The role of eye movements and induced motion on the strength of a trajectory illusion
Bibliographic record
Abstract
Purpose: When viewing transparently superimposed parallel and ‘expanding radial' dots, observers perceive the trajectory of some radial dots to be curved when, in fact, all trajectories are straight. The conclusion from prior experiments was that this illusion was a result of induced motion and pursuit eye movements. Observers also reported seeing the illusion when asked to track a horizontally moving (HM) dot in the absence of the parallel dots. The present experiments examine whether this finding is due to a minimal background being present or to a curved trajectory being traced on the retina. This investigation also examines how the strength of the illusion varies as a function of the direction of radial dot motion and the presence of a stationary central fixation (SCF) dot. Methods: The radial dot moved in 1 of 6 directions (clockwise: 0, 45, 135, 180, 225, or 315 degrees), had a straight or curved trajectory, and was embedded into a field of leftward parallel dots or presented alone. Observers fixated on the accelerating radial dot, on the constant-velocity HM dot, on the SCF dot, or were instructed to keep their eyes in the “center” while judging the trajectory of the radial or HM dot. Results: No illusion was reported in either the minimal background or the curved-trace conditions. Observers reported less of an illusion when the radial dot's direction of motion was against the movement of the parallel dots, and reported more of an illusion when asked to keep their eyes in the “center” versus when asked to fixate on a SCF. Conclusion: Results suggest that horizontal motion may be interpreted as a stable characteristic of the environment. The findings also provide support for the argument that induced motion plays a role in the trajectory illusion. However, the results question previous findings that the perceived shift in the focus of expansion (Duffy/Wurtz illusion) is not due to eye movements, but, rather, to an eye movement compensation mechanism.
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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 | 0.001 | 0.007 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
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".