A low-level explanation of paradoxical motion percepts
Bibliographic record
Abstract
A recent series of experiments have demonstrated a deterioration of motion perception with increasing stimulus size for stimuli of high contrast (Tadin et al., 2003). This counterintuitive finding has been explained as a result of surround-suppression in visual area V5. Equally paradoxical was the finding that older observers appeared to show better motion perception than younger observers using the same technique (Betts et al., 2005). This second curious result was explained as a consequence of a reduction in V5 surround-suppression due to age-related changes in GABA-mediated inhibition. Using an opponent-motion stimulus, similar to that of previous studies but of constant duration, we have replicated the paradoxical effect of contrast on motion discrimination and also replicated the finding that this effect is much reduced or non-existent in older subjects. Our results can, however, be explained by low-level mechanisms: a proportional increase in the motion energy required to discriminate stimuli of progressively higher suprathreshold contrasts and spatial summation of motion in stimuli of progressively larger sizes. In previous studies, suprathreshold contrast co-varies with size, which may be responsible for the unusual results. TadinD.LappinJ. S.GilroyL. A.BlakeR. (2003). Perceptual consequences of centre-surround antagonism in visual motion processing. Nature, 424(6946), 312–315. Betts L. R. TaylorC. P.SekulerA. B.BennettP. J. (2005). Aging reduces center-surround antagonism in visual motion processing. Neuron, 45(3), 361–366.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".