Final answer:
The peak response rate for a pigeon trained with an SΔ at 550 nm and an SD at 530 nm would most likely be at 530 nm, as it is the conditioned discriminative stimulus for which the pigeon was trained to respond.
Step-by-step explanation:
The peak response rate observed during generalization testing for a pigeon trained with an SΔ at 550 nm and an SD (discriminative stimulus) at 530 nm would most likely be at 530 nm. This is because the SD is the stimulus that the pigeon has been conditioned to respond to, whereas the SΔ is the stimulus that the pigeon has learned not to respond to. The generalization gradient would peak at the SD wavelength. Light in this part of the spectrum is considered to be in the yellow-green range, and due to the pigeon's previous training, the response is likely to be strongest at the wavelength of the SD rather than at 550 nm or an intermediate wavelength.