Notes on Paul Meehl’s “Philosophical Psychology Session” #06

These are the notes I made whilst watching the video recording of Paul Meehl’s philosophy of science lectures. This is the sixth episode (a list of all the videos can he found here). Please note that these posts are not designed to replace or be used instead of the actual videos (I highly recommend you watch them). They are to be read alongside to help you understand what was said. I also do not include everything that he said (just the main/most complex points).

A core postulate is one that is found in every derivation chain or a postulate that consists of only core concepts. A core concept is one that is relied on implicitly in every derivation chain is in the hard core.

  • Statements are composed of concepts.
  • Lakatosian defence isn’t fraud if it’s done honestly and openly with a mind to test the new hypotheses.
  • General rule: justification for Lakatosian defence is that the theory has “money in the bank” due to previous corroborations. You also have to be clear when you are ad hoc defending your theory, being open and honest in general when defending your theory is crucial.
  • Objections apply mainly to soft areas of psychology (rather than hard) because soft relies on correlational whereas hard often uses experimental methods (with randomisation and manipulation).
  • 10 obfuscating facts in most soft psychology research that make it hard to interpret a narrative summary of research on a theory: not likely to be negligible size (rare we can write them off).
  • They individually vary from one study to another.
  • Usually not accurately judgeable in a study.
  • Frequently in opposition to each other: some make good theories look bad, whilst others make bad theories look good.
  • These together lead to “mental fog” when reading a review.
  • Meta-analyses are not good for testing theories.

10 obfuscating facts:

1) The fact the derivation chain is loose. In psychology it is almost unheard of that one writes down all of the postulates of the theory or all the auxiliaries. So much is assumed. When we use common sense to plug a gap in the chain the right half of the Lakatosian defence is no longer strictly deduced but is now probabilistic. This chain can only be deductive (according to Meehl) by being explicit with the assumptions and including the cp clause (but we don’t like to do this is psychology as it’s unlikely to be true). We often don’t write down a lot of the assumptions we make when doing an experiment (the list is longer for soft psychology than for behavioural genetics, which is in turn longer than the set of assumptions of a chemistry experiment). The more things left unsaid, the more of an obfuscator it is.

2) The auxiliary theories are explicitly stated but are problematic e.g. how a Rorschach test works, about psycholinguistics.

3) The cp clause is not only problematic but if taken literally is almost certainly false. Exceptionally unlikely that any value will not be correlated with e.g. sex, age, SES, geography, religion, etc. When stating cp we are not stating we’ve controlled all other factors, we’re saying all the other factors are either subject to randomisation or (for those we can’t randomise) we hope to god they are not too much correlated with an extraneous variable.

4) Imperfect realisation of the particulars (cn). The experimenter didn’t do quite what she said or they failed to mention something they did (so a reviewer later on wouldn’t know what was done and what was important). Experimenter bias (tone, whether the researcher believes in the theory or not) was shown to have a significant effect on Rosenthal’s research in the 1960’s. Experimenter bias effects has shown itself in all scientific disciplines, to the extent an instrument of measurement is not employed that’s highly objective in how you manipulate it, when a human being gets involved in the system as an input or an observer you have to worry about the experimenter bias. “Insane” publish or perish mindset is leading to greater fraud (Meehl states he has no opinion on this).

Correlations between people’s views and how they behave as referees changes between studies but there have been studies showing that this difference can have an impact on what is published in the biological sciences. Editors may not explicitly state they won’t publish anything on theory x because they think it’s wrong but they will choose the referees who (should) have an opinion on the field because they are knowledgeable about it. Editors will have own beliefs and rubrics which they bring to bear on a new paper. This can result in them judging it very early on and rejecting this. Must avoid this temptation as an editor.

This lack of clarity (with incomplete or incorrect descriptions of what was done) is the reason we are struggling with replication. Be careful with interpreting second replication; it isn’t always right.

5) Inadequate power (1-beta=power).

6) Lyken’s crud factor. In psychology, almost impossible to find a Pearson’s r correlation of 0.


Yonce, J. L., 2016. Philosophical Psychology Seminar (1989) Videos & Audio, [online] (Last updated 05/25/2016) Available at: [Accessed on: 06/06/2016]


    1. Thank you. It refers to the ceteris paribus clause (“all others equal”, or holding all other variables constant).

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