# Sequence items

In an experiment you will often have a number events that occur sequentially. For example, you may present, in each trial, a fixation point, followed by a number of stimulus displays and, finally, perform response collection and response logging. This is where the sequence item comes in. Another use for a sequence is as the 'main sequence' of the experiment.

## Order of the sequence

Sequence items are run from top to bottom, i.e. the first item is the item that is presented at the top. You can move and remove sequence items using the corresponding buttons on the right of the tab. You can remove items from the sequence by clicking on the Remove button. This removes the item only from the current sequence.

## Appending items to the sequence

You can add items to the sequence by clicking on the buttons at the bottom of the tab. The Append existing item button appends an entry to the sequence table, but does not create a corresponding new item. This way you can add a single item (a fixation dot display, say) multiple times to a sequence. The Append new item button creates a new items and appends it to the sequence.

## Conditional statements (run if...)

A very convenient feature of the sequence item is that you can use conditional ('if') statements. For example, if you want a display to be presented only if a participant has made an incorrect response (during a previously called keyboard_response or mouse_response item), you can add '[correct] = 0' to the Run if entry of your item (for example, a sketchpad containing the text 'pay attention!'). If you leave the Run if entry empty or enter 'always', the item will always be called.

Examples of valid conditional statements are (note that no quotes are required and that variable names should be placed between square brackets):

- always

- never

- [variable_name] = value

- [variable_name] != value or [another_variable_name] = another_value

- 2 > 1 and 1 < 2

For more information about conditional statements, go to <http://osdoc.cogsci.nl/usage/variables-and-conditional-qifq-statements>.