Performing any behavior requires perceiving affordances-whether and how that behavior can be performed. Perception of affordances exhibits action scalingchoices about when to transition between two different modes of behavior reflect the fit between action capabilities and environmental properties. The boundary between distances that are perceived to be reachable with an arm-only reach and those that are perceived to be reachable with an arm-plustorso reach occurs at farther distances for long-armed than for short-armed people, but at the same ratio of objectdistance-to-arm length for both groups. To the extent that perception of affordances is supported by detection of invariant stimulation patterns, perception of a given affordance ought to exhibit action scaling regardless of species. We investigated the heights at which dogs chose to transition from reaching with the head only to rearing (i.e., reaching with the head plus torso). This transition occurred at a taller height for tall than for short dogs, but at the same ratio of shoulder-height-totreat-height for both groups. The results demonstrate a similarity in perception of affordances across species and suggest that perception of affordances is supported by detection of lawfully structured stimulation patterns that may be invariant across species.

Flexibility is a fundamental hallmark of perceptual systems. In particular, there is a great deal of flexibility in the ability to perceive properties of occluded objects by effortful or dynamic touch-hefting, wielding, or otherwise manipulating those objects by muscular effort. Perception of length of an occluded wielded object is comparable when that object is wielded by anatomical components that differ in sensitivity, dexterity, and functionality. Moreover, perception of this property is supported by an analogous sensitivity to inertial properties across such components. We investigated the ability to perceive whole and partial length of an object wielded by hand or by head. Experiment 1 found that perception of length by these anatomical components is qualitatively and quantitatively indistinguishable. Experiment 2 found that perception of length is supported by the same specific sensitivity to inertial properties in each case. Experiment 3 found that perception of whole length and partial length are each supported by specific sensitivities to inertial properties and that this is the case for both hand and by head. The results are discussed in the context of the nature of the stimulation patterns and the organization of the haptic system that are likely to support such flexibility in perception.

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Choices about when to transition between two modes of behaviour are determined by the fit between action capabilities and environmental properties. However, such transitions typically occur not at the absolute limits of action capabilities but rather based on the relative stability of each mode. People transition from an arm-only to an arm-plus-torso-reach, not when object distance exceeds arm length but when the stability of reaching with the arm-plus-torso exceeds that of reaching with the arm-only. To the extent that perception is supported by detection of invariant stimulation patterns, such a transition ought to reflect both the fit between action capabilities and environmental properties and the relative stability of modes regardless of species. We investigated the height at which dogs transitioned from reaching with the head-only to rearing when wearing a weighted backpack -a manipulation expected to decrease the stability of a headonly reach. As expected, the transition occurred at taller heights for tall than for short dogs but at the same ratio of treat-height-to-shoulder-height for both groups. This transition also occurred at shorter heights and smaller ratios of treat-height-to-shoulder-height when dogs wore a weighted backpack. The results suggest that stimulation patterns that support control of behaviour may be invariant across species.

Killen and Jacobs (2017) propose a new four-term operant contingency, in which an O (physiological/dispositional/motivational state of the organism) is added to the traditional three-term S-R-S r contingency. This fourth term is added in an attempt to explain changes in responding that may depend on the state of the organism responding for that reinforcer. We propose, instead, that an older model, the disequilibrium model (Timberlake & Farmer-Dougan, 1991), may already account for changes in such changes in responding. Further, the disequilibrium model may also predict the magnitude and direction of changes in responding across changing contexts.While reinforcement theorists ponder the function of the environment, discriminative stimuli, and the reinforcing event itself on the rate, magnitude, and probability of response, applied researchers struggle with finding a parsimonious explanation of reinforcement theory that is both experimentally and ecologically valid. Given the differing theoretical explanations and daunting terminology used to describe reinforcement, discerning an appropriate reinforcement model for an applied setting has become confusing. In our canine research, as well as previous work with humans, we see behaviorists in applied settings struggle with Bsimple^concepts such as the traditional four-square contingency, the Premack principle, and schedules of reinforcement. Indeed, a brief review of talks for the Karen Pryor Clicker Expo 2017, the online Association for Professional Dog Trainers discussion group, or even the BcBA Behavior Analyst Facebook group yields discussions on when to Buse Premack^versus positive reinforcement; how to distinguish