In the experiment I'm composing the subject is shown a sequence of "Stimulus" instances, each for a specific duration, followed by a screen querying a response. I have code that seems to work fine, but I have a nagging suspicion that I may not be properly using the Vision Egg API, or overlooking a more straight-forward way of achieving the same thing. I'd appreciate any recommendations or tips anyone might have. Here's the basic structure: for t in numberOfTrials: Display fixation spot for 1 second Display a mask pattern for 3 frames @ 0.05s/frame Display a dot lattice for 0.3s Display response options and wait for subjeect to press a key I've structured my code such that each step is managed by a separate " Core.Stimulus" subclass, which in turn has its own viewport and presentation. The root of my question is whether I can be using the FlowControl classes or something else to do the following in a more elegant manner: fixation = FixationSpot(position=center) fixationView = Viewport(screen=screen, size=screen.size, stimuli=[fixation]) fixationPres = Presentation(go_duration=(1, 'seconds'), viewports=[fixationView]) lattice = DotLattice(position=center, dotSize=5) latticeView = Viewport(screen=screen, size=screen.size, stimuli=[lattice]) latticePres = Presentation(go_duration=(0.5, 'seconds'), viewports=[latticeView]) mask = DotLatticeMask(lattice) maskView = Viewport(screen=screen, size=screen.size, stimuli=[mask]) maskPres = Presentation(go_duration=(3, 'frames'), viewports=[maskView]) callbacks = [ (KEYDOWN, lambda event: response.keydown(event, responsePres)), ] response = ResponseVectors(position=center, lattice=lattice) responseView = Viewport(screen=screen, size=screen.size, stimuli=[response]) responsePres = Presentation(go_duration=('forever',), viewports=[responseView], handle_event_callbacks=callbacks) # Main experimentation loop for trial in conditions: lattice.setTrial(trial) fixationPres.go() maskPres.go() latticePres.go() responsePres.go() dataFileWriter.writerow(trial.values()) Basically, in contrast to the multiStim.py demo file which shows multiple stimuli at the same time, I want to know how to properly show multiple stimuli sequentially. Thanks, Simeon -- Simeon H.K. Fitch, Owner Mustard Seed Software http://www.mseedsoft.com/