A supporter of Neoclassical theory in her early days (being a student of Pigou), she refined the theory with her contributions to the area of imperfect competition. She explored the multi-dimensional nature of competition providing a breakdown from the existing traditional (Marshallian) world of perfect competition. The Chamberlin-Robinson model of monopolistic competition brought into focus the complexities of market forms in the real world as opposed to the ideal. Her fundamental insights on industry (in terms of production decisions for a multi-commodity firm), limits to competition, price policy for an entrepreneur, and monopoly/monopsony, furthered the scholarly discourse on imperfect markets.
The Keynesian revolution marked her active indulgence in the Keynesian theory of output and employment in the 1930s. She enriched the Keynesian tradition by attempting to apply the Keynesian concepts of involuntary unemployment and the paradox of thrift to a long run analysis.
An intellectual interest in Marxism (being inspired by Kalecki and by engaging in constant debates with Kaldor and Kahn) led her to believe that applying Marx's schemas of reproduction was the most logical approach to decipher the issues within and beyond The General Theory. Her model was an amalgamation of Keynesian, Kaleckian, Marxian and Classical ideas. She also attempted to bridge the 'Equilibrium method' and the 'Historical method' that existed in the Classical and Marxian analysis.
During the 1960's along with Piero Sraffa, she participated in the Neo-Ricardian “Classical Revival” against the Neoclassicals- also known as the 'Cambridge Capital Controversy'. Her critique of the Marshallian approach was on methodological grounds thereby attacking the 'Marginalist' approach of the Neoclassicals. She targeted the marginal productivity theory by attacking John Bates Clark's claim that wages and profit rates were determined by the relative scarcities of labour and capital. She argued in favour of capital being a heterogenous entity thereby contesting that various issues pertaining to the determination of prices of various capital goods had not been accounted for by the Neoclassicals. Moreover, she claimed that although firms in the competitive market were price takers, prices were determined within the entire economic system and hence could not be considered as a given for calculating the wages and profit rates (an idea also evident in Sraffa's work 'The Production of Commodities by Means of Commodities'). She went on to successfully debunk the concept of capital being a scarce input to production, thereby providing an insurmountable critique of the aggregate production function in Neoclassical theory.
Joan Robinson was also highly critical of the notion that a scientific approach to economic theory could be attained by incorporating mathematics into the discipline. She believed that such an approach would generate vagueness in the discipline as mathematical operations were performed on entities that are difficult to be defined (Robinson in Classical and Neoclassical theories of General Equilibrium, Walsh and Gram, 1980).
Her approach towards the discipline was to look 'behind the formal structures of theories to see what sorts of society- their history, “rules of the game,” sociological make-ups -were implied' (Harcourt.G.C, Joan Robinson and her circle).
In the later years of her life, she felt a growing discontent for the manner in which economic theory had progressed. Her frequent travels to India (wherein she engaged in a long standing academic relationship with Amit Bhadhuri), China and other LDCs convinced her that the prevailing economic theory was incapable of addressing the problems of unemployment, poverty etc. As several economists have contested, it is still too early to figure out what place among the economists of the 20th century will the history of economic ideas assign to such a remarkable woman as Joan Robinson (The Economics of Joan Robinson by Marcuzzo, Pasinetti and Roncaglia, 1996). Unfortunately her magnanimous contribution towards economic theory, which was widely expected to deliver the first Nobel Prize in economics to her, failed to do so, reflecting the strong ideological biases in the discipline.