The Blip Machine — Which Ones Make It Go?

A home version of a famous child-development experiment: a pretend “machine” plays a sound only when certain objects are put on it, and the child works out which ones are the cause.

  1. Make the machine: an upturned shoebox with a paper “landing pad” on top. Hide a sound-maker you can work secretly — a bicycle bell or squeaky toy under the table, or a phone behind the box that you tap to play a jingle.
  2. Gather 6 small objects that differ in colour, shape and material (red block, blue block, spoon, sock, toy car, wooden peg). Secretly pick a rule — for example, “only wooden things make it go.”
  3. Place objects on the pad one at a time. If the object fits your rule, sound the “blip.” If not, silence. Do 3–4 objects while the child watches.
  4. Hold up an untested object and ask: “Will this one make it go? Why do you think so?” Then let the child put it on and find out.
  5. Let the child test the rest in any order they like. At the end ask: “So what makes the machine go?”
  6. Swap roles — the child invents a secret rule and works the sound, and you do the guessing (out loud, with a few wrong guesses).

Variation: put two objects on together (one that works and one that doesn’t) so the machine blips, then ask “Which one did it? How could we find out?” — the child has to test them one at a time.

Requirements

  • Space: A table top or a patch of floor
  • Surface: Table or floor where the child can sit opposite you
  • Materials: Shoebox, sheet of paper, 6–8 small household objects, a hidden sound-maker (bicycle bell, squeaky toy, or phone)
  • Participants: 1 adult + 1 child; a sibling can share the testing
  • Supervision: Full participation — the adult runs the machine

Rationale & Objective

This is a playful copy of the “blicket detector” task used by Alison Gopnik and colleagues, which showed that preschoolers can work out which objects have a hidden causal power from the pattern of what does and doesn’t set a machine off — and that they will sort objects by what they do rather than what they look like (Gopnik & Sobel, 2000; Gopnik et al., 2001). Deciding which object to try next, and pulling a pair apart to test each alone, is the beginning of the “change one thing” logic of experiments; Schulz & Bonawitz (2007) found preschoolers play longer and more purposefully exactly when the evidence is ambiguous. Stating the rule at the end practises Head Start ELOF’s analysing results and drawing conclusions, and HighScope’s predicting and drawing conclusions indicators.

Progress Indicators

  • Early: enjoys the sound but tests objects at random; predictions follow favourite objects or colours rather than the evidence; cannot yet say a rule
  • Developing: predictions start to match what was seen (“the block did it, so this block will too”); names one object that works, but not what the working objects share
  • Proficient: states the rule in their own words (“wooden ones make it go”); predicts untested objects correctly and gives a reason; when two objects are on together, suggests trying one at a time
  • Advanced: copes with trickier rules (two features, or “needs two things at once”); invents a consistent secret rule as the machine operator; notices and questions a result that doesn’t fit

Safety Notes

  • Choose objects too large to be a choking hazard if younger siblings are nearby
  • Keep the game light — it is a puzzle, not a test; if the child is frustrated, switch to an easier rule (a single colour) or swap roles
  • Some children are upset to learn the adult was working the sound; present it from the start as a pretend machine, or reveal the trick cheerfully and hand over the controls
  • A sudden loud bell or squeak can startle sound-sensitive children — use a soft sound and demonstrate it first

Hints

  • Playfulness: give the machine a name and a personality — it “loves” some things and ignores others. Use a robot voice to say “blip accepted”
  • Sustain interest: change the secret rule every time — colour, material, things that roll, things from the kitchen, things with holes
  • Common mistake: telling the child the rule when they guess wrong. Instead say “let’s test it” and let the machine answer — the evidence is the teacher
  • Limited space: no box needed — your open palm can be the machine and a hummed note the blip. Works in a waiting room with whatever is in your bag
  • Cross-domain: sort the objects into “makes it go” and “doesn’t” piles (classification); count each pile (numeracy); have the child explain the rule to another adult (language)
  • Progression: one obvious feature (colour) → a less visible feature (material, weight) → two objects on together → a rule needing two objects at once → child designs and runs the machine

Sources

  • Gopnik, A. & Sobel, D.M. (2000), “Detecting blickets: How young children use information about novel causal powers in categorization and induction,” Child Development, 71, 1205–1222
  • Gopnik, A., Sobel, D.M., Schulz, L.E. & Glymour, C. (2001), “Causal learning mechanisms in very young children,” Developmental Psychology, 37(5)
  • Schulz, L.E. & Bonawitz, E.B. (2007), “Serious fun: Preschoolers engage in more exploratory play when evidence is confounded,” Developmental Psychology, 43(4)
  • Head Start ELOF — Scientific Reasoning (makes predictions; analyzes results, draws conclusions, and communicates results)
  • HighScope Science & Technology KDIs — Experimenting, Predicting, Drawing conclusions
  • ASQ-3 — Problem Solving domain (54–60 month questionnaires)