Dependence of illusory motion on directional consistency in oblique components

Pinna and Brelstaff (2000 Vision Research 40 2091-2096) reported a motion illusion on viewing two concentric circles consisting of quadrangular components with black and white sides on a grey background. Our results suggest that the illusion is based on the integration of motion signals derived from oblique components, and on the consistency in the direction among those components. Furthermore, arrays of these oblique components can elicit the perception of motion not only for the oblique components themselves, but also for other objects in the picture. We propose that the motion illusion depends not only upon detection of the illusory motion signal at each local oblique component, but also upon the accumulation of the signal all over the stimulus configuration.     

Orthogonality is not a panacea: backpropagation and "catastrophic interference"

Connectionist models with the backpropagation learning rule are said to exhibit catastrophic interference (or forgetting) with sequential training. Subsequent works showed that interference can be reduced by using orthogonal inputs. This study investigated, with a more rigorous assessment method, whether all orthogonal inputs lead to comparable extent of interference using three coding schemes. The results revealed large differences between the coding schemes. With larger networks, dense inputs led to severer interference compared with sparse inputs. With smaller networks, all the three schemes led to comparable extent of interference. Therefore, this study proved that not all the orthogonal inputs cause the same extent of interference, and that severity of interference depends on the interaction of the input coding scheme and the network size.     

Evidence for model-based action planning in a sequential finger movement task

In this article, the authors examine whether and how humans use model-free, reflexive strategies and model-based, deliberative strategies in motor sequence learning. They asked subjects to perform the grid-sailing task, which required moving a cursor to different goal positions in a 5 × 5 grid using different key-mapping (KM) rules between 3 finger keys and 3 cursor movement directions. The task was performed under 3 conditions: Condition 1, new KM; Condition 2, new goal position with learned KM; and Condition 3, learned goal position with learned KM; with or without prestart delay time. The performance improvement with prestart delay was significantly larger under Condition 2. This result provides evidence that humans implement a model-based strategy for sequential action selection and learning by using previously learned internal model of state transition by actions.     

Integration of motion parallax with binocular disparity specifying different surface shapes

We investigated the interaction between motion parallax and binocular disparity cues in the perception of surface shape and depth magnitude by the use of the random dot stimuli in which these cues specified sinusoidal depth surfaces undulating with different spatial frequencies. When ambiguous motion parallax is inconsistent with unambiguous disparity cue, the reasonable solution for the visual system is to convert the motion signal to the flow on the surface specified by disparity. Two experiments, however, found that the visual system did not always use this reasonable solution; observers often perceived the surface specified by a composite of the two cues, or the surface specified by parallax alone. In the perception of this composite of the two cues, the apparent depth magnitude increased with the increase of the depth magnitude specified by both cues. This indicates that the visual system can combine the depth magnitude information from parallax and disparity in an additive fashion. The interference with parallax by disparity implies that the parallax processing is not independent of the disparity processing.     

Taste avoidance caused by spontaneous wheel running: effects of duration and delay of wheel confinement

Confinement of a rat in a running wheel results in the rat's subsequent avoidance of the taste consumed before the confinement. This phenomenon has been ascribed to taste aversion conditioned by spontaneous wheel running. As a first step toward clarification of the underlying mechanism of this phenomenon, we manipulated two parameters of the taste-confinement procedure: duration of wheel confinement (Experiments 1A and 1B) and temporal intervals between the taste consumption and the wheel confinement (Experiments 2A and 2B). In general, longer confinement and shorter inter-event interval caused stronger taste avoidance. However, the results also suggested that it is possible to establish taste avoidance when wheel confinement was delayed 1-h after the taste consumption. These results correspond to those of conventional taste aversion caused by illness-inducing agents, suggesting similar mechanisms in the both preparations. Experiment 3 revealed that running in a wheel rather than wheel confinement itself is the effective factor for establishing taste avoidance.     

A psychophysiological study on the function of the response‐stop in the Eriksen task1,2

Abstract: In the Eriksen task, we examined the hypothesis ( Iwaki, 1998 ) that a negative event‐related potential, which was enlarged at the frontal site synchronized with the presentation of an erroneous response causing stimulus, is related to the response‐stop function. Fourteen subjects responded selectively with their hands to the stimuli that consisted of a central target letter and surrounding compatible noise letters (e.g., HHHHH) or incompatible noise (e.g., SHHHS for small‐conflict condition or SSHSS for large‐conflict). The results showed that the increased negativity for the incompatible stimuli was synchronized with the stimulus onset but not with the response. Based on the hypothesis above, it is predicted that greater enhancement of an erroneous response by a stimulus causes the response‐stop to work harder in order to avoid an error, and this results in the larger negativity. This was supported by the evidence showing that the negativity was largest for the large‐conflict incompatible stimulus, followed by the small‐conflict, and then the compatible. We also discuss the possibility that the negativity is the NO‐GO potential concerned with the response‐stop function.     

A model of empty duration perception

An attempt to construct a general theory of duration perception is presented. First, four experiments are reported in which the supplement hypothesis, on the relation between two or three empty durations, was examined: the subjective duration of a subjectively empty time interval is directly proportional to its physical duration plus a constant of approximately 80 ms. This hypothesis could be applied to the ratio judgments of auditorily marked empty durations between 40 and 600 ms given serially. It could also explain the discrepancies between musically notated rhythms and the corresponding physical performed rhythms in very simple rhythm patterns consisting of three tones. Next, three earlier experiments on discriminations of empty durations marked by sound bursts were also reanalyzed. Within the range 40-600 ms, the absolute just noticeable difference of an empty duration was almost directly proportional to the standard duration plus a constant of about 80 ms. If the supplement hypothesis is accepted, this means that the relative just noticeable difference of the subjective duration was constant. Finally, the processing time hypothesis is presented: subjective duration is directly proportional to the physical time required to process the given empty duration. This processing is considered to begin with the detection of the first marker, and to end approximately 80 ms after the detection of the second marker.     

Correspondences among pupillary dilation response,subjective salience of sounds,and loudness

A pupillary dilation response is known to be evoked by salient deviant or contrast auditory stimuli, but so far a direct link between it and subjective salience has been lacking. In two experiments, participants listened to various environmental sounds while their pupillary responses were recorded. In separate sessions, participants performed subjective pairwise-comparison tasks on the sounds with respect to their salience, loudness, vigorousness, preference, beauty, annoyance, and hardness. The pairwise-comparison data were converted to ratings on the Thurstone scale. The results showed a close link between subjective judgments of salience and loudness. The pupil dilated in response to the sound presentations, regardless of sound type. Most importantly, this pupillary dilation response to an auditory stimulus positively correlated with the subjective salience, as well as the loudness, of the sounds (Exp. 1). When the loudnesses of the sounds were identical, the pupil responses to each sound were similar and were not correlated with the subjective judgments of salience or loudness (Exp. 2). This finding was further confirmed by analyses based on individual stimulus pairs and participants. In Experiment 3, when salience and loudness were manipulated by systematically changing the sound pressure level and acoustic characteristics, the pupillary dilation response reflected the changes in both manipulated factors. A regression analysis showed a nearly perfect linear correlation between the pupillary dilation response and loudness. The overall results suggest that the pupillary dilation response reflects the subjective salience of sounds, which is defined, or is heavily influenced, by loudness.     

Disentangling proactive and reactive aggression in children using self-report

The distinction between proactive and reactive functions of aggression is one of the most common divisions when investigating aggression among children and adolescents. To date, self-report is the least used measurement, despite existing literature supporting the view that the best informant regarding internal processes and motives are children themselves. The main aim of this study was to examine the construct and concurrent validity of a new self-report questionnaire, which aims to disentangle acts of reactive vs. proactive aggression that are most common within the daily lives of children. We examined the self-report measure among 578 children (313 girls, 265 boys, mean age 11 years, range 9–13 years). Most children (90% boys; 85% girls) reported at least one act of aggression over the last four weeks. Furthermore, the outcomes support the two-factor structure (reactive and proactive aggression) and the questionnaire showed good concurrent and discriminant validity with measures for emotional and social functioning. This study validates the use of the self-report instrument for reactive and proactive aggression and demonstrates that children can successfully distinguish between their own motives for reactive and proactive forms of aggressive behaviours.     

Renewal of Extinguished Lever-Press Responses upon Return to the Training Context

Two experiments with rats explored renewal effects in operant conditioning preparations. When pressing a lever was trained in one context and then extinguished in a second context, the responding was renewed by returning to the original context (ABA renewal) in Experiment 1. This finding was replicated in Experiment 2 with discriminative operant performance signaled by a localized light cue. In spite of the successful demonstration of ABA renewal effect in these experiments, AAB renewal was detected in neither experiment: When the responses had been extinguished in the context of acquisition, testing the rats in a second context did not renew the responses. The demonstration of ABA renewal but no AAB renewal suggests that extinction in another context and/or a return to the original context are critical for renewal of extinguished operant performance.