Internal reference updating in visual duration discrimination: A search for boundary conditions

A growing body of psychophysical research suggests that the discrimination of successive stimuli involves more than taking the difference between their sensation magnitudes, challenging traditional difference models. Two elaborated theories assume that each sensation magnitude is weighted by its reference level (sensation weighting model) or that the second sensation magnitude is compared to a dynamically updated internal reference, in which the first sensation magnitude gravitates towards the previous reference level (internal reference model). Whereas both models can explain higher discrimination sensitivity when the standard precedes the comparison (negative Type B effect), only the sensation weighting model can account for higher discrimination sensitivity when the standard follows the comparison (positive Type B effect). Most previous studies reported negative Type B effects, while some positive Type B effects have also been reported, especially for duration discrimination with short stimulus durations and/or short inter-stimulus intervals combined with adaptive-staircase procedures. The present study systematically searched for positive Type B effects in visual duration discrimination by orthogonally varying stimulus duration (80 vs. 500 ms standard), inter-stimulus interval (200 vs. 900 ms), and stimulus type (filled vs. empty intervals) across four experiments using the method of constant stimuli. Type B effects were consistently negative across all experimental conditions and analysis methods. The absence of positive Type B effects is consistent with the internal reference model and casts doubt on whether the additional flexibility in the sensation weighting model is needed to explain visual duration discrimination sensitivity.