Context-Dependent Mechanisms in Numerosity-Time Interactions

Candice T. Stanfield-Wiswell

Advisor: Martin Wiener, PhD, Department of Psychology

Committee Members: Craig McDonald, Matthew Peterson

Online Location,
April 28, 2023, 11:00 AM to 01:00 PM


Humans use magnitude information from the environment, like numerical quantity and time intervals, to make predictions and plan actions. Evidence shows magnitude dimensions interact and bias each other congruently: larger numerical quantities are perceived as lasting longer in duration than smaller quantities. However, because those studies required subjects to discriminate between stimuli, it is unclear if the congruency effect is due to decisional bias. To determine whether this phenomenon is dependent upon making comparisons, we investigated contextual changes in numerosity-time tasks across four experiments. First, a non-comparison bisection task was employed to reduce decisional bias. Subjects judged whether a dot quantity was small or large (seven log-spaced quantities 10–90) or whether a duration was short or long (seven log-spaced intervals 750–2250ms). An incongruent effect was observed, with larger numerosities perceived as quicker in duration than smaller numerosities, contrary to previously reported findings. Other factors known to interfere with processing were tested: neither eye fixations nor memory affected judgments. Next, we verified the congruency effect using a discrimination task with the same stimuli, confirming the decisional bias hypothesis. To further test the hypothesis and eliminate decisional bias, subjects performed a time reproduction task using a continuous keypress paradigm. A version of the congruency effect emerged: durations were significantly over-reproduced and under-reproduced as numerosities increased and decreased, respectively. Overall, our findings indicate that contextual changes in task design induce response bias, modulating the effect direction.