Effect of intermixed foveal and parafoveal presentation on same-different judgments: Evidence for a criterion-inertia model

Abstract

Subjects judged whether two adjacent letters, which were presented either 0.5° (foveal or near condition) or 2.0° (parafoveal or far condition) from fixation, were identical or different. The preponderance of false-different responses (i.e., errors on same trials) over false-same ones increased, whereas the fast-same effect was eliminated, on the far pairs, but only when they were intermixed with near pairs rather than presented in separate (pure) blocks of trials. Intermixing the near and far pairs produced the opposite trends on near trials (i.e., smaller preponderance of false-different errors, larger fast-same effect). Carr et al., who presented trigrams, found a similar criterion misadjustment, which likewise depended on intermixed presentation. They proposed that their easy (familiar or orthographically regular) pairs produced a bias or criterion shift towards "same." No obvious biasing features were present in the near or far pairs, however, so the criterion misadjustment found here was attributed to the combined effect of internal noise and criterion inertia, not to criterion shifting. Increasing the level of internal noise on far trials produced more spurious perceived mismatches, but on mixed blocks of near and far trials, subjects relied on a common, compromise criterion for responding versus rechecking (recheck moderate perceived differences), instead of the separate, more appropriate criteria for near trials (recheck small differences) and far trials (recheck large differences) used on pure blocks. © 1985 Psychonomic Society, Inc.