Imre Lakatos ( ) The rationality of science Zoltán Dienes, Philosophy of Psychology

Popper’s falsificationism (as construed by Lakatos) Popper was a fallibilist: we might be wrong about any piece of knowledge. Theories must be made to stick their neck out. But we can only criticise one thing (e.g. a theory), if we take for true other things. To be critical about anything, we must decide to accept other things.

Methodological falsificationism Popper was a fallibilist: we might be wrong about any piece of knowledge. Theories must be made to stick their neck out. But we can only criticise one thing (e.g. a theory), if we take for true other things. To be critical about anything, we must decide to accept other things. Decision 1 Decide what can be legitimate independent and dependent variables Scores on a certain extroversion scale Reaction times

Decision 2 Decide which measurements you will accept you will accept. Take a measurement. But do you trust that reading/score? Safety control: repeat the measurement/experiment (matter of convention how many times) In taking these measurements fallible theories are involved; but for the sake of testing another theory we take them as unproblematic background knowledge.

How can we reject probabilistic theories? Decision 3: Accept a certain level of significance e.g. p <.05

Decision 4: Check assumptions of tests, data well behaved, background knowledge safe. Decide to accept all is in order so can be guided by the test outcome. Then results against a theory falsify it. We must reject the theory and not work on it again on pain of being irrational.

According to Lakatos, this Popperian account differs from the history of science in several ways. Lakatos: Historically all theories have been ‘born falsified’ into an ‘ocean of anomalies’. Scientists can rationally work on a theory already ‘falsified’ and also change their mind about the conditions that would falsify a theory. A scientific theory can become a hard core of a research programme, treated (for some time) as immune to falsifications.

The methodology of scientific research programmes A research programme has a hard core, a protective belt, and a positive heuristic. Hard core: the central beliefs of the programme – e.g. In connectionism: psychological states consist of activation flowing between units through adjustable weights We are forbidden from falsifying the hard core

Protective belt: Specific theories based on the hard core. Must invent auxiliary hypotheses that form a protective belt around the core, and direct falsifying conclusions to them – they get adjusted, re-adjusted or replaced to defend the thus hardened core. For example, a specific connectionist network of children learning to read A specific network of the perception of faces If evidence goes against any of these theories, these specific networks are falsified, not connectionism generally

Positive heuristic: Guidelines on how to deal with falsifying evidence by modifying the refutable protective belt. For example, if a network does not make the right predictions, consider changing: The learning rule The pattern of connectivity What the input and out put units code

The basic unit of evaluation is the whole research programme. If an adjustment predicts some hitherto unexpected fact the change is theoretically progressive; if some of these predictions are corroborated, it is empirically progressive. Otherwise the problem-shift is degenerating. Ad hoc 1 : The change does not predict anything new. Ad hoc 2 : The change does make new predictions but they are not corroborated. Ad hoc 3 : The change was not based on the positive heuristic.

Thinking in terms of progressive or degenerating problem shifts rather than Popper’s falsification: Less arbitrary. Any of our decisions can be appealed. We don’t have to stick with any of them. The decisions can be overturned if that leads to a progressive problem-shift.

It is rational to work in a research programme that is already “refuted” – anomalies can be pushed aside with the hope they will turn into corroborations in the fullness of time. The positive heuristic drives us forward. Research programmes have achieved monopoly only rarely; the history of science is and should be the history of competing research programmes. The sooner competition starts the better.

Contrary to (early) Popper: scientists can frequently and rationally claim that experimental results must not be reliable, or that the discrepancy with theory is only apparent and will disappear with the advance of theory. But, like Popper: we must retain the determination to eliminate, under certain objectively specifiable conditions, certain research programmes.

Contrary to (early) Popper: scientists can frequently and rationally claim that experimental results must not be reliable, or that the discrepancy with theory is only apparent and will disappear with the advance of theory. But, like Popper: we must retain the determination to eliminate, under certain objectively specifiable conditions, certain research programmes. A research programme is given up if it is degenerating while another is progressive. It is only when a progressive programme explains the failures of a degenerating one that the degenerating one is treated as falsified.

The mind evolved by natural selection; Most fundamental human characteristics evolved in the Pleistocene Hard core Evolutionary psychology Protective belt Parental investment theory and mate selectivity Cheater detection module Human sperm competition Attractiveness of symmetry Timing of sex with lovers and long term partners Positive heuristic Positive heuristic: Think more carefully how Pleistocene conditions map onto modern day life; could the apparent adaptation really be a consequence of another adaptation; was the experiment ecologically valid

All learning is conscious Hard core One approach to learning Protective belt When learning complex grammars, people learn small chunks of words Conditioning results from conscious hypothesis testing People often base decisions on memorized exemplars Positive heuristic Positive heuristic: Is something else simple people may have learned? How could the test of conscious knowledge be made more sensitive?

Note on novelty: Progressive means making novel predictions that are confirmed. But what exactly counts as a novel prediction and why is novelty important? Early Lakatos: A novel prediction must be predicting a finding never discovered before (“temporal novelty”). Late Lakatos: A prediction is novel for a theory if it was not used in constructing the theory (”use novelty”). A prediction can be novel even if it occurs in the same paper as the theory (contrast Donovan, Laudan & Laudan, 1992). Contrast Bayesian theory