The behavioural approach emerged in political science in the mid-20th century, aiming to make the study of politics more scientific and empirical. Its importance lay in shifting the focus from normative questions (what ought to be) to observable political behaviour (what is). Key aspects of its importance include:

• Scientific Rigor: Behaviouralism sought to apply methods from natural sciences, emphasizing systematic observation, data collection, quantification, and hypothesis testing. This led to the development of more sophisticated research techniques and statistical analysis in political science.
• Empirical Focus: It moved away from historical and philosophical speculation towards the study of actual political actors and their actions, such as voting patterns, political participation, elite decision-making, and public opinion.
• Theory Building: By focusing on regularities and patterns in political behaviour, behaviouralists aimed to develop generalizable theories and even predictive models of political phenomena.
• Interdisciplinary Influence: It encouraged the integration of insights and methods from psychology, sociology, and economics, broadening the scope of political inquiry.
• Objectivity: Proponents believed that by focusing on observable behaviour, political science could achieve greater objectivity and value-neutrality, separating facts from values.

However, the behavioural approach began to decline by the late 1960s, giving rise to the 'post-behavioural revolution,' due to several criticisms and limitations:

• Neglect of Normative Questions: Critics argued that by focusing solely on observable behaviour and quantifiable data, behaviouralism ignored crucial normative questions of justice, ethics, and the 'good society,' rendering political science less relevant to real-world problems.
• Irrelevance to Pressing Issues: The approach was perceived as being too abstract and detached from the urgent social and political crises of the time, such as the Vietnam War, civil rights movements, and poverty. Scholars felt it failed to offer solutions or even meaningful analysis of these critical issues.
• Methodological Limitations: The attempt to quantify all political phenomena often led to oversimplification or the neglect of complex, qualitative aspects of politics. Critics questioned the feasibility of achieving true value-neutrality and the difficulty of measuring subjective political attitudes and beliefs accurately.
• Overemphasis on Micro-level Analysis: While useful for studying individual behaviour, it sometimes overlooked the broader structural, institutional, and historical contexts that shape politics.
• Lack of Predictive Power: Despite its scientific aspirations, behaviouralism often struggled to provide accurate predictions for major political events, undermining its claim to scientific rigor.

The decline of behaviouralism did not mean its complete abandonment, but rather a re-evaluation and integration of its empirical strengths with a renewed interest in normative theory, institutional analysis, and a more holistic understanding of political life.