Chapter 7: Attention and Scene Perception

Attention

Any of the very large set of selective processes in the brain.

- To deal with the impossibility of handling all inputs at once, the nervous system has evolved mechanisms that are able to restrict processing to a subset of things, places, ideas, or moments in time.

Types of Attention (not mutually exclusive) - Selective attention

The form of attention involved when processing is restricted to a subset of the possible stimuli.

- External: Attending to stimuli in the world.

- Internal: Attending to one line of thought over another or selecting one response over another.

- Overt: Directing a sense organ toward a stimulus, like turning your eyes or your head.

- Covert: Attending without giving an outward sign you are doing so.

- Divided: Splitting attention between two different stimuli.

- Sustained (vigilance): Continuously monitoring some stimulus.

Inattentional blindness

A failure to notice—or at least to report—a stimulus that would be easily reportable if it were attended.

Change blindness

The failure to notice a change between two scenes.

Bottom-up and Top-down Processing

• Bottom-up processing

- Automatic, stimulus-driven

• Top-down processing

- Controlled, goal-driven Interaction

- Working together in complementary roles

Reaction time (RT)

A measure of the time from the onset of a stimulus to a response.

Cue

A stimulus that might indicate where (or what) a subsequent stimulus will be.

- Cues can be valid (correct information), invalid (incorrect), or neutral (uninformative).

Stimulus onset asynchrony (SOA)

The time between the onset of one stimulus and the onset of another.

Theories of Attention

- "Spotlight" model: Attention is restricted in space and moves from one point to the next. Areas within the spotlight receive extra processing.

- "Zoom lens" model: The attended region can grow or shrink depending on the size of the area to be processed.

Visual search

Looking for a target in a display containing distracting elements.

Guided search

Attention is restricted to a subset of possible items based on information about the item's basic features (e.g., color or shape).

Inhibition of return (IOR)

The relative difficulty in getting attention (or the eyes) to move back to a recently attended (or fixated) location.

- During searches, stops you from getting stuck continually revisiting one spot.

Serial self-terminating search

A search from item to item, ending when a target is found.

Feature search

(efficient) Search for a target defined by a single attribute, such as a salient color or orientation.

• Salience: The vividness of a stimulus relative to its neighbors.

• Parallel: In visual attention, referring to the processing of multiple stimuli at the same time.

Conjunction search

Search for a target defined by the presence of two or more attributes.

Scene-based guidance

Information in our understanding of scenes that helps us find specific objects in scenes.

The binding problem

The challenge of tying different attributes of visual stimuli, which are handled by different brain circuits, to the appropriate object so we perceive a unified object.

Feature integration theory

(Anne Treisman) - a limited set of basic features can be processed in parallel preattentively, but that other properties, including the correct binding of features to objects, require attention.

Preattentive stage

The processing of a stimulus that occurs before selective attention is deployed to that stimulus.

Illusory conjunction

An erroneous (wrong) combination of two features in a visual scene.

Rapid serial visual presentation (RSVP)

An experimental procedure in which stimuli appear in a stream at one location (typically the point of fixation) at a rapid rate (typically about eight per second).

- is used to study the temporal dynamics of visual attention.

Attentional blink

The difficulty in perceiving and responding to the second of two target stimuli amid a RSVP stream of distracting stimuli.

Three ways responses of a cell could be changed by attention

1. Response enhancement

2. Sharper tuning

3. Altered tuning

Visual-field defect

A portion of the visual field with no vision or with abnormal vision, typically resulting from damage to the visual nervous system.

- Damage to the parietal lobe can cause this, such that one side of the world is not attended to.

Neglect

In visual attention, the inability to attend to or respond to stimuli in the contralesional visual field.

- Typically, neglect of the left visual field after damage to the right parietal lobe

Selective pathway

Permits the recognition of one or a very few objects at a time. This pathway passes through the bottleneck of selective attention.

Nonselective pathway

Contributes information about the distribution of features across a scene as well as information about the "gist" of the scene. This pathway does not pass through the bottleneck of attention.

Ensemble statistics

The average and distribution of properties, such as orientation or color, over a set of objects or a region in a scene.

Spatial layout

The description of the structure of a scene (e.g., enclosed, open, rough, smooth) without reference to the identity of specific objects in the scene.

Altered tuning

that attention changes the preferences of a neuron

Anchor objects

relatively big objects in predictable locations that tell you about the location of other objects. (EX: Sinks)

Balint syndrome

a disorder where everything except the current object of attention seems to be blocked from conscious perception

Contralesional field

the field on the side opposite the lesion. Where patients draw only half a circle or half a house.

Ipsilesional field

the same side as the lesion.

Endogenous cue

The symbolic cue (the red dot) is an example

Exogenous cue

The peripheral cue (the outlined box) is an example

Parallel search

we can process the color or orientation of all the items at once

Peripersonal space

that part of the world that is near your body, especially your hands.

Salient

If it stands out visually from its neighbors.