Operant Chamber for Pigeon Cognition

Pigeons were trained and tested in an operant chamber measuring 80 cm (height), 54 cm (width), and 56 cm (depth). The chamber was insulated with acoustic foam to reduce ambient noise. Additionally, a ventilator generated constant background noise in the chamber. The operant chamber was further equipped with copper mesh to shield against electromagnetic noise (a Faraday cage) and a surveillance camera. During the testing sessions, the door of the operant chamber was closed, and an LED strip on the ceiling (“house light”) dimly illuminated the chamber. The birds stood on a wooden perch, facing a 54 by 40 cm acoustic pulse touchscreen monitor (Elo Touch Solutions), which displayed the stimuli and detected responses. A custom pellet feeder, which dropped individual pellets (BioServ) into a small feeding trough, delivered food rewards, which were illuminated during the reward period. All aspects of the behavioral task were controlled by a PC using MATLAB (2016a; MathWorks) and the Biopsychology and Psychophysics Toolboxes (Brainard, 1997 (link); Rose et al., 2008 (link)). We used a custom ethernet-based digital input/output (I/O) device to control the feeder and lights while also sending event codes to the neurophysiology hardware (code and plans are freely available online at https://www.ngl.psy.ruhr-uni-bochum.de/ngl/shareware/index.html.en).