Immediate and Delayed Memory Tasks

The Immediate and Delayed Memory Tasks (available from Donald M. Dougherty, PhD, at NRLC@wfubmc.edu) are a set of computerized behavioral measures of impulsivity and attention. In the Immediate and Delayed Memory Tasks (IMT/DMT), individuals are instructed to click a mouse button when a target letter or number sequence appears on a computer monitor. Typically, five-digit numbers appear rapidly and briefly. When two consecutive sets of numbers appear and match (e.g., 19701 and 19701), individuals taking the test should click the button. These responses are interpreted as a measure of attention. However, in other trials, the numbers closely match but are not identical. Responses to these trials are interpreted as measures of impulsivity, because they are thought to reflect responding before information processing is completed.

The test is composed of two similar portions, the IMT and DMT, that differ in the length of time required to compare matching numbers. In both tasks, all number sets appear on the computer monitor for 0.5 second, with a 0.5-second break between numbers. In the IMT condition, individuals are instructed to compare successive stimuli, so that they must remember numbers spanning a 0.5-second period. But in the DMT, the numbers to be compared are separated by “distracters,” which are five-digit numbers presented three times between the numbers to be compared. For example, a DMT sequence could read 48593, 12345, 12345, 12345, 48593. As a result,[Page 453] the IMT requires remembering and comparing data for 0.5 second, whereas in the DMT, it is 3.5 seconds. Typically, the test is administered in four alternating testing blocks of IMT and DMT. The entire sequence takes about 20 minutes to complete.

In addition to the default testing conditions described here, this software package includes adjustable parameters allowing for testing across various samples and conditions. For instance, the IMT/DMT is suitable for assessment of children, adolescents, or adults; also, it is sensitive to state-dependent changes in impulsivity induced by situations such as drug use, medications, or stage of illness. The IMT/DMT is widely used in research settings, and it has excellent psychometric characteristics and extensive validity across a variety of populations.