Affordances as constraints on the control of stance

In this article we present an ecological treatment of the control of stance by multi-segment organisms. We treat the organism as a black box, and the organism-environment interaction as a closed-loop system. We argue that different ways of controlling stance can have differing utility (affordances) for perception and action. We further argue that the affordances of a particular control strategy are in part determined by (a) the mechanical properties of the organism, (b) the mechanical properties of the surface on which stance takes place, and (c) the goals of behavior. Our conclusion is that the control of stance is based on, or constrained by, perception of the kinematic consequences, or affordances, of control actions. Finally, we argue that the relationship between affordances and constraints on control actions should be investigated using geometrical methods.     

Forgetting of stimulus attributes: methodological implications for assessing associative phenomena.

Differential responding to changes in the stimulus situation, long central to the concept of stimulus control, also provides the implicit conceptual basis for assessing the nature of a variety of associative relationships. However, there is substantial evidence that the perception of stimulus similarity is not a static property. Generalization gradients to contextual as well as discriminative stimuli flatten over time, and this increase in perceived similarity presumably reflects forgetting of the detailed characteristics or attributes of stimuli. Methodologically, the flattening of the gradient imposes an important constraint: The effect of a stimulus shift will be highly sensitive to the length of the delay interval between training and testing. Conceptually, the loss of memory for stimulus attributes also implies that the sources of interference in retention can increase over time.     

The Importance of Context in the US Preexposure Effect in CTA: Novel versus Latently Inhibited Contextual Stimuli

Three experiments were conducted to examine the role of novel contextual stimuli in producing the unconditioned stimulus (US) preexposure effect. Experiment 1 demonstrated that novel contextual stimuli produce a significantly stronger US preexposure effect than familiar or “latently inhibited” contextual stimuli. Moreover, subjects preexposed in the presence of latently inhibited contextual cues failed to show a significant US preexposure effect. Experiments 2 and 3 attempted to provide evidence that the addition of a single novel stimulus to the latently inhibited context would result in a significantly stronger US preexposure effect than when no such novel cue was present. Experiment 3 was able to demonstrate this effect. Results are consistent with the Rescorla–Wagner (1972) model of conditioning.     

Manipulation of Components of Context: The Context Shift Effect and Forgetting of Stimulus Attributes

Seventy-two Sprague–Dawley rats were used to investigate the multidimensional features of the context shift effect and the forgetting of stimulus attributes in a Pavlovian differential fear conditioning paradigm. One day after training, a change in either conditioning box or room context resulted in substantial decrements in performance similar to that induced by a shift of both box and room contexts. Two weeks after training, a shift of either box or room context exerted no significant detrimental effects on responding. However, a combined shift of both box and room contexts still induced a severe performance deficit. These results suggest that changes in various components of the stimulus context can result in similar retention deficits, that several aspects of stimulus attributes are forgotten over a delay, and that changing several aspects of the stimulus complex can synergistically impair performance.     

Extinction of avoidance behavior and the problem of residual fear

According to two-factor theory, avoidance responding is predicated on a conjoint relationship between Pavlovian and instrumental conditioning. Recently a variety of evidence has indicated that these processes are independently subject to experimental manipulations, both during acquisition and extinction. The latter finding is paralleled in the clinicial literature by the observation that the elimination of an avoidance response does not adequately reflect concurrent changes in autonomic and verbal behavior. These findings suggest the need for multiple measures of anxiety in assessing the effect of experimental and therapeutic operations on avoidance behavior. This paper also calls attention to the discriminative and reinforcing properties of the CS in an attempt to account for these findings.     

d-Cycloserine: effects on long-term retention of a conditioned response and on memory for contextual attributes.

d-Cycloserine (DCS), a partial agonist of the glycine recognition site of the N-methyl d-aspartate receptor, has beneficial effects on learning and memory. In order to investigate its potential to influence learning and memory of both the response and the stimulus attributes of training, male Sprague-Dawley albino rats were trained in a one-trial inhibitory avoidance task following an acute intraperitoneal injection of DCS (3 mg/kg) or an equal volume of saline. In order to measure memory for stimulus attributes, testing involved a context shift paradigm, in which subjects are tested in either the environment of training or a different one. Good memory for the contextual attributes of training is indicated by poor performance in the alternate context. Retention was assessed either 1, 7, or 14 days after training. At 1 day, Saline subjects were affected by a change in context, while DCS subjects were not. In subjects tested 1 week following training, Saline subjects were no longer affected by a change in context, in that they performed the avoidance response in both contexts. This indicates the forgetting of stimulus attributes in Saline subjects. DCS subjects did show the context shift effect at 1 week, indicating the retention of stimulus attributes. Finally, Saline subjects demonstrated the context shift rebound at 14 days, while DCS subjects performed equivalently in both contexts. Taken together, these data suggest that DCS may enhance retention of fear and slow the forgetting of stimulus attributes.     

非期望刺激的生态意义信息对无意视盲的影响:情绪效价和精细程度的作用

采用Most(2000)的持续动态的实验范式,以圆圈、抽象面孔和真实面孔为非期望刺激,研究其生态意义信息对无意视盲的影响。研究发现:(1)相对于正性面孔和中性面孔,被试对负性面孔作为非期望刺激时的觉察率更高;而对正性面孔和中性面孔作为非期望刺激时的觉察率无显著性差异;(2)相对于圆圈,抽象面孔和真实面孔作为非期望刺激的觉察率更高,而抽象面孔与真实面孔作为非期望刺激时的觉察率均无显著性差异。结果表明,负性的、精细的非期望刺激的无意视盲率更低,即生态意义信息强的非期望刺激更易捕获注意。