A method for the objective study of tool-using behavior.
Positional fading can build complex tool use when shaping alone fails, and the response records itself.
01Research in Context
What this study did
Gladstone et al. (1975) worked with four crows. The birds had to use a stick to peck a key.
First the team tried plain shaping. The crows did not learn. Then they added positional fading. They moved the stick closer to the key over trials.
The setup let the computer count every stick-peck. No human had to watch and score.
What they found
All four crows learned the tool-use chain. Shaping alone had failed, but fading plus shaping worked.
The final response looked the same every time. The machine recorded it automatically.
How this fits with other research
Neumann (1977) used the same idea in a bathroom. A floating target autoshaped boys to aim. Both studies show positional cues can create new topographies without words.
Hart et al. (1968) showed monkeys key-press with pure autoshaping. W added fading, proving the method still works when the response is more complex than a simple peck.
da Silva et al. (2020) took the rule into speech therapy. They argue stimulus-stimulus pairing works best when it looks like autoshaping. The crow data give their claim cross-species muscle.
Why it matters
If a client can’t master a skill with direct prompting, slide the cue closer instead of talking more. Fade the position of the utensil, the switch, or the picture. Let reinforcement do the teaching while you track the response with a sensor or switch. Clean data, less chatter, faster acquisition.
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02At a glance
03Original abstract
Key pecking for food was shaped in four crows within a conventional operant-conditioning test chamber. When pecking stabilized, a metal screen with openings 2.5 cm high by 1.0 cm wide, was placed over the response key, so that the crow could still see but could no longer peck the key. At the same time, several dozen wooden matchsticks, which could be used to operate the key, were placed in the test chamber. The crows made no use of these during 50 to 75 hr of exposure to this condition. Subsequently, the behavior of two crows was shaped so that they approached the matchsticks, picked one up in their beaks, approached the response key with the matchstick in their beak, and finally operated the response key by poking the matchstick through the screen. This shaping procedure was ineffective with the two other crows. However, these birds were successfully trained through positional fading of the tool. This involved suspending a metal rod from the ceiling so that it hung directly in front of the response key, and the crow had only to peck it to operate the key. Then, the rod was gradually lowered by lengthening its tether until it eventually rested on the floor of the test chamber. The principal advantage of this methodology is the automatic recording of the terminal (tool-using) behavior under study.
Journal of the experimental analysis of behavior, 1975 · doi:10.1901/jeab.1975.24-249