The Intra-Extra Dimensional set-shift (IED) task assesses the processes involved in categorising stimuli into sets (visual discrimination of shapes vs. lines), and responding flexibly (shifting attention) to changes in stimuli.
The IED task requires participants to learn the rule and select the correct icon (a specific shape or line). The task builds in complexity as distractors are added and the rule changes. The rule changes are both intra-dimensional (e.g. shapes are still the relevant set, but a different shape is now correct) and extra-dimensional (e.g. shapes are no longer the relevant set, instead one of the line stimuli is now correct). Figure 1 provides a clip of the task in action.
Figure 1. Video-clip of IED.
The task allows the maintenance and flexibility of attention to be assessed. These insights into attentional processes have been applied to the identification of selective impairments both within- and between- diagnostic categories.