Chapter 1. Partial Report

1.1 Introduction

How much information can a person gather from the world at one glance? In this experiment you will be shown a cluster of letters, for example three rows of three letters each. After the letters are removed, you will be shown an arrow that will indicate which row you are to recall. The initial array of letters will only be shown for a very short period of time, so trying to remember the letters by actively reading them will not work because you do not have enough time thus, you should try to hold the whole array of letters in memory as best you can.

1.2 Experiment Setup

1.3 Instructions

You will need to press the space bar to begin the experiment. At the beginning of each trial, a fixation mark will appear. Please look at this mark. After it is removed, an array of letters will be presented in three or more rows. Look carefully at these letters, but do not try to read them. The letters will remain on screen only briefly. After they are removed, an arrow will appear pointing to the row you are to recall. Type the letters that you recall from that row and then press Enter to proceed to the next trial.

1.4 Experiment

1.5 Results

1.6 Debriefing

How much information can a person gather from the world from a single glance? That was the question George Sperling addressed in his 1960 study. At that time, people thought we could gather only a few items at any one moment. This belief was based on a technique called Whole Report, wherein subjects were shown a list of letters for a very brief period of time and asked to type all that they could recall. Generally, participants could recall 5 letters from the presented list. This limit was called the span of apprehension, a concept that is no longer used in cognitive psychology.

Sperling took a very different approach. He used what we now call Partial Report. Instead of being asked to recall the whole list, Sperling asked participants to recall/report only some of what they saw. An important part of this method was that the participant did not know what letters to recall until after the letters were removed. Let us make this concrete. He presented to his participants a 3 x 3 array of letters such as the one below:

X D F

Q P T

N W K

After the letters were removed, a tone would indicate which row was to be recalled. If the higher-pitched tone was sounded, the participant was to type XDF. In his initial study, he found that, in a delay of 0 ms, where the tone sounded immediately after the letters were removed, the participants correctly recalled more than 82% of the letters (Sperling, 1960). Since participants could not know which row to recall, Sperling could make an estimate that to be that correct, the participants needed to know about 9 (letters in the array)* 0.82 (the rate of correct recall) = 7.4 letters that had to still be retained by the participant. Two interesting observations: 1) the participants did not do better on trials when they were signaled the row to recall even before the presentation of the array of letters; 2) participants recalled better than the span of apprehension limit if the delay between the letters was less than half a second. It was clear that we retained more from a single glance than the Whole Report method shown. To some later researchers, these results indicate that we have a previously unnoted type of memory that holds visual information very briefly. They call this “iconic memory” (Neisser, 1967).

References:

Chow, S. L. (1991). Partial report: Iconic store or two buffers? Journal of General Psychology, 118(2), 147-169.

Neisser, U. (1967). Cognitive Psychology. New York, NY: Appleton-Century-Crofts.

Sperling, G. (1960). The information available in brief visual presentations. Psychology Monographs, 74, 1-29.

1.7 Quiz