Figure 1.
Graphical outline of the Drift Diffusion Model (DDM).
The two sample paths represent accumulation of evidence from a presented female face stimulus; resulting in either a correct (black line) or incorrect response (grey line). As shown in the RT histograms, responses more often accumulate towards a correct choice (above) than an incorrect choice (below). Drift rate () represents the average amount of evidence accumulated per time unit. Boundary separation (
) represents how much evidence is needed before a definitive response is made.
Figure 2.
Example of a face with all spatial frequency information (allSF), only low spatial frequency information (LSF), or only high spatial frequency information (HSF).
Note that the prints underestimate the contrasts used in the current experiment, especially for the LSF and HSF pictures.
Figure 3.
Visual stop-task. Each trial started with a white fixation-cross followed by a male or female face stimulus, indicating a left or right response.
During stop trials, a tone was played at some delay (SSD) and instructed participants to suppress the indicated response. The presented face stimulus contained allSF, only LSF, or only HSF information. Prints underestimate the contrasts used in the current experiment, especially for the LSF and HSF pictures. The letters displayed on each face are only included here for clarity and were not on top of the faces during the experiment.
Figure 4.
Experiment 1: Effects of spatial frequency information during the visual stop task.
A) Both Go RT (left panel) and choice errors (middle panel) increased when spatial frequency information was degraded. There right panel shows how the efficiency to withdraw a response (SSRT) improves, when categorization is more difficult. B) HDDM individual subject parameter estimates. When spatial frequency information was removed, the rate of information accumulation, “drift rate” (
) decreased (left panel), whereas the decision “boundary” (
) to categorize the face stimuli on time was lowered (middle panel). The right panel illustrates how lower drift rates, and decision boundaries together can result in prolonged RT and more errors.
Table 1.
Behavioral overview of all visual stop task experiments.
Table 2.
Estimated HDDM parameters for all visual stop-task experiments
Figure 5.
Prior to each trial a cue was presented indicating a speeded (“SP”) or accurate (“AC”). The presented face stimulus (male or female) indicated a right- or left- response, and contained allSF, only LSF, or only HSF information. After a speed cue, trials were followed by feedback stating “on time” if responses were below 450 ms, and “too late” if responses were larger than 450 ms. Accuracy trials were followed by feedback stating either “correct” if participants responded correct or “incorrect” when an error was made. For simplicity, the cue and feedback text are displayed here in English, in the real experiment these were provided in Dutch. Prints underestimate contrasts used in the actual experiment, especially for the LSF and HSF pictures. The letters displayed on each face are only included here for clarity and were not on top of the faces during the experiment.
Figure 6.
Experiment 2: visual stop task, with or without prior information about spatial frequency type (cue).
A) In both experiments Go RT (left panel) and choice errors (middle panel) increased when spatial frequency information was removed. Again, response inhibition was more efficient when categorization became more difficult (right panel). Prior knowledge about frequency type improved only response initiation (Go RT). B) Parameter estimates obtained from HDDM showed a decrease in “drift rate” (
) (left panel) and decision “boundaries” (
) (right panel) with the removal of spatial frequency information.
Figure 7.
Effects of spatial frequency on decision-making.
A) The difference between speeded- and accurate- reaction times (SAT) increased over the three frequency conditions. B) Overall, error rates increased over the three conditions while the SAT in choice errors became smaller between fast and accurate trials. Computational modeling indicated that the speed of information accumulation is decreased over the three conditions (C). The amount of information required to produce a response is higher when instructed to respond accurately, but decreases across the frequency conditions for both speeded and accurate instruction trials (D).
Table 3.
Behavioral overview speed-accuracy experiments.
Table 4.
Estimated HDDM parameters during decision-making.