Asking an eyewitness to describe a suspect's physical appearance to a sketch artist would be an example of a task, whereas asking an eyewitness to identify a suspect on the basis of a lineup of five possible assailants is an example of a task.

Asking an eyewitness to describe a suspect's physical appearance to a sketch artist would be an example of a RECALL task,

whereas asking an eyewitness to identify a suspect on the basis of a lineup of five possible assailants is an example of a RECOGNITION task.

Explanation:

Recall versus Recognition:

Sometimes we walk in town and you meet this person and you feel that their face is familiar but you can't seem to remember their name this is recognition. Recognition means we can recognise that a subject is familiar eventhough we can't really remember their particulars. Recall means we retrieve details associated with a particular event.

These two memory retrieval differ from each other by cues available to assist us retrieve memory, recall has less cues than recognition; all the cues in recognition makes it easier to retrieve memory for the fact that you can see what you are asked to remember rather than trying to figure it out in your mind as in recall.

For example in multiple choice questions it is easier to remember when you see all the choices to pick from cause you start to recognise what you studied but in an open question it's different because you have to try and remember what you have studied and try to bring it back in your mind.