Psychology has claimed to be the science of mental life (James, 1890) and human behaviour (Watson, 1924) and yet its place as a science has yet to be fully established. Referring to historical approaches, philosophical argument and contemporary challenges, this essay will consider the position of psychology as a scientific discipline, discussing its paradigm shifts and relationship with the scientific method. Definitions of both science and psychology will be explored to demonstrate that psychology’s reach is within and beyond the boundaries of science.
Psychology as a natural science dates back to Aristotle (Hemmings, 2018) but its zenith as a philosophical psychology came with Descartes (Collin et al., 2015), before Locke and Hume revisited Aristotle’s belief in knowledge through sensory experience and perception (Hume, 1955; Locke, 1975). This empiricism appealed to Bacon (Rossi, 1968) who argued for a systematic approach to understanding. Following the path of physics, psychology adopted logical empiricism as a route towards science, requiring a departure from philosophy. This came in 1879 with the first psychology laboratory, where Wundt applied experimental methods and introspection to mental phenomena (Gross, 1997). However, psychology was not the branch of physics that Carnap (1932) envisioned.
An inability to explain mental processes through objective means, led logical positivists to a demarcation of science, reconciling logic with empiricism (Hull, 1943; Quine, 1951). A scientific method, as expressed by the Vienna Circle (Sarkar, 1996), was then proposed, with testable predictions, systematic observation and verification. However, evidence supporting a theory failed to render it scientific, forcing the positivists into accepting that theories may contain unobservable variables. With the Vienna Circle unable to define science, falsification offered a new criterion (Popper, 1934), encompassing ahistorical and universal theories. Popper’s (1934) view was that, with truth unprovable, science’s concern should be the disproval of hypotheses. Psychologists adopted Popper’s scientific process (Popper, 1959) but it was restrictive. As Lakatos (1970) argued, scientists should not always abandon theories that lead to falsified prediction. Quine (1974) offered support, adding that a theory offers multiple claims and should not be rejected for one falsified statement. As Sagan (1996) later argued, understanding is more important than a pretention to certitude. Psychology risked being classified as folk science, based on common sense and consensus, unless it adopted the scientific method.
Kuhn argued that psychology was preparadigmatic (Kuhn, 1962) as various models competed for acceptance. Accused of being a relativist, Kuhn responded that science always leads to progress, and that psychology could not be a science until it had a general theory of consensus (Thomas, 1962). Other psychologists, such as Palermo (1971), believe that psychology was a science because it had been through what Kuhn termed paradigm shifts (Kuhn, 1962). Alternatively, it could be argued that psychology’s paradigms have coevolved. Either way, it is problematic for psychology’s scientific merits that it has no consensus of definition as it moves with advancements and changes in culture and language. Its illusiveness results from humans studying humans, reflexivity that exposes psychology to the reality that psychologists attempt to explain their own behaviour.
Psychology’s lack of consensus, and division into sub-disciplines, lend credence to Kuhn’s view of the discipline as a pre-science. However, Kuhn’s importance of unanimity (Kuhn, 1962) fails to acknowledge how psychology’s combination of approaches provides a more complete, arguably scientific, picture. O’Connor et al. (2020), for example, outlined how experts from different sub-fields of psychology - including biological, cognitive, clinical and educational – worked together to decide how to prioritise their research during the Covid-19 pandemic. Its varied approaches to research offer a range of methodologies, adopted to suit chosen hypotheses, with a mixed use of methods, triangulation or methodological pluralism, offering a deeper comprehension and, befitting of a constructivist approach, allowing for different realities. Furthermore, from his analysis of journals, Boyack et al. (2005) demonstrates that science and psychology widely cite each other’s papers, a relationship that has since been strengthened by psychology’s reaction to the replication crisis.
Questionable research practices, such as low statistical power (Cohen, 2013), HARKing (Kerr, 1998), p-hacking (Raj et al., 2018) and failure to control for biases (Norris & O’Connor, 2019) forced psychology into undergoing a scientific renaissance (O’Connor, 2021) argued for by Munafò et al.’s, (2017) manifesto that called for the use of scientific process: of methods, reporting and dissemination, reproducibility, and evaluation. Subsequent improvements in research standards have changed how psychology is conducted (Chambers & Tzavella, 2022). The extended use of ‘in principle acceptance’ (Norris & O’Connor, 2019), acknowledging that disproven theories drive progress, will further advance psychology’s standing as a science.
In conclusion, psychology coexists inside and outside the laboratories that once represented its scientific ambition. In striving for an understanding of the fullness of experience, different approaches have arisen under the banner of psychology, with some approaches overlapping with science more naturally than others. Understanding is about the ‘how’ and the ‘why’ (Leahey, 2004) and humans are too complex, too individual, to be reduced to lower-level explanation. Psychology’s focus may keep science at a distance but, as science wrestles with its own definition, it may be that science embraces psychology.
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