This tutorial demonstrates how to set up a gamified test of Spatial Anticipation where participants are asked to estimate the time when objects would collide on the screen. The objects can move at different speed and their movement can be hidden for various durations.
First, we create two objects with Animated Sprites: BallLeft and BallRight. We add animations Move To Object that move the balls to two points in the middle of the screen (hotspotL and hotspotR) where balls 'collide'. We determine the duration of the animation, i.e. the time that it takes the balls to move, by binding it to Spreadsheet columns BallLeftDuration and BallRightDuration - this allows us to vary the speed for each ball per trial.
We hide the balls at certain points of their movement using Quads coloured the same as the background so that it looks like the balls 'disappear' while in reality they hide behind Quad objects. We place Quads in front of other objects by placing them lower on the list of Objects (the lower down the list, the more forward to the viewer the objects appear). You can vary the sizes of the quads, like in the display 'collide2'.
We add a Keyboard response component for participants to respond with Space press when they think the objects would 'collide'. As a default, the Space response would progress the screen, however, we want to calculate the difference between the actual 'collision' time and perceived 'collision' time so we need to play the whole animation, while also recording participants' reaction time (RT). Therefore, in the Screen tab we add Advance - Accuracy (TimeOut and Continue) component which makes Gorilla to only advance on TimeOut from a Time Limit component (or a Continue button - not relevant in our case). The time limit is bound to spreadsheet column 'ScreenTimeLimit' to vary it between trials. It is important to set up the time limit to be sufficiently longer than the actual 'collision' time to account for a scenario when participants' RT is longer than the 'collision' time.
As a result, we have a test where two objects move towards each other and 'disappear' at some point, participant responds when they think the objects would 'collide', and we record participants' RT. In the data, we can calculate the difference between the actual 'collision' time and perceived 'collision' time by subtracting participants' RT from the BallRight/BallLeftDuration.