A variant of the anomalous motion illusion based upon contrast and visual latency

We examined a variant of the anomalous motion illusion. In a series of experiments, we ascertained luminance contrast to be the critical factor. Low-contrast random dots showed longer latency than high-contrast ones, irrespective of whether they were dark or light (experiments 1 -3). We conjecture that this illusion may share the same mechanism with the Hess effect, which is characterised by visual delay of a low-contrast, dark stimulus in a moving situation. Since the Hess effect is known as the monocular version of the Pulfrich effect, we examined whether illusory motion in depth could be observed if a high-contrast pattern was projected to one eye and the same pattern of low-contrast was presented to the other eye, and they were binocularly fused and swayed horizontally. Observers then reported illusory motion in depth when the low-contrast pattern was dark, but they did not when it was bright (experiment 4). Possible explanations of this inconsistency are discussed.     

Additivity of retinal and pursuit velocity in the perceptions of depth and rigidity from object-produced motion parallax

Two psychophysical experiments were conducted to investigate the mechanism that generates stable depth structure from retinal motion combined with extraretinal signals from pursuit eye movements. Stimuli consisted of random dots that moved horizontally in one direction (ie stimuli had common motion on the retina), but at different speeds between adjacent rows. The stimuli were presented with different speeds of pursuit eye movements whose direction was opposite to that of the common retinal motion. Experiment 1 showed that the rows moving faster on the retina appeared closer when viewed without eye movements; however, they appeared farther when pursuit speed exceeded the speed of common retinal motion. The 'transition' speed of the pursuit eye movement was slightly, but consistently, larger than the speed of common retinal motion. Experiment 2 showed that parallax thresholds for perceiving relative motion between adjacent rows were minimum at the transition speed found in experiment 1. These results suggest that the visual system calculates head-centric velocity, by adding retinal velocity and pursuit velocity, to obtain a stable depth structure.     

Seeing double and depth with Wheatstone's stereograms

Charles Wheatstone, in his classic paper on the invention of the stereoscope, concluded "... objects whose pictures do not fall on corresponding points of the two retinae may still appear single" (1838 Philosophical Transactions of the Royal Society of London 128 384). Soon after, Ernst Brücke, Alexandre Prévost, David Brewster, Joseph Towne, and Joseph LeConte all published disagreements with this conclusion. LeConte's objections were most frequent and most prolonged. To understand the basis of the disagreements, we conducted three experiments using Wheatstone's original stereograms and found that most stereograms produced depth perception with diplopia, which partially explains the consistency among his critics' conclusions. Most of the criticism at variance with Wheatstone's conclusion was based on research conducted outside Germany. We argue that LeConte's lack of knowledge of the German literature on vision research prevented him from considering investigating Wheatstone's experiment with a stereogram having a smaller disparity.     

Children perseverate to a human's actions but not to a robot's actions

Previous research has shown that young children commit perseverative errors from their observation of another person's actions. The present study examined how social observation would lead children to perseverative tendencies, using a robot. In Experiment 1, preschoolers watched either a human model or a robot sorting cards according to one dimension (e.g. shape), after which they were asked to sort according to a different dimension (e.g. colour). The results showed that children's behaviours in the task were significantly influenced by the human model's actions but not by the robot's actions. Experiment 2 excluded the possibility that children's behaviours were not affected by the robot's actions because they did not observe its actions. We concluded that children's perseverative errors from social observation resulted, in part, from their socio-cognitive ability.     

The effect of repeated writing on memory

Repeated writing, or rehearsal by writing, is a common memory strategy for the Japanese, especially when learning new logographic characters. The to-be-remembered items are written down not as external prompts, as with reminder notes, but to be memorized in the course of writing them down over and over again. In this study, we investigated whether the strategy was effective, and if so, in which condition. Experiment 1 showed that repeated writing improved memory for graphic designs but not for Chinese characters, words, or syllables. Experiment 2 showed that the effect occurred for both Japanese and American subjects, suggesting that it was not the result of a cultural background associated with a logographic language. Instead, the effect seemed to be accounted for by the encoding specificity of visual-motor information, because repeated writing improved free recall— that included writing—but did not improve recognition (Experiment 3). In Experiment 4, the strategy was applied to learning the Arabic alphabet. Finally, similarities between repeated writing and     

Effects upon rats' responses on a running wheel of single alternation of large and small rewards and external cues

Thirty-two rats were trained to run on a running wheel for one or six pellets of food, in either single alternation (SA) or quasi-random sequences of reward magnitude and with external cues either informing or not informing the rats of the reward magnitude. Reward-magnitude discrimination was clearly shown when the informative cues were given, but without such cues the SA patterning of responding appeared only late in training. The reward-magnitude discrimination developed most quickly when internal (SA) cues and external informative cues were both present; the effects of these two classes of cues on discrimination were interactive rather than additive. Possible explanations are given for the superior discrimination under the condition where both the internal and external cues were present over the condition when only the external cues were present.     

World‐Pictures and Wittgensteinian Certainty

Although certainty is a fundamental notion in epistemology, it is less studied in contemporary analytic epistemology than other important notions such as knowledge or justification. This paper focuses on Wittgensteinian certainty, according to which the very basic dimension of our epistemic practices, the elements of our world‐pictures, are objectively certain, in that we cannot legitimately doubt them. The aim of the paper is to offer the best philosophical way to clarify Wittgensteinian certainty, in a way that is consonant with Wittgenstein's fundamental insights. The paper critiques two alternative proposals for clarifying Wittgensteinian certainty that are philosophically unsatisfying: the rule view and the proposition view. Finally, it instead shows how viewing world‐pictures as pictures, in the sense of unclear conceptions, is a more philosophically fruitful approach to understanding world‐pictures.     

The effect of on‐ or off‐line extinction of a first‐order conditioned stimulus on a second‐order conditioned response in rats

In a water‐licking experiment with rats, the effects of the extinction of a first‐order conditioned stimulus (CS1) on the suppression of licking established for a second‐order conditioned stimulus (CS2) were explored. Extinction of the first‐order conditioned response (CR1) attenuated the conditioned suppression induced by CS2 when the rats had been allowed to lick water during the CR1 extinction phase. However, if water had been unavailable during the CR1 extinction phase, suppression by CS2 was not affected. The latter result is consistent with other studies of rats' conditioned suppression and suggests that the underlying mechanism of second‐order conditioning in this experiment is a connection between CS2 and the response elicited by CS1 rather than a CS2‐CS1 connection. The former result was interpreted as the CR1 extinction phase encouraging the rats to lick water despite the fear elicited by CS1, and thus, in testing, they licked despite the fear elicited by CS2.