Discriminability of fixed-ratio schedules for pigeons: effects of payoff values

Three pigeons, previously trained to discriminate different numbers of responses (fixed ratios), were tested under different reinforcement contingencies (payoff matrices) at two levels of sensitivity. For one subject, relative reinforcement magnitude was varied—at first, across sessions and then, at midsession by reversing values—without exteroceptive cues. For another, relative reinforcement magnitude and/or probability was varied every 50 trials with cues by correlating different payoff matrices with different key colors. For the third subject, relative reinforcement probability was varied more frequently with cues—in the limit, at random—to demonstrate stimulus control of response bias on a trial-by-trial basis. A signal-detection analysis showed that bias changed with payoffs, for as many as seven different matrices, while sensitivity remained unchanged. The obtained functions (receiver operating characteristics) were similar under different payoff conditions, which suggests that a single mechanism controls bias. However, they differed enough in slope to require a relatively complex account (e.g., the general Gaussian model of detection theory).     

A Bayesian psychophysical model for angular variables

Bayesian theories of perception provide a link between observed response distributions and theoretical constructs from Bayesian decision theory. Using Bayesian psychophysics we derive response distributions for two cases, one based on a normal distribution and one on a von Mises distribution for angular variables. Interestingly, where the theoretical response distribution is always unimodal in the case of normal distributions, it can become bimodal in the angular setting in the case when prior and likelihood are about equally strong.     

Knowledge,Presupposition, and Pragmatic Implicature

It is widely accepted that knowledge is factive, but two different understandings of ＂factivity＂ should be distinguished, namely, the implication version and the presupposition version. While the former only takes the truth of P as a necessary requirement for ＂S knows that P,＂ the latter considers it also necessary for ＂S does not know that P.＂ In this paper, I argue against presupposition and defend implication. More specifically, I argue against Wang and Tai＇s defense of the presupposition version as presented in a recent paper and propose a pragmatic response to the ＂persistence problem＂ of implication. In other words, my positive proposal is an account of implication plus pragmatic implicature. To conclude, I use my version to analyze Wang and Tai＇s distinction between inner skepticism and outer skepticism. My conclusion is that, after abandoning presupposition, we can identify two types of intermediate skepticism between Wang and Tai＇s inner and outer skepticism.     

The analyst as a citizen in the world

Beginning with a ‘big dream’ from almost fifty years ago, this paper tracks movement back and forth from an inner/individual adaptation to life to outer/collective adaptations through various stages of a life's journey. The rhythm between more inner orientation at one stage gives way to more outer adaptation at another stage and vice versa. This same movement can be paralleled by an exclusive emphasis on analysis at one stage and more of a mixture of analysis and activism at another stage. At the heart of this narrative is the realization that an inner big dream of decades before, symbolised both an inner path of developing a relationship with life‐promoting energies and an outer path represented by facilitating others’ discovery and participation in those energies. The dream therefore anticipated a more activist future of connecting inner and outer, individual and collective in various professional projects. This has resulted in occasional glimpses of the fact that the ‘spirit of the depths’ and ‘the spirit of the times’ can have a common meeting ground.     

Adaptive criterion setting in perceptual decision making

Pigeons responded in a perceptual categorization task with six different stimuli (shades of gray), three of which were to be classified as "light" or "dark", respectively. Reinforcement probability for correct responses was varied from 0.2 to 0.6 across blocks of sessions and was unequal for correct light and dark responses. Introduction of a new reinforcement contingency resulted in a biphasic process of adjustment: First, choices were strongly biased towards the favored alternative, which was followed by a shift of preference back towards unbiased choice allocation. The data are well described by a signal detection model in which adjustment to a change in reinforcement contingency is modeled as the change of a criterion along a decision axis with fixed stimulus distributions. Moreover, the model shows that pigeons, after an initial overadjustment, distribute their responses almost optimally, although the overall benefit from doing so is extremely small. The strong and swift effect of minute changes in overall reinforcement probability precludes a choice strategy directly maximizing expected value, contrary to the assumption of signal detection theory. Instead, the rapid adjustments observed can be explained by a model in which reinforcement probabilities for each action, contingent on perceived stimulus intensity, determine choice allocation.     

The long and short of it: physical anchoring effects

Attempts to reconstruct the magnitude of recently encountered physical stimuli were influenced by the provision of physical anchors. Whether estimating length, weight, or loudness, those increasing the magnitude of a relatively small (short, light, or quiet) physical anchor produced estimates that were reliably lower than did those decreasing the magnitude of a relatively large (long, heavy, or loud) anchor. Estimates produced without an anchor were also low, suggesting that when people physically adjust upwards from a self‐selected starting point, “no anchor” may, in fact, act as a very low anchor. Physical anchors appear to influence estimates of recently encountered physical stimuli, much as numerical anchors influence estimates of more abstract numerical quantities. Implications for processes underlying anchoring, adjustment, and related tasks are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Psychophysics of Remembering: The Discrimination Hypothesis

In a psychophysical approach to remembering, the events to be remembered are discriminated from other possibilities at the time of remembering, and not at the time of encoding or learning. The discrimination is specific to the retention interval at which remembering occurs, as shown by experiments demonstrating that discriminability and response bias are delay–specific. This article discusses a discrimination model for remembering that emphasizes the individual's history of learning about reward payoffs in similar experiences in the past. This model predicts the two characteristics of forgetting functions, initial discriminability and rate of forgetting.     

DETECTION OF THE VELOCITY OF MOVEMENT OF VISUAL STIMULI BY PIGEONS

Nine pigeons were trained to discriminate a moving stimulus from a stationary stimulus. In one experiment, the stimulus was a rotating disc with radial stripes. In a second experiment, the stimulus was a vertically moving film strip with horizontal bars. Several psychophysical procedures were used to determine the minimal detectable velocity of movement. The detection thresholds for most of the pigeons fell in the range of 4.4 to 6.5 millimeters per second, corresponding to a retinal velocity of 4.1 to 6.01 degrees per second. A signal detection analysis of the psychophysical data indicated systematic changes in response bias that were related to the ordinal position of the stimulus velocity in the sequence.     

关于耳蜗传出神经系统功能研究的启示

耳蜗传出神经系统在听觉活动中的功能日益受到重视,本文以耳鼻喉专业知识为基点,查阅了近年一系列有关耳蜗传出神经系统的研究成果和趋势,从哲学层面总结出一些相关思考方式,期待运用这些思考方式与实践工作形成良好互动,指导实际的科学研究,有助于提高我们的专业思考潜力。