Cognition Lecture 2/20

Visual System and Feature Integration Theory

• Visual Processing Overview

  • Visual system assesses images and objects through distinct features.

  • Features include motion, orientation, color, and shape.

  • Focused attention is necessary to combine these features into coherent objects.

• Role of Focused Attention

  • Focused attention is conceptualized as "registration" of features.

  • Different feature maps (shape, orientation, color) are correlated through attention.

  • This combining process creates a unified perception of objects with multiple attributes.

Philosophical Context

• Connection to Western Philosophy

  • Theory relates to Aristotelian and British empiricist thought (Locke, Berkeley, Hume).

  • Philosophers explored the relationship between objects and their features.

• Neural Mechanism

  • The theory proposes a neural basis for how features are processed in early vision.

  • Brightness (luminance) is separated from color signals in motion perception.

Singleton Search Paradigm

• Definition and Purpose

  • Developed by Anne Treisman as a methodology to study visual attention.

  • Involves presenting a display with multiple items, where only one target (singleton) might be present.

  • Focus is on measuring reaction times to determine processing times.

• Phase One Technology

  • technology aims for data that is clear and interpretable regarding mind and visual processing.

  • Investigates how quickly and accurately subjects can detect targets.

• Research Goals

  • To understand the mechanics of visual search and attention.

  • Identify how many elements (set size) impact reaction times in detecting targets.

Reaction Times and Search Strategies

• Search Strategy Types

  • Pop-out Searches: Certain targets immediately stand out, requiring minimal attention.

  • Conjunction Searches: Targets require integration of multiple features, demanding focused attention.

• Set Size Impact

  • Reaction time increases with set size in conjunction searches since it requires more focused attention and searching.

  • Sequential examining of potential targets leads to longer reaction times.

Parallel and Serial Processing

• Serial vs. Parallel Processing

  • Serial Processing: Observing one object at a time, leading to longer response times as set size increases.

  • Parallel Processing: Multiple items can be processed simultaneously, relevant in pop-out tasks.

  • Distinction helps in understanding cognitive load and how attentional resources are allocated.

• Expert Overview

  • Even with expertise, quick visual identification of pop-out targets doesn’t negate the necessity of focused attention in conjunction searches.

Probability and Reaction Time Analysis

• Trial Analysis

  • Distinction between "target present" and "target absent" trials.

  • Reaction times vary based on whether subjects are sure a target exists or if they must verify presence.

• Statistical Interpretation

  • Focuses on the average performance across multiple trials to minimize outliers and errors.

  • Distribution of reaction times observed during psychophysical experiments; high variability in responses.

Limitations and Challenges**

• Cognitive Load Concerns

  • Reaction times must be reasonable: typically not expected to exceed 1 to 1.5 seconds under optimal conditions.

  • Long reaction times may indicate lapses in attention or other cognitive effects.

• Data Variability

  • Interpretation of data can be inconsistent, depending on experimental context and participant engagement levels.

Future of Visual Attention Research**

• Technology Developments

  • Improvements in methodologies are necessary to better understand attention processes.

  • Need for more refined technologies to test hypotheses effectively.

• Theories in Flux

  • Current theories may need adjustments based on new findings and technological advancements.

  • Importance of repeated experiments and accumulated data for refining theories in psychology.