How did behaviorism challenge William McDougall’s theory of instinct?

Behaviourism challenged William McDougall’s theory of instinct by rejecting his reliance on subjective, purposive explanations, which behaviourists argued were beyond scientific observation and validation.1

McDougall’s theory posited that instincts were driven by innate, subjectively experienced urges aimed at specific goals. In contrast, behaviourists—led by figures such as John B. Watson—insisted that psychology should be an objective science focused strictly on observable relations between environmental events and behaviour.12

Key points of the challenge included:

• Rejection of Subjectivity: Behaviourists criticized McDougall for appealing to "subjective purposiveness," which they deemed vague conjecture rather than hard fact.1
• Emphasis on Experience: Critics argued against the assumption of an innate basis for complex behaviour, asserting instead that most actions are moulded by experience and conditioning.12
• Scientific Rigor: The 1919 "anti-instinct revolt," initiated by Knight Dunlap, formally attacked the validity of instinct as a scientific concept, demanding that psychological explanations be grounded in experimental evidence.1

Ultimately, behaviourists sought to replace the concept of instinct with observable reflexes and learned responses, effectively sidelining McDougall’s purposive psychology by the 1930s.12