Information Processing

The information processing approach emerged as a revolutionary framework in psychology during the 1950s and 1960s, fundamentally changing how researchers conceptualized mental processes. This chapter explores the historical development of information processing theories and their impact on cognitive psychology.

Four Revolutions and Cognitive Metaphors

The development of information processing psychology was influenced by four major revolutions:

Industrial Revolution: Assembly-Line Metaphor

The assembly-line metaphor suggested that cognitive processes could be understood as a series of sequential stages, each performing specific operations on information before passing it to the next stage.

Technological Revolution: Telephone Metaphor

The telephone system provided a metaphor for understanding how information could be transmitted, processed, and received, introducing concepts of channels, capacity, and interference.

Digital Revolution: Computer Metaphor

Computers offered the most influential metaphor, suggesting that the mind could be understood as an information processing system with inputs, processing units, storage, and outputs.

Cognitive Revolution

These technological metaphors converged to create the cognitive revolution, fundamentally shifting psychology from behaviorist to information processing approaches.

Donders' Processing Stages

The Subtractive Logic

Franciscus Donders (1868) pioneered the measurement of mental processing stages using reaction time methods. His subtractive logic involved:

Figure 7.1a: Simple reaction time

Figure 7.1b: GO-NO GO task

Figure 7.1c: Two-alternative forced choice

1. Simple Reaction Time: Respond to a single stimulus
2. GO-NO GO Task: Respond to one stimulus, withhold response to another
3. Two-Alternative Forced Choice (2AFC): Choose between two different responses

Figure 7.2a: Assembly line metaphor

Figure 7.2b: Task processing stages

Figure 7.3a: Identification time

Figure 7.3b: Reaction time analysis

By subtracting reaction times between conditions, Donders aimed to isolate the time required for specific mental processes like stimulus identification and response selection.

Criticisms and Limitations

Donders' approach faced several criticisms:

• Serial vs. Parallel Processing: Assumed sequential rather than simultaneous processing
• Unpredictable Stages: Mental stages might not be additive
• Task Complexity: Different tasks might engage different processes

Sternberg's Additive-Factors Logic

Saul Sternberg developed an alternative approach using additive-factors logic, examining how different experimental manipulations interact to reveal underlying processing stages.

The Psychological Refractory Period (PRP)

The Psychological Refractory Period (PRP) effect demonstrates the bottleneck in human information processing. When two stimuli are presented in rapid succession, the response to the second stimulus is delayed, suggesting that certain processing stages cannot operate in parallel.

Figure 7.4: PRP effect showing delayed response to second
stimulus

Figure 7.5: Bottleneck model explaining PRP

Key Findings:

• Stimulus Onset Asynchrony (SOA): The time between the first and second stimulus
• PRP Effect: Increased reaction time to the second stimulus at short SOAs
• Bottleneck Theory: Central processing stages create a bottleneck that prevents parallel processing

This finding supported the idea of a single-channel, limited-capacity central processing mechanism.

Cybernetics and the Macy Conferences

The interdisciplinary Macy Conferences (1946-1953) brought together researchers from various fields to discuss cybernetics - the study of control and communication in animals and machines. These conferences were crucial in:

• Establishing information theory as a framework for understanding cognition
• Promoting interdisciplinary collaboration
• Developing concepts of feedback, control systems, and information processing

Shannon's Information Theory

Figure 7.6: Shannon's communication model

Figure 7.7: Information theory framework

The Communication Model

Claude Shannon's mathematical theory of communication provided a quantitative framework for measuring information. His model included:

• Sender: Source of information
• Message: Information to be transmitted
• Channel: Medium of transmission
• Receiver: Destination of information
• Noise: Interference in transmission

Measuring Information in Bits

Shannon introduced the concept of measuring information in binary digits (bits). The amount of information (H) in a message is calculated using:

H = -Σ P(xi) × log₂ P(xi)

Where P(xi) is the probability of each event occurring.

Key Principles

1. Maximum Information: Occurs when events are equally probable and unpredictable
2. Minimum Information: Occurs when events are completely predictable
3. Predictability and Information: More predictable messages carry less information

Examples of Information Calculation

• Four equally probable events: H = 2 bits (maximum uncertainty)
• Unequal probabilities: H < 2 bits (some predictability)
• One certain event: H = 0 bits (no uncertainty)

The Hick-Hyman Law

Choice Reaction Time Research

Choice reaction time tasks involve presenting one of several possible stimuli and requiring participants to make the appropriate response as quickly as possible.

The Discovery

William Hick (1952) and Ray Hyman (1953) independently discovered that reaction time increases linearly with the amount of information (measured in bits) in the stimulus set, not simply with the number of alternatives.

Experimental Design

Hyman's crucial experiment separated the effects of:

• Number of alternatives: How many different stimuli were possible
• Information content: How predictable each stimulus was

Key Findings

1. Linear Relationship: Reaction time increased linearly with information content (bits)
2. Information vs. Alternatives: Information content, not just the number of alternatives, determined reaction time
3. Predictability Effects: More predictable stimuli led to faster responses

The Hick-Hyman Law

Reaction Time = a + b × H

Where:

• a = intercept (baseline processing time)
• b = slope (processing rate)
• H = information content in bits

Implications for Behaviorism

The Hick-Hyman law posed significant challenges to behaviorist theory:

1. Beyond Stimulus-Response: Responses were influenced not just by the presented stimulus, but by the entire set of possible stimuli
2. Expectation Effects: Performance was affected by expectations about what stimuli might appear
3. Mental Operations: The findings implied intervening mental processes between stimulus and response
4. Mathematical Framework: Information theory provided a quantitative approach to studying mental processes

Information Theory and Beyond

Shannon's information theory had profound implications for psychology:

Applications

• Attention Research: Understanding selective attention as information filtering
• Memory Studies: Conceptualizing memory as information storage and retrieval
• Decision Making: Analyzing choices in terms of information processing
• Perception: Understanding sensory processing as information extraction

Limitations and Criticisms

• Semantic Content: Information theory focused on statistical properties, not meaning
• Human vs. Machine: Humans process information differently than machines
• Context Effects: Human information processing is highly context-dependent
• Parallel Processing: Humans can process multiple information streams simultaneously

Legacy and Impact

The information processing approach fundamentally transformed psychology by:

1. Providing Quantitative Methods: Offering mathematical tools for studying mental processes
2. Bridging Disciplines: Connecting psychology with computer science, engineering, and mathematics
3. Enabling Cognitive Psychology: Laying the groundwork for the cognitive revolution
4. Influencing Modern Research: Continuing to influence contemporary cognitive neuroscience and artificial intelligence

Conclusion

The development of information processing theories marked a crucial transition in psychology from behaviorist to cognitive approaches. By providing mathematical frameworks for understanding mental processes, researchers like Donders, Shannon, Hick, and Hyman established the foundation for modern cognitive psychology. Their work demonstrated that mental processes could be studied scientifically and quantitatively, paving the way for the cognitive revolution that would transform psychology in the latter half of the 20th century.

The information processing approach continues to influence contemporary research in cognitive psychology, neuroscience, and artificial intelligence, demonstrating the enduring value of understanding the mind as an information processing system.

References

• Neisser, U. (1967). Cognitive Psychology. Appleton-Century-Crofts.