The effects of incidentally learned temporal and spatial predictability on response times and visual fixations during target detection and discrimination

Abstract

Responses are quicker to predictable stimuli than if the time and place of appearance is uncertain. Studies that manipulate target predictability often involve overt cues to speed up response times. However, less is known about whether individuals will exhibit faster response times when target predictability is embedded within the inter-trial relationships. The current research examined the combined effects of spatial and temporal target predictability on reaction time (RT) and allocation of overt attention in a sustained attention task. Participants responded as quickly as possible to stimuli while their RT and eye movements were measured. Target temporal and spatial predictability were manipulated by altering the number of: 1) different time intervals between a response and the next target; and 2) possible spatial locations of the target. The effects of target predictability on target detection (Experiment 1) and target discrimination (Experiment 2) were tested. For both experiments, shorter RTs as target predictability increased across both space and time were found. In addition, the influences of spatial and temporal target predictability on RT and the overt allocation of attention were task dependent; suggesting that effective orienting of attention relies on both spatial and temporal predictability. These results indicate that stimulus predictability can be increased without overt cues and detected purely through inter-trial relationships over the course of repeated stimulus presentations.

Figure 1. Reaction times from Experiment 1 for each level of temporal and spatial predictability.

Error bars represent standard error of the mean.

Figure 2. Average RT for each ISI at each level of temporal predictability in Experiment 1.

RTs are averaged across the levels of spatial predictability within each level of temporal predictability. Error bars represent standard error of the mean.

Figure 3. The percentage of trials when the target location was fixated prior to target onset, fixated after target onset, and not fixated at all for all levels of temporal and spatial predictability.

Figure 4. Reaction times from Experiment 2 for each level of temporal and spatial predictability.

Error bars represent standard error of the mean.

Figure 5. Average RT for each ISI at each level of temporal predictability in Experiment 2.

RTs are averaged across the levels of spatial predictability within each level of temporal predictability. Error bars represent standard error of the mean.

Figure 6. The percentage of trials when the target location was fixated prior to target onset, fixated after target onset, and not fixated at all for all levels of temporal and spatial predictability.