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| Partial Report
Partial report is an experimental methodology developed by George Sperling (1960) in the late 1950's. At that time there was a cognitive concept called the span of apprahension, bet you did not read about it in your textbook, that said human's are able to recall between 4-6 items in a single glance, if you will. This limit represented the limit of information we can take in instantly. This conclusion was drawn using a methodlogy Sperling termed whole report. In whole report you present a string of letters or numbers and ask the participant to recall all of them that they can.
Partial report takes a different attack. Instead of a string, an array of letters (3 x 3 or 4 x 4 are common) and after the letters are presented, a signal is given to indicate which row the person is to recall. So the participant is asked to recall only some of the items but they cannot know which items before hand. Thus, Sperling called this partial report. By multiplyig the percent correct by the total number of items, he determined the total items the person had when the arrow was shown (this is why the person cannot know which row will be indicated until after the letters are removed). He found rates from 8 (for 3 x 3 arrays) to 10 (for 4 x 4) letters available (Sperling, 1960) when the arrow immediately followed the array. These numbers are much greater than the span of apprahension concept allowed, and, thus, your not reading about it in class. As the delay was increased, the number of letters available declined to the range of the span of apprahension by about 500 ms.
These findings led to an important changes in how we understand how we take in information. One of the changes was the proposal that in addition to short-term and long-term memory, we have short-term sensory stores that last for very brief periods of time. Neisser (1967) termed the one for the visual system, that Sperling studied, iconic memory.
In this experment you can try out the partial report method. There are several parameters below you can alter to make your own unique
References:
Neisser, U. (1967). Cognitive psychology. New York: Appleton-Century-Crofts.
Sperling, G. (1960). The information available in brief visual presentations. Psychological
Monographs: General and Applied, 74(11, Whole No. 498). 1-29.
You can adjust several parameters to design your own version of the experments. The settings are discussed below.
You can adjust several parameters to design your own version of the experments. The settings are discuss below.
Number of Rows: Number of rows in the letter array to present.
Number of Columns: The number of items in each row of the letter array.
Report What?: you can ask the participant to report either rows or coumns
of the letter array.
Duration of Stimulus (ms): how long the stimulus is presented. Sperling (1960)
used 50 ms but that his hard for most monitors to reproduce well. He used a tachistoscope.
Font Size: choose the font size of the letters. The bigger the letters
the farther the outside letters will be from the fovea.
Background Gray Level : the brightness of the background, in basic display units.
This variable alters the contrast between the letters and the background.
Duration of Fixation (ms): how long the fixation mark is on (ms).
Stimulus Delay (ms from end of fixation): how long after the fixation mark is removed
till the beginning of the stimulus. This number needs to be big enough for any arrows that occur before
the stimulus (the negative numbrer includes the duration of the stimulus).
Reset Stimulus At the top of the settings is a Reset Stimulus button.
Pressing this button restores the method settings to their default values.
Select the delays between the end of the letters and the presentation of the arrow you w
ish to use. (0 is presented just as the array is removed and - values are presented before
the array is removed): this is the principle independent variable during the
experiment. This is the different levels of delay from the end of the stimlus to the beginning of
the arrow. As stated above, negative numbers will occur before the stimluls is removed.
Number of Trials/Delay: how many trials at each level of delay.
Reset Method At the top of the settings page is a Reset Method button.
Pressing this button restores the stimulus settings to their default values.
Change the settings below to alter the stimulus parameters in this experiment.
Change the settings below to alter the parameters of the experimental method.
Below, press the spacebar or the Open Experiment Window button on the screen to open the window where the experiment will run. When this screen opens, press the spacebar or click the "Start" button to begin the experiment. There are instructions above the "Start" button. Read them to know how to perform the experiment. Keep your eyes fixated on the red plus sign in the middle of the screen. Press the space bar to go to the next trial.
Your data will be presented on the results tab. The x-axis will have the delays. The y-axis will show the percent correct for each delay. To download your trial-by-trial, press the Show Data link. To download the summary data press the Show Summary link. This data will be stored in a csv format readable by most spreadsheet and statistical programs.