There are two different tasks possible in this experiment: magnitude estimation and ratio estimation. In the tasks using the linear or logarithmic slider, the observer is presented with a single display of dots and must move a slider along a scale to correspond to the estimated number (magnitude) of dots seen in the display. In the tasks that require ratio estimation, the observer is presented with two displays and must enter the (perceived) ratio of the number of dots seen in the second display divided by the number of dots seen in the first display.
The flexibility of the program allows the experimenter to explore factors such as the range of possible stimuli, the dot regularity, the type of task, the nature of the response-display interaction, and the type of trial-by-trial feedback. First, select the number of blocks and trials per block that you wish to run and then set the values of the block parameters (maximum display size, dot regularity, standard, response type, scroll information, and trial feedback) for each block. You may want to randomize the order of conditions over blocks. STEP to each block number and SET the desired block parameters. After SET-ting the task for each block, it's a good idea to review all the block conditions by stepping through them with the STEP button.
| Max Size | The maximum number of dots possible in the display. It may be set to 100, 200, or 400. |
| Dot Regularity | This is either Low or High. A Low setting corresponds to a minimum dot-to-dot distance of 5 display pixels. A High setting corresponds to a minimum dot-to-dot distance of 10. (See the Technical Details section for additional information on the constraints on the display that are imposed by the dot-to-dot distance, and the interaction of this parameter with Max Size on average dot density.) |
| Standard | This is the exact number of dots displayed in the standard display (only used in the ratio estimation task). It may be set anywhere from 1 to 400. |
| Response | The nature of the response: Lin for linear slider, Log for logarithmic slider, and Ratio Est. for the ratio estimation task. |
| Scroll Info | This specifies the nature of the display associated with the slider (or scroll bar) response mode. Labels means that number labels appear on top of the slider to facilitate making a response of a specific estimate of dot number. |
| Feed Back | No means no feedback is provided after a trial. Yes means that full information about the stimulus and response are provided. |