UNIT-3 Attention and Perception

Definition
 According to the APA Dictionary of Psychology (2023), attention is defined as “a
state of focused awareness on a subset of the available perceptual information”
(APA, 2023).
 William James (1890, Principles of Psychology) gave a classic definition: “Everyone
knows what attention is. It is the taking possession by the mind, in clear and vivid
form, of one out of what seem several simultaneously possible objects or trains of
thought.”
 In simple terms: Attention is the selective allocation of mental resources toward
certain stimuli or tasks, allowing deeper processing and response.
Perception
Definition
 The APA Dictionary of Psychology (2023) defines perception as:
“The process or result of becoming aware of objects, relationships, and events by
means of the senses, which includes such activities as recognizing, observing, and
discriminating.”
 In simple terms, perception is the cognitive process through which we interpret and
organize sensory input, transforming raw sensory data into meaningful information
about the world.

Difference Between Attention and Perception

Aspect Attention Perception
Selective focusing of mental Process of interpreting and organizing sensory
Definition
processes on specific stimuli. input into meaningful experiences.
Constructs coherent awareness from raw
Function Acts as a filter or gatekeeper.
sensory data.
Level Higher-order control process. Early stage of cognition (input analysis).
Focusing on one friend’s voice in Recognizing that the sound you hear is your
Example
a noisy party. friend’s voice.
Attention influences what is Perception provides the raw material for
Relation
perceived more clearly. attention to act on.

Types of Attention
1. Sustained Attention (Vigilance)
  The ability to maintain focus on a task or stimulus over an extended period.
 Important for activities like reading, monitoring radar screens, or long driving.
 Example: An air-traffic controller watching the radar for hours.

2. Selective Attention
 Focusing on one stimulus or task while ignoring competing stimuli.
 Classic demonstration: Cocktail Party Effect – hearing your name in a noisy room.
 Theories: Broadbent’s filter model, Treisman’s attenuation, Deutsch–Norman late
selection.

3. Divided Attention
 Ability to attend to two or more tasks simultaneously.
 Performance depends on task complexity and practice.
 Example: Driving while listening to music.
 Resource model (Kahneman, 1973) explains limitations.

4. Alternating Attention (Shifting Attention)

 The capacity to switch focus between different tasks or stimuli.
 Involves cognitive flexibility.
 Example: A student shifting between listening to lecture and taking notes.

5. Focused Attention
 The most basic form – responding to a particular sensory stimulus.
 Involves orienting toward a sound, light, or touch.
 Often tested in clinical/neuropsychological assessments.

6. Executive Attention
 Involves control of thought and behavior, resolving conflicts, inhibiting
distractions.
 Strongly linked to the anterior cingulate cortex and prefrontal areas.
  Example: Staying focused on solving a math problem despite phone notifications.
Types of Perception
 Visual perception – recognizing objects, depth, color, motion.
 Auditory perception – speech, music, sounds.
 Tactile perception – touch, pressure, texture.
 Olfactory & gustatory perception – smell and taste.
 Multisensory perception – integration across senses (e.g., McGurk effect in speech
perception).

Factors Influencing Attention

1. External (Stimulus-driven) factors
o Intensity (bright light, loud sound)

o Novelty (new or unusual stimuli capture attention)

o Movement (moving objects attract more attention)

o Contrast (figure-ground differences)

o Repetition (frequent exposure can maintain attention)

2. Internal (Organism-driven) factors

o Motivation & Needs (a hungry person notices food-related cues faster)

o Emotional state (fear, anxiety can narrow focus)

o Expectancy & Past experience (knowledge guides what we notice)

o Interest (personal relevance improves attention span)

Theories of Attention
Bottleneck Theories
Definition
 Bottleneck theories suggest that because the human information-processing system
has limited capacity, only a small amount of sensory input can be processed at
higher cognitive levels.
 The “bottleneck” is a narrow point in the flow of information, where selection
occurs.

1. Broadbent’s Filter Model (1958) – Early Selection Theory

 Concept:
o All sensory information enters a sensory buffer.

o A filter selects input for further processing based on physical characteristics

(e.g., ear, pitch, loudness).
o Unattended information is blocked completely.

 Evidence:
o Dichotic listening task → Participants recall words from the attended ear but
not the unattended one.
 Strengths: First systematic model of selective attention; explains focus in noisy
settings.
 Limitations: Cannot explain why some unattended information (like one’s name) still
breaks through (Cocktail Party Effect).
2. Treisman’s Attenuation Model (1964) – Modified Early Selection
 Concept:
o Instead of blocking unattended messages, the filter attenuates (weakens)
them.
o Meaningful or high-priority information (e.g., name, danger signals) can cross
the threshold of awareness.
 Evidence:
o In dichotic listening, participants sometimes notice unattended words (e.g.,
their own name).
 Strengths: Explains why some unattended stimuli reach awareness.
 Limitations: Doesn’t fully explain how all semantic processing occurs.

3. Deutsch & Deutsch (1963) and Norman’s Late Selection Theory (1968)
 Concept:
o All incoming stimuli are processed for meaning.

o Selection (the “bottleneck”) occurs after semantic analysis, just before

response.
 o Attention decides which meaning enters consciousness or guides behavior.

 Evidence:
o Stroop effect → both word meaning and ink color are processed, but selection
happens late.
 Strengths: Explains processing of unattended meaningful info.
 Limitations: Implies the brain processes everything fully, which is energy-demanding
and unlikely.

Automatic vs Controlled Processing

(Schneider & Shiffrin, 1977)
 Controlled processes: conscious, effortful, flexible, slow (e.g., learning to drive).
 Automatic processes: unconscious, fast, inflexible, develop with practice (e.g.,
skilled reading).
 Stroop Effect demonstrates conflict between automatic (reading) and controlled (color
naming) processing.

Cognitive Neuroscience of Attention

Major Attention Networks in the Brain
1. Posterior Attention Network (Orienting System)
  Location: Parietal lobe (especially posterior parietal cortex), superior colliculus
(midbrain), pulvinar (thalamus).
 Function:
o Shifts and orients attention to external sensory stimuli.

o “Where” pathway – spatial orienting of visual attention.

 Posner & Petersen (1990):

o Disengage attention → parietal lobe.

o Move attention → superior colliculus.

o Engage attention → pulvinar nucleus of thalamus.

 Disorders: Damage causes unilateral neglect (ignoring one side of space).

2. Anterior Attention Network (Executive Control System)

 Location: Dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC),
basal ganglia.
 Function:
o Executive control of attention.

o Conflict resolution (e.g., Stroop task).

o Inhibition of irrelevant responses.

 Role in Working Memory: Helps sustain attention during problem-solving.

 Clinical Links: Dysfunction seen in ADHD, schizophrenia, depression, where
executive control is impaired.

3. Reticular Activating System (RAS) – Arousal/Vigilance Network

 Location: Brainstem (reticular formation), thalamus, hypothalamus.
 Function:
o Maintains alertness, arousal, and sustained attention.

o Regulates transitions between sleep and wakefulness.

 Neurochemistry:
o Norepinephrine (from locus coeruleus) → vigilance.

o Dopamine → motivation and reward-based attention.

 o Acetylcholine → cortical activation for attention.

 Clinical Links: Lesions cause coma or drowsiness.

Additional Brain Areas Involved
 Frontal eye fields (FEF): Voluntary control of eye movements and visual attention.
 Superior colliculus: Rapid, automatic orienting to visual/auditory stimuli.
 Thalamus (pulvinar): Gatekeeper, helps filter irrelevant input.
 Parietal cortex (especially right hemisphere): Directs attention across visual space.

Neuroimaging and Experimental Evidence

 fMRI & PET scans show distinct activation patterns for different types of attention:
o Selective attention: Increased activity in occipital and parietal regions when
focusing on visual stimuli.
o Divided attention: Dorsolateral prefrontal cortex and ACC show high activity
during multitasking.
o Sustained attention (vigilance): Right frontal and parietal areas remain active
over time.
 ERP studies (Event-Related Potentials):
o P300 component reflects attentional resource allocation.

 Single-cell recordings (monkeys): Cells in parietal and frontal cortex fire more
strongly when attention is directed to their receptive field.

Key Models
 Posner & Petersen (1990) – Attention Networks Framework:
1. Alerting Network (arousal, vigilance) → locus coeruleus, frontal/parietal
regions.
2. Orienting Network (directing attention) → parietal cortex, superior colliculus,
pulvinar.
3. Executive Network (control, conflict monitoring) → ACC, DLPFC, basal
ganglia.
 Corbetta & Shulman (2002) – Dorsal vs Ventral Attention Systems:
o Dorsal system (goal-directed, top-down): Intraparietal sulcus, frontal eye
fields.
 o Ventral system (stimulus-driven, bottom-up): Temporoparietal junction,
ventral frontal cortex (especially right hemisphere).
o Explains balance between voluntary and automatic attention shifts.

Clinical Relevance
 ADHD: Reduced activity in anterior attention/executive networks.
 Unilateral neglect: Damage to right parietal lobe → failure to orient to contralateral
side.
 Schizophrenia: Impaired executive control and filtering of irrelevant information.
 Parkinson’s disease: Deficits in basal ganglia impair attentional shifting.

Posner’s Theory of Neural Bases of Attention

Background
 Developed by Michael Posner (1980, 1990) through experiments using the “spatial
cueing paradigm.”
 His work showed that attention can shift independently of eye movements (covert
attention).
 Demonstrated that attention enhances information processing like a “spotlight” that
can be directed to different regions of space.

The Spatial Cueing Task (Posner, 1980)

 Participants fixate at center of a screen.
 A cue (arrow or flash) indicates where a target is likely to appear.
 Reaction times (RTs) to detect the target are measured.
Findings:
 RTs are faster when cue correctly predicts the target location (valid trials).
 RTs are slower when cue misleads (invalid trials).
 RTs are intermediate for neutral cues.
👉 Conclusion: Attention acts as a spotlight, improving processing in cued locations.

Posner’s Three Stages of Attentional Orienting

Posner proposed that orienting attention involves three distinct processes:
1. Disengage attention from current focus.
o Brain area: Posterior parietal lobe.

o Damage → patients with parietal lesions (esp. right hemisphere) show spatial
neglect (cannot disengage from one side).
2. Move attention to new location.
o Brain area: Superior colliculus (midbrain).

o Important for initiating attentional shifts and eye movements.

3. Engage attention on the new stimulus.

o Brain area: Pulvinar nucleus of thalamus.

o Enhances processing of selected input and suppresses irrelevant information.

Types of Attention in Posner’s Framework

1. Exogenous (stimulus-driven, bottom-up):
o Attention automatically captured by external events (e.g., sudden flash).

o Involves ventral attention system (right temporoparietal junction).

2. Endogenous (goal-directed, top-down):

o Attention guided voluntarily according to goals (e.g., searching for a friend in
crowd).
o Involves dorsal attention system (intraparietal sulcus, frontal eye fields).

Neural Networks Identified by Posner & Petersen (1990)

 Alerting Network:
o Maintains arousal and vigilance.

o Neurotransmitter: Norepinephrine (locus coeruleus).

 Orienting Network:
o Directs attention toward sensory stimuli (posterior parietal cortex, superior
colliculus, pulvinar).
 Executive Control Network:
 o Resolves conflicts, inhibits distractions (anterior cingulate cortex, prefrontal
cortex).
o Neurotransmitter: Dopamine.

Disorders of Perception and Attention

1. Synaesthesia
Definition
 According to the APA Dictionary of Psychology (2023), synaesthesia is “a
condition in which stimulation of one sensory modality reliably elicits an involuntary
sensation in another modality.”
 Example: seeing colors when hearing music, or tasting flavors when reading words.
Features
 Automatic (cannot be controlled).
 Consistent (same stimulus always evokes same additional perception).
 Cross-modal (between senses).
Neural Basis
 Cross-activation between sensory brain regions (e.g., color area V4 and grapheme
recognition areas).
 Excess connectivity between regions that are usually distinct.
Clinical Relevance
 Not considered a disorder in a harmful sense — often enhances creativity (famous
synaesthetes: Kandinsky, Nabokov).

2. Blindsight
Definition
 Condition where individuals with damage to the primary visual cortex (V1) report
blindness but can respond to visual stimuli without conscious awareness.
Features
 Can detect motion, orientation, or location of stimuli at above-chance levels, despite
saying they “see nothing.”
Neural Basis
  Alternative visual pathways via the superior colliculus and pulvinar bypass
damaged V1.
 Conscious vision requires V1, but unconscious visual processing still occurs.
Clinical Relevance
 Demonstrates distinction between visual sensation and visual awareness.

3. Unilateral Spatial Neglect (Hemispatial Neglect)

Definition
 A disorder of attention (not sensory loss) where patients fail to attend to stimuli on
one side of space, usually the left side.
Features
 Caused by damage to right parietal lobe.
 Patients may:
o Eat food only from right side of plate.

o Shave/make-up only one half of face.

o Deny ownership of their left limbs (anosognosia).

Neural Basis
 Right parietal cortex critical for spatial attention to both sides.
 Damage → left-side neglect.
Clinical Relevance
 Common after stroke (right hemisphere).
 Treated with attention training, prism adaptation.

4. Visual Agnosia
Definition
 Inability to recognize or identify objects despite intact vision.
Types
1. Apperceptive Agnosia
o Cannot form a whole percept from parts.

o Patients cannot copy or match objects.

 o Damage: occipital-temporal pathways.

2. Associative Agnosia
o Perception intact but cannot link to meaning.

o Can copy drawings but cannot name/recognize the object.

o Damage: left occipito-temporal regions.

Neural Basis
 Disruption of ventral visual pathway (“what” pathway).
Clinical Relevance
 Rare, often seen after carbon monoxide poisoning or stroke.

5. Prosopagnosia (Face Blindness)

Definition
 Specific inability to recognize faces, despite normal vision and object recognition.
Features
 Patients cannot recognize familiar faces (even their own reflection).
 Can still use non-facial cues (voice, hair, gait) for identification.
Neural Basis
 Damage to the fusiform face area (FFA) in the inferior temporal lobe (right
hemisphere dominant).
Types
 Acquired prosopagnosia → due to brain injury/stroke.
 Developmental prosopagnosia → present without obvious brain damage.
Clinical Relevance
 Patients often feel socially isolated or embarrassed.
Summary Table

Disorder Definition Brain Area Affected Key Features

Cross-sensory perception Cross-wiring between Automatic, consistent,

Synaesthesia
(e.g., hear colors) sensory areas cross-modal

Respond to visual stimuli V1 lesion, superior “Blind but can see

Blindsight
without awareness colliculus pathway intact unconsciously”

Unilateral Ignore one side of space Eat/shave only one side,

Right parietal lobe
Neglect (usually left) anosognosia

Cannot recognize objects Occipito-temporal Apperceptive vs

Visual Agnosia
despite vision “what” pathway associative types

Fusiform Face Area Can recognize by voice

Prosopagnosia Cannot recognize faces
(FFA), temporal lobe but not face

References
Broadbent, D. E. (1958). Perception and communication. Pergamon Press.
→ (Classic early selection filter theory of attention).
Treisman, A. (1964). Selective attention in man. British Medical Bulletin, 20(1), 12–16.
→ (Introduced attenuation model of attention).
Posner, M. I., & Petersen, S. E. (1990). The attention system of the human brain. Annual
Review of Neuroscience, 13(1), 25–42.
→ (Landmark work on neural bases of attention).
Kahneman, D. (1973). Attention and effort. Prentice Hall.
→ (Explains resource model of attention and mental effort).
Farah, M. J. (2004). Visual agnosia (2nd ed.). MIT Press.
→ (Covers agnosia, prosopagnosia, and perceptual disorders).
Weiskrantz, L. (1986). Blindsight: A case study and implications. Oxford University Press.
→ (Seminal book on blindsight and unconscious vision).