An inexpensive infrared detector to verify the delivery of food pellets.
Add a twenty-five-dollar infrared pellet eye to any operant box and you will know every reinforcer really arrived.
01Research in Context
What this study did
Braam et al. (2008) built a tiny infrared eye that watches the food cup.
The eye costs about twenty-five dollars and screws onto any operant box.
When a pellet lands, the eye sees it and sends a quick yes signal to your computer.
What they found
The sensor never missed a pellet in the lab test runs.
It also never cried wolf when no pellet dropped.
That means your data stay clean and your rats get every reinforcer they earn.
How this fits with other research
Gurley (2019) took the same penny-pinching idea even further. That team built an entire Raspberry Pi chamber for under two hundred dollars, so you can now run a full study with open-source parts.
Hulse (1960) and DAVIS (1961) did the same thing for drinks. Their circuits counted licks and drips back when transistors were new, proving that cheap hacks have a long track record in operant work.
Carman (1976) used a low-tech float to spot low water bottles. Like the pellet eye, it lets you check consumables without opening the cage, showing that simple fixes keep animals healthy and data honest.
Why it matters
If you run rodent studies, a missed pellet means lost behavior and bad graphs. For the price of a pizza you can bolt this sensor on your old box and never wonder again. Your graphs, your students, and your IACUC will all thank you.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Order a five-dollar IR LED and photodiode, solder the wires, tape the pair above the food cup, and log the extra channel in your next session.
02At a glance
03Original abstract
The reproducibility of experimental outcomes depends on consistent control of independent variables. In food-maintained operant performance, it is of utmost importance that the quantity of food delivered is reliable. To that end, some commercial food pellet dispensers have add-on attachments to sense the delivery of pellets. Not all companies, however, offer such add-ons. Aside from availability, cost and temporary reduction in throughput may be a problem for smaller labs. The present paper outlines our recent development of a simple, inexpensive infrared device to detect and confirm the delivery of pellets. The in-line construction of the detector routes the falling pellet through a barrel so that it passes between an infrared emitter and receiver. The circuitry was designed to be compatible with all commercially available behavioral measurement systems, and so may be retrofit to any existing system. Our tests with the detector so far have shown that it is 100% accurate in detecting pellet delivery. The individual unit cost is approximately 25 dollars. The low cost and versatility of the device offer an easy method to ensure the integrity of food delivery in operant settings.
Journal of the experimental analysis of behavior, 2008 · doi:10.1901/jeab.2008.90-249