selective breeding for maze kearnung

Selective Breeding in Psychology

Introduction to Selective Breeding

Selective breeding, particularly in psychology, examines the influence of genetic variation on behavior. This area of research was significantly advanced by Robert Tryon in the 1920s. His groundbreaking work aimed to demonstrate that particular behaviors are heavily influenced by genetic factors.

Robert Tryon's Research (1942)

In 1942, Robert Tryon initiated the first long-term, systematic study focused on selective breeding for behavioral traits:

Objective of the Study

  • Tryon sought to establish whether the ability to engage in specific behaviors, such as learning and problem-solving, could be shaped by genetic differences.

Methodology

  1. Initial Testing of Rats: Tryon began his study by assessing a genetically diverse group of rats based on their ability to navigate a maze. The measurement of success was determined by the number of errors made while solving the maze.

  2. Breeding Strains:

    • The rats that performed the best (making the fewest errors) were selectively bred to create the "maze bright" strain.

    • Conversely, the rats that made the most errors were bred to produce the "maze dull" strain.

  3. Generational Testing:

    • Once the offspring from successive generations reached adulthood, they were retested in the same maze. Best-performing individuals from the maze bright strain were mated, as were the worst-performing individuals from the maze dull strain. This selective breeding continued over multiple generations.

Results and Observations

  • Distinct Strains Development: Over generations, the traits of the two strains began to diverge significantly. By the seventh generation, there was minimal overlap between the behavioral performances of the two strains. Nearly all rats in the seventh-generation bright strain exhibited superior maze-solving abilities compared to even the best of the dull strain.

  • Cross-Fostering Experiment: To control against the possibility that behavior was being learned from the mothers, Tryon implemented cross-fostering. Some individuals from the bright strain were raised by dull strain mothers and vice versa. The findings showed:

    • Rats from the bright strain maintained their maze-solving proficiency, regardless of their foster mothers.

    • Rats from the dull strain consistently displayed poor maze-solving abilities, irrespective of nurturing circumstances.

Implications for Behavioral Genetics

After establishing distinct behavioral strains, further questions arose regarding the correlation between selected traits and other behavioral or physiological attributes. Although labeled "bright" and "dull," Tryon's study primarily measured performance in maze navigation; hence:

  • It is acknowledged that successful maze performance depends on a range of sensory, motor, motivational, and cognitive processes. Hence, any change in these underlying processes could likely mediate the observed behavioral effects.

Summary of Findings

Tryon's work laid foundational insights into the heritability of behavior. The observed divergence in the maze performance of the two strains led to an enhanced understanding of how genetics can influence not only specific behaviors but also the potential for behavioral traits to cluster with other physiological characteristics. This research marks a crucial step in understanding the interplay between genetics and behavior.