[visionlist] Forced Choice – please educate me

[Michael Bach]

Dear Colleagues:

I have the impression that the general understanding of a psychophysical forced-choice paradigm has changed over the decades.

To my understanding, bias/criterion effects can only be effectively mitigated in an nAFC (n-alternative forced choice) design where the alternatives are _equivalent_. Examples: the pattern is on the right/left (balanced, of course), the stimulus was in the first/second interval, or the gap of a Landolt C is in one of 8 directions. “Equivalence” may be challenging to achieve, particularly in the latter case, where the oblique effect may interfere.  Alternatives such as “seen/not seen” or “go/no” are not equivalent and necessitate measures (d’, …) to address bias/criterion.

For me, nAFC implicitly implied equivalent alternatives, but was this ever the case? Whatever, young scientists do not seem to understand it this way.

While this might be just seen as a nomenclature trifle, the real problem arises due to the prevalent “scientific folklore” that a forced-choice paradigm eliminates the effects of bias / criterion change (which, in particular, occur through perceptual learning in longitudinal studies). However, if forced-choice does not employ _equivalent_ alternatives, this assertion is invalid.

I have encountered opinions suggesting that the addition of a “not seen” button constitutes forced choice (yes…, but:) and also eliminates bias…


Looking forward to your advice, best, Michael
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https://michaelbach.de