Stellar Prospector

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Summary

Tests focus on the Posner paradigm, distribution and shifting of attention, and the effect of multimodal (auditory and visual) stimuli.

Premise

The colony is in need of raw material resources. You are in control of the colony's Resource Gatherer. Use its tractor beam to collect as many resources as possible.

Objective

Collect as many resources as possible. Discard bad resources when they are detected.

Characters

Resource (Target Peripheral Stimulus):

File:ComingSoon.png

(Various Peripheral Distractor Stimuli):

File:ComingSoon.png

Specifications

The game screen is a semi-circle divided into a central (d1) sector, an intermediate (d2) arc, and 4 peripheral (d3) sectors.

Diagram.png

Central Stimulus

Sector d1 fills the player's visual field (1.78 degrees at a 50 cm viewing distance is 15.5 mm). This sector corresponds to all of the resources that have been gathered. It flickers at a rate of 10 frames per second. Every so often (about 20%), rather than having a peripheral stimulus appear, described further down, this central stimulus will turn from green to red. This will cue the player to press a key that correspond to the central stimulus to "fix the system" by getting rid of the bad iron, turning the central stimulus back to green.

Energy Indicator

The d2 region displays the current energy level of the resource gatherer. When the energy reaches the indicator's maximum level, the mini-game is complete.

Resource Detection System

One of the d3 sectors will always be outlined in red to signify an approaching resource. This resource detection system is fallible: 20% of the time, it cues an incorrect sector.

This aspect of the task implements a variation of the Posner attention paradigm (testing effects of cue validity and cue-target onset asynchrony) (Posner et al. 1987).

Peripheral Stimulus

The d3 sectors are monitors of outer space. (The diameter of sector d3 is currently equal to the width of the game screen - 800 pixels in the demo.)

Following the resource detection cue, a resource will appear in one of the d3 sectors.

The resource will slowly lose point value over time, disappearing over the duration of 6000 ms. A subtle particle effect will convey the resource as disintegrating.

Flashing

Each of the four sectors and the centre flash at one of five distinct frequencies. This flashing drives the visual system in the brain to resonance, just as any RC or LC electrical system can be driven to resonance by a periodic impulse at or near its resonant frequency. So flashing these five distinct areas of the display at five distinct frequencies will give five peaks in the spectrogram of the EEG recording. Attention modulates the amplitudes of these resonances - so for example if region A is flashing at 12 hz and region B is at 8.57 hz, when attention shifts from A to B we'll see the 12 hz spectral peak decrease and the 8.57 hz peak increase.

Different flash rates can be implemented by drawing and clearing the flashing stimulus for various numbers of frames when the display is operating at a known, constant frame rate. Differences in overall luminance integrated over time will arise from slightly unequal duty cycles when the number of frames is odd; these luminance differences can be compensated for by altering the intensity of the stimulus. For example, a frame rate of 60 hz would allow the following flicker frequencies:

frequency total frames frames on frames off intensity
15 hz 4 2 2 100%
12 hz 5 2 3 150%
10 hz 6 3 3 100%
8.57 hz 7 3 4 133%
6.67 hz 9 4 5 125%

These frequencies should be in the range 7 to 18 hz, approximately, and should be far enough away from each other to give distinct peaks in the spectrogram. (Notice that in the example above I've skipped the 8-frame cycle since its 7.5 hz frequency gets a bit too close to the neighbouring 8.57 hz and 6.67 hz frequencies.) In order to avoid contamination of one measurement with another, it is crucial that these flash frequencies not be harmonics of each other.

Gameplay

The player is inside the control room of the colony's resource gatherer.

There are two main tasks for the player:

1 - The player must respond, by pressing the Down arrow, when a bad resource is detected and displayed by the control panel.

2 - The player must respond, by pressing the Up arrow, when ore appears in any of the d3 sectors.

Phases

The peripheral task runs in three phases:

Phase 1: 100% of the stimuli appearing in the sectors are targets.

Phase 2: The same targets appear, but they are interspersed in time and space with many distractors (however many make the game feel right). Distractors are equally salient as targets, but distinguishable.

Phase 3: Same as Phase 2 but targets are paired with an alerting sound that is played whenever the detection cue in the d2 sector changes.


Scoring

Cash is awarded for each resource collected. (The cash values will be determined along with the Colony Simulator design)