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Interactive Activation and Competition Model ​

This is an interactive demonstration of the Jets and Sharks network from Rumelhart & McClelland (1986). The network illustrates how knowledge can be retrieved through spreading activation in a connectionist model. This demo is based on the IAC application by Axel Cleeremans.

Cycle: 0
FeaturesNamesHiddenGangAgeEducationMaritalOccupationJetsSharks20s30s40sJHHSCOLSingleMarriedDivorcedBookieBurglarPusherArtAlSamClydeMikeJimGregJohnDougLanceGeorgePeteFredGeneRalphPhilIkeNickDonNedKarlKenEarlRickOlNealDave
Global Change:0.000000
Click units to activate | Space to play/pause | R to reset

The Network ​

The network has three pools of units:

  • Features (outer ring): 14 units representing properties like gang membership (Jets/Sharks), age (20s/30s/40s), education (JH/HS/COL), marital status, and occupation
  • Names (middle ring): 27 units representing individual people
  • Hidden (inner ring): 27 internal representation units

Connection Rules ​

  • Between pools: Bidirectional excitation (+1)
  • Within pools: Lateral inhibition (-1)

How to Use ​

  1. Click on any unit to provide external input (activation). The unit will glow green when activated.
  2. Click again to remove the external input.
  3. Use Play/Pause to run or stop the simulation.
  4. Use Step to advance one cycle at a time.
  5. Hover over any unit to see its connections and current values.
  6. Press Space to toggle play/pause, R to reset.

Try These Examples ​

Example 1: Who is Art? ​

Click on "Art" in the Names ring and press Play. Watch as his features (Jets, 40s, JH, Single, Pusher) become activated in the outer ring.

Example 2: Who is in their 20s with only Junior High education? ​

Click on "20s" and "JH" in the Features ring. The hidden units for Jim, John, Lance, and George should show the highest activation - these are the only people with both properties.

Example 3: What gang are young people likely in? ​

Click only on "20s" and watch. The Jets unit should activate more strongly than Sharks because 9 Jets members are in their 20s versus only 1 Shark.

IAC Equations ​

The network uses the following update rules:

Net Input:

netInput = alpha * excitation + gamma * inhibition + estr * extInput

Activation Update:

if netInput > 0:
  delta = (max - activation) * netInput - decay * (activation - rest)
else:
  delta = (activation - min) * netInput - decay * (activation - rest)

Parameters: max=1.0, min=-0.2, rest=-0.1, decay=0.1, alpha=0.2, gamma=0.1, estr=0.4

References ​

Rumelhart, D. E., & McClelland, J. L. (1986). Parallel Distributed Processing: Explorations in the Microstructure of Cognition. MIT Press.

See also the PDP Handbook for more details.