The program MEMSCAN runs a version of the Sternberg memory scanning paradigm. On each trial, a set of to-be-
remembered digits is first presented. The size of the set varies on different trials from 1 to 6. The memory set is
then replaced by a plus-sign and, after a short delay, a probe digit. The subject's task is to respond as quickly as
possible by pushing the "/" key if the probe was a member of the set, or the "Z" key if the probe was not a member of
the memory set. If the response was incorrect, or if an invalid key was pressed, a short tone is presented. Raw data
from the experiment are placed in the file DSCAN.DAT. An analysis program (SCANANAL) reads the data file and
computes means and standard deviations of the reaction times for correct "present" and "absent" responses to each set
size. The output of the analysis is placed in the file ASCAN.ANL.
Running the experiment
To run the experiment type MEMSCAN and hit "Enter". When asked to "Press any key to begin", pressing the 'P' key will allow the user to change various parameters that determine the design of the experiment and the timing of trial events. Pressing a key other than 'P' will cause the program to begin the first trial immediately. The parameters that can be safely changed are listed below, along with their probable default values.
1. Number of trials per block (should be
multiple of 12):
(default=48)
2. Total number of blocks per session:
(default=6)
3. Duration of memory set exposure (msec):
(default=1200)
4. Number of practice blocks
(default=1)
5. Inter-trial interval (msec):
(default=1500)
6. Duration of error tone (msec):
(default=500)
7. Interval between memory set and probe (msec):
(default=500)
10. x location of stimuli (between 0 and 32000):
(default=16000)
11. y location of stimuli (between 0 and 32000):
(default=16000)
20. Maximum allowed reaction time (msec):
(default=3000)
Note: The size of the memory set on a given trial and the presence or absence of the probe digit are selected
randomly, subject to the constraint that there are an equal number of trials where the probe is present and absent for
each of the set sizes 1 - 6. The digits that comprise the memory set, and the order in which they are presented, are
selected randomly from the digits 1-9.
Analyzing the data (You will need analysis program available below)
Simply type SCANANAL and hit "Enter" from the directory in which the experiment was run. When asked "Number to trim from each end" the user has the option to exclude the desired number of extreme reaction times from the analysis. Hitting "Enter" will not exclude any data. To view the means from each condition TYPE or PRINT the file ASCAN.ANL. If you want to view the raw data, TYPE or PRINT the file DSCAN.DAT. Each time that MEMSCAN is run, the program will destroy all previous DSCAN.DAT data files. Each time that SCANANAL is run, it will destroy all old ASCAN.ANL files. Therefore, be sure to look at the data before the experiment is run again.