d′etectable: Fitting

You can select how many Trials to perform, the Duration of the stimulus on each trial, and the proportion of dots that exhibit Coherence when the signal is present. When you are ready, you can Run the task. At any time, you can temporarily Pause, or permanently Reset the task.

Each trial will begin with a fixation, +, then a stimulus, and finally a question mark, ?. Decide whether you think the signal is Present or Absent, and during the stimulus or question mark, respond by clicking Present to indicate a ‘Present’ response or Absent to indicate an ‘Absent’ response.

Based on the stimulus and your response (or lack there of), you will then receive feedback indicating whether this trial resulted in a Hit, Miss, False Alarm, Correct Rejection, or No Response.

The table of outcomes summarizes your Hits, Misses, False Alarms, and Correct Rejections, along with your Hit Rate, False Alarm Rate, and overall Accuracy.

In ROC space, your performance is plotted as Hit Rate versus False Alarm Rate. All of the points with the same Sensitivity (d′) are illustrated with an Iso-Sensitivity Curve. All of the points with the same Bias (c) are illustrated with an Iso-Bias Curve.

The visual representation of the SDT model shows your calculated Sensitivity as the distance, d′, between the distributions. And it shows your calculated Bias as the location, c, of the threshold. The threshold divides the Signal + Noise Distribution into regions of Hits and Misses and divides the Noise Distribution into regions of Correct Rejections and False Alarms.