individual components of a stimuli and moving to the perception of the whole.

Gestalt Laws of Perceptual Organisation


a misrepresentation of a “real” sensory stimulus an interpretation that contradicts objective “reality” as defined by general agreement universal unlike hallucinations real stimuli, wrong interpretation

Monocular and Binocular Cues

flowchart TD

Depth[Depth Perception] ---> a[monocular] & b[binocular]


n[the visual ability to perceive <br> world in 3D <br> ability to gauge <br> how far an object is ]


a --- d[one eye] --- f[bad at depth]

b --- e[two eyes] --- h[diff angles helps]


n --- m[relies on the convergence <br>  of both eyes upon a <br> single object]

m --- x[navigating, determing dist, <br> avoiding, etc]

lateral displacement of the eyes that provides
two slightly different views of the same object allowing STEREOPSIS / two images which helps us discern depth better

Mono CuesBino Cues
Relative Size
size constancy - smaller = far
Retinal Disparity
Overlapping objects, object that overlaps = closer
Binocular Convergence
Linear Perspective
converging of parallel lines
scattering of blue light; far hill appears blue
closer hill more contrast
Light and Shade
Highlights and shadows help us understand dimensions
of object, where light is coming from, etc
Ponzo Illusion

Perceptual constancy refers to the tendency to perceive an object you
are familiar with as having a constant shape, size, and brightness e.g. - moon illusion

Size Const. Shape Const. Colour Const.

Real and Apparent motion

Apparent Motion -

  • Phi Phenomena - bulbs in row, flashing, feels like moving • Motion after effect (MAE)
    • Induced motion - train moving next to you, you feel like you are moving • Autokinetic movement - dark room, singular light, feels like moving