The time course of figure-ground reversal

We report the results from five experiments employing a modified version of the short-term visual matching (STVM) method introduced by Driver and Baylis (1996). In STVM, participants see a study display with ambiguous figure-ground relations. After the study display, participants have to decide which of two shapes in a match display was seen before in the study display. STVM has been used by Vecera, Vogel, and Woodman (2002) to demonstrate that the lower region is a figure-ground cue. In our modified version of STVM, the study stimulus was preceded by a brief prime. This caused a biasing of the figural interpretation of the ambiguous figure-ground displays that contained the lower region cue. We show that 100-msec priming with an unambiguous display is enough to affect the subsequent interpretation of the ambiguous figure-ground display. It takes maximally 350 msec to complete a transition from the nondominant interpretation to the dominant interpretation of an ambiguous figure-ground display that contains the lower region cue.     

What time reversal invariance is and why it matters

David Albert's Time and Chance (2000) provides a fresh and interesting perspective on the problem of the direction of time. Unfortunately, the book opens with a highly non-standard exposition of time reversal invariance that distorts the subsequent discussion. The present article not only has the remedial goal of setting the record straight about the meaning of time reversal invariance, but it also aims to show how the niceties of this symmetry concept matter to the problem of the direction of time and to related foundation issues in physics.     

The effect of reinforcement probability on time discrimination in the midsession reversal task

We examined how biasing time perception affects choice in a midsession reversal task. Given a simultaneous discrimination between stimuli S1 and S2, with choices of S1 reinforced during the first, but not the second half of the trials, and choices of S2 reinforced during the second, but not the first half of the trials, pigeons show anticipation errors (premature choices of S2) and perseveration errors (belated choices of S1). This suggests that choice depends on timing processes, on predicting when the contingency reverses based on session duration. We exposed 7 pigeons to a midsession reversal task and manipulated the reinforcement rate on each half of the session. Compared to equal reinforcement rates on both halves of the session, when the reinforcement rate on the first half was lower than on the second half, performance showed more anticipation and less perseveration errors, and when the reinforcement rate on the first half was higher than on the second half, performance showed a remarkable reduction of both types of errors. These results suggest that choice depends on both time into the session and the outcome of previous trials. They also challenge current models of timing to integrate local effects.     

Transference,discrimination and reversal

A total of 68 subjects-17 normal volunteers, 17 hospitalized paranoid schizophrenics, 17 non-paranoid schizophrenics, and 17 patients with organic brain syndrome-were compared on their performance on the different phases of a specially devised conditioning procedure. This procedure is composed of (1) acquistion of the conditional reflex,i.e., squeezing a rubber bulb to the presentation of white light; (2) transference from a visual conditional stimulus to a verbal conditional stimulus and back to the visual conditional stimulus; (3) conditional stimulus differentiation; and (4) conditional stimulus reversal. Performance profiles of the normal and of the pathological groups were established and the statistically significant differences among the sub-groups of the experimental population were described. The clinical significance of these findings is discussed.     

The eyeglass reversal

Some figures, such as the Necker cube, are spontaneously reversible between alternative percepts. Before learning those skilled reversals, how do people achieve reversals for the very first time? It has been known that, in the case of a first reversal, peoplecan be expected to see the reversal when given specific information about how the figuresareambiguous. This point was confirmed by using drawing versions of reversible figures. To demonstrate how intention plays a role in the initial reversal of a real object, a pair of regular eyeglasses, reversible in perspective, were presented to naïve observers in monocular vision. When the eyeglasses were viewed inwardly and the observers were given information that the eyeglasses could be ambiguous, they were able to easily see the reversal. When the eyeglasses were viewed outwardly, observers saw it only after they had been informed of exactly what the two alternative percepts were.Interestingly, many observers often mistakenly saw the inwardly viewed eyeglasses as placed outwardly from the beginning of the observation, while they saw the outwardly viewed eyeglasses correctly. Taking these results together, for the first reversal of a real object, the specificity of intention varies with the ambiguity of the object.     

Vertical reversal and lateral reversal as components of inversion in recognition memory for upside-down faces

Subjects viewed upright photographs of faces, then attempted to recognize them unchanged, vertically reversed or inverted. In two of four conditions, hit scores were lower for inverted than vertically reversed faces, suggesting that lateral reversal is a meaningful component of inversion. The effect was not sufficiently strong, however, to overcome a generally high false-alarm rate for upside-down faces.     

Thermosensory reversal effect quantified

At room temperature, some materials feel colder than others due to differences in thermal conductivity, heat capacity and geometry. When the ambient temperature is well above skin temperature, the roles of ‘cold’ and ‘warm’ materials are reversed. In this paper, this effect is quantified by measuring discrimination thresholds for subjective coldness at different ambient temperatures using stimuli of different thicknesses. The reversal point was found to be at 34 °C, somewhat above skin temperature. At this reversal point, discrimination is quite impossible. At room temperature, subjects were able to discriminate between stimuli of different thickness based on subjective coldness, showing that the sense of touch, unlike vision, can penetrate solid objects. Furthermore, somewhat surprisingly, at ambient temperatures well below normal room temperature, discrimination is worse than at room temperature.     

Creativity and ease of ambiguous figural reversal

Two studies examined the relationships between self-rated and objectively measured creative ability and ease of perceiving alternative interpretations of the ambiguous Duck-Rabbit figure. The studies found empirical support for what has previously been a largely analogical connection between figural reversal and creativity, using both self-rated trait creativity and objectively scored creative productivity. We discuss the hypothesis that executive functioning is the likely common cognitive factor linking perception of ambiguous figures and creative ability.     

Habit reversal in the turtle

Two groups of mature “painted” turtles were trained in a T-maze. One group had five trials per day, with correct and incorrect turns reversed for each animal whenever it reached the criterion of five errorless trials on a given day. The second group had 10 trials per day, with correct and incorrect turns reversed daily, irrespective of the performance of the animals. Only in the data for the second group did there appear some indication of progressive improvement in habit reversal. The results are considered in relation to those obtained in analogous experiments with other species.     

Sequential effects on discrimination reversal

In Experiment 1 the sequence of trials to the positive (S+) and negative (S?) discriminanda was varied between groups during acquisition and reversal of a successive brightness discrimination. In Experiments 2 and 3, groups received different reward sequences in Phase 1 within S+. In general, groups given transitions from nonrewarded trials to rewarded trials (N-R transitions) in Phase 1 learned both the original discrimination and its reversal more slowly than groups given schedules devoid of N-R transitions. The results were discussed in relation to previously reported effects of partial reinforcement on acquisition and reversal of a discrimination and the role of sequential variables and internal, reward-produced cues in discrimination learning, reversal learning, and nonreversal shifts.     

Habit reversal treatment of thumbsucking

About 40% of young children suck their thumbs, an action which is associated with dental problems and for which intra-oral devices have been the most effective treatment. The present study of 30 thumbsucking children evaluated the habit reversal treatment which included competing response training, parental support, and stimulus identification during a single session plus follow-up maintenance by the parent. Habit reversal training reduced thumbsucking by 92% in the first week, 95% in the fourth month, and 89% at the 20-month follow-up. A comparison treatment by a bitter tasting substance produced a reduction of about 35%.