The rubber hand illusion in a mirror

In the rubber hand illusion (RHI) one’s hand is hidden, and a fake hand is visible. We explored the situation in which visual information was available indirectly in a mirror. In the mirror condition, compared to the standard condition (fake hand visible directly), we found no reduction of the RHI following synchronised stimulation, as measured by crossmanual pointing and by a questionnaire. We replicated the finding with a smaller mirror that prevented visibility of the face. The RHI was eliminated when a wooden block replaced the fake hand, or when the hand belonged to another person or mannequin. We conclude that awareness of the reflection is the critical variable, despite the distant visual localisation of the hand in a mirror and the third-person perspective. Stimuli seen in a mirror activate the same response as stimuli seen in peripersonal space, through knowledge that they are near one’s body.     

Discrimination of color and pattern novelty in one-month human infants

Visual discrimination of novel colors and patterns by one-month infants was studied in two experiments where visual reinforcers were presented contingent upon infants' rate of nonnutritive, high-amplitude sucking. Discrimination was measured by recovery of sucking to the presentation of novel visual reinforcing stimuli following decrements in sucking to familiar visual stimuli. In Expt 1, following decrement to familiar stimuli, independent groups received either a change in color, pattern, both color and pattern, or no stimulus change. Reliable recovery was demonstrated for the three stimulus novelty groups relative to the no-change control. Experiment 2, employing achromatic visual reinforcers also showed reliable recovery to pattern change relative to no-change controls. These findings with one-month infants indicate discrimination between familiar and novel visual reinforcers on the basis of color and pattern differences and an increase due to novelty in the reinforcing effectiveness of visual stimuli. Individual subject differences in response decrement magnitude during familiarization were positively correlated with amount of response recovery to novelty.     

Replacing relative reinforcing efficacy with behavioral economic demand curves

Relative reinforcing efficacy refers to the behavior-strengthening or maintaining property of a reinforcer when compared to that of another reinforcer. Traditional measures of relative reinforcing efficacy sometimes have led to discordant results across and within studies. By contrast, previous investigations have found traditional measures to be congruent with behavioral economic measures, which provide a framework for integrating the discordant results. This study tested whether the previously demonstrated congruence between traditional relative reinforcing efficacy measures and behavioral economic demand curve measures is sufficiently robust to persist when demand for one reinforcer is altered. Cigarette smokers pulled plungers for cigarettes or two magnitudes of money on progressive-ratio schedules that increased the response requirement across sessions. Demand for the two different reinforcers was assessed in single-schedule and concurrent-schedule sessions. Demand curve measures Pmax and Omax correlated significantly with traditional measures of breakpoint and peak response rate, respectively. Relative locations of demand curves for money and cigarettes under single schedules predicted preference in concurrent schedules in most cases. Although measures of relative reinforcing efficacy for money changed with money magnitude, the congruence between traditional and behavioral economic measures remained intact. This robust congruence supports the proposal that demand curves should replace measures of relative reinforcing efficacy. The demand curve analysis illustrates why concordance between traditional measures is expected under some experimental conditions but not others.     

Discriminative and reinforcing properties of paintings in Java sparrows (<Emphasis Type="Italic">Padda oryzivora</Emphasis>)

Previous studies suggest that non-human animals can discriminate two different artworks (such as music or paintings) that were created by humans. However, such studies rarely examined whether those animals were reinforced by one artwork more than another. It has been shown that music composed by humans has both discriminative and reinforcing properties when played for Java sparrows. Here, we investigated the effects of another artistic medium in Java sparrows, namely paintings. The first experiment tested the reinforcing properties. Staying time at three painting categories—Japanese, cubist, and impressionist—was measured as an index of their reinforcing properties. The second experiment used operant conditioning to reveal the discriminative properties of the different artistic styles of such paintings. Results suggest that the paintings have both discriminative and reinforcing properties for Java sparrows. However, the reinforcing properties vary from individual to individual. This is the first report demonstrating reinforcing properties of visual artworks in non-human animals.     

Second-order conditioning with diffuse auditory reinforcers in the pigeon

Pigeon subjects were used in five experiments investigating second-order conditioning with visual second-order and diffuse auditory first-order stimuli. Experiment 1 used a discriminative conditioning procedure to demonstrate reliable and substantial second-order conditioning with these stimuli. In Experiments 2 and 3, extinction of the auditory first-order stimulus after second-order conditioning had little effect upon responding to the second-order stimulus, when compared to a stimulus whose reinforcer was maintained. Experiment 4 compared directly the susceptibility of second-order responding to extinction of the first-order reinforcing stimulus as a function of the modality of that reinforcer. When a visual second-order stimulus was paired with a visual reinforcer, and the response to the latter was extinguished, then second-order responding was greatly reduced relative to control levels. In contrast, when that reinforcer was an auditory stimulus, second-order responding was not affected by the current value of the first-order stimulus after conditioning. Finally, in Experiment 5 the auditory stimulus was established as a reinforcer through discriminative-operant training. Following second-order conditioning, extinction of responding to this stimulus again had little impact upon responding to the second-order stimulus with which it had been paired. These results are discussed in terms of previous work on second-order conditioning with rat and pigeon subjects.     

Between-person effects on attention and action: Joe and Fred revisited

Previous study indicates that target–target inhibition of return (IOR) is not restricted to a single nervous system. Specifically, watching another person perform a goal-directed aiming movement engages similar inhibitory processes on a subsequent aiming attempt as if having performed the preceding movement oneself. This between-person effect has been attributed to the mirror neuron system. In the study reported here, we replicated this finding and examined the relative importance of automatic stimulus alerting events and action–observation by dissociating these two influences. This was done by having two people alternately perform sets of two aiming trials to the same equally probable targets. Under some experimental conditions, one or both of the performers moved to a non-illuminated target. In this way, we dissociated the stimulus and observed event under some between-person conditions. Although IOR was greatest when the stimulus and observed events were compatible, both contributed to the between-person inhibitory processes slowing the responses (Experiment 1). The impact of observing another person perform an aiming movement appears to have more to do with realizing a particular spatial goal than seeing the biological motion associated with achieving that goal (Experiment 2). Findings that both the illumination of a visual target signal and the observation of another person’s action engage similar attention–action processes are consistent with action-based accounts of visual selective attention.     

The neural basis of mirror symmetry detection: a review

The human visual system is extremely sensitive to the presence of bilateral (mirror) symmetry. In this review, I summarise the results of recent work investigating the neural basis of mirror symmetry detection, focusing in particular on brain stimulation evidence. Overall, available findings converge in pointing to the lateral occipital (LO) complex, especially in the right hemisphere, as a key region causally involved in symmetry detection. Interestingly, they also suggest that another region in the right extrastriate visual cortex, the occipital face area (OFA), is causally implied in symmetry detection, posing an interesting connection at the neural level between visual cortex responses to faces and to symmetry. Finally, this review also considers evidence on haptic symmetry detection in sighted and early blind individuals that points to LO as a multi-modal symmetry-sensitive region, and suggests that symmetry is a salient perceptual feature mediated by LO even when any visual experience is missing.     

Through the looking glass: how the relationship between an object and its reflection affects the perception of distance and size

This is the first study to test the extent to which reflections help locate objects in space and perceive their size. For planar mirrors, the relative size of a target and its reflection is informative about the absolute distance of the target in units of the distance between target and mirror surface. When the target is near the mirror, target and reflection are similar in size; as the target moves away from the mirror, the difference in size increases. Observers saw a pair of objects in front of a mirror and judged relative size and distance (separately). Other visual cues to size and distance were eliminated, except lateral offset, which was tested in experiment 3. Experiment 2 controlled for the presence of directional feedback. Results showed orderly psychophysical functions for both size and distance with steeper slopes for distance judgments. In experiments 4 and 5 stereograms were used. Even when binocular information was present, the additional cue provided by reflections increased the accuracy of size and distance judgments. The same pattern of results was observed in the absence of feedback.     

Collisions between moving visual targets: what controls alternative ways of seeing an ambiguous display?

When identical visual targets move directly toward and then past one another, they appear either to stream past one another or to bounce off each other. Bertenthal et al (1993 Perception 22 193-207) accounted for the relative strengths of these two percepts by invoking a directional bias, arising from cooperative interactions within a network of motion detectors. We tested this explanation by devising conditions that would enhance or diminish the strength of such a directional bias. In separate experiments we varied (i) the presence or absence of temporal transients (pausing, disappearance, occlusion); (ii) the distances travelled by the targets; and (iii) their acceleration or deceleration before and after collision. The tendency to see the objects stream past one another was not related to the strength of an hypothesized directional bias, suggesting that the perception of this ambiguous motion display was not mediated by directional recruitment. Instead, the results suggest that perceived direction reflects the operation of neural constraints that mirror the constraints operating upon moving objects in the three-dimensional natural world.     

Mirror-reading in right- and left-handers

In mirror-reading, words are read from right to left and letters are read in a reverse right-to-left orientation. In one experiment we compared the ability of normal right- and left-handed subjects to mirror-read and found that the left-handers made fewer errors and could read mirror print more rapidly. In a second experiment we attempted to learn whether there is a hemifield superiority for reading mirror words and whether there are any differences between left- and right-handers in a hemifield. We found that although both right- and left-handers more rapidly detected mirror words projected to the left visual half-field, there were no differences between groups. However, in the right visual half-field, the performance of left-handers was superior to that of the right-handers. The results of the hemifield study suggest that left-handers may be superior at reading mirror words because they can more easily reverse their scanning pattern.     

Strange-face illusions during inter-subjective gazing

In normal observers, gazing at one’s own face in the mirror for a few minutes, at a low illumination level, triggers the perception of strange faces, a new visual illusion that has been named ‘strange-face in the mirror’. Individuals see huge distortions of their own faces, but they often see monstrous beings, archetypal faces, faces of relatives and deceased, and animals. In the experiment described here, strange-face illusions were perceived when two individuals, in a dimly lit room, gazed at each other in the face. Inter-subjective gazing compared to mirror-gazing produced a higher number of different strange-faces. Inter-subjective strange-face illusions were always dissociative of the subject’s self and supported moderate feeling of their reality, indicating a temporary lost of self-agency. Unconscious synchronization of event-related responses to illusions was found between members in some pairs. Synchrony of illusions may indicate that unconscious response–coordination is caused by the illusion–conjunction of crossed dissociative strange-faces, which are perceived as projections into each other’s visual face of reciprocal embodied representations within the pair. Inter-subjective strange-face illusions may be explained by the subject’s embodied representations (somaesthetic, kinaesthetic and motor facial pattern) and the other’s visual face binding. Unconscious facial mimicry may promote inter-subjective illusion–conjunction, then unconscious joint-action and response–coordination.     

Some motivational properties of sensory stimulation in psychotic children

The purpose of this experiment was to assess the reinforcing properties of sensory stimulation for autistic children. Three different types of sensory stimulation were used: music, visual flickering stimulation (e.g., strobe light), and visual movement (e.g., windshield wiper). In a given session, one of the three kinds of sensory stimulation was presented for 5 sec contingent upon the children's bar pressing (FR5). In Phase I, which was designed to assess the differential reinforcement value of these events, four children participated in sessions with each of the sensory events. In Phase II, designed to assess variables influencing the maintenance of responding for the sensory events, two children continued to participate in sessions with their preferred sensory event until satiation occurred. The results showed the following: (1) Sensory events could be used as reinforcing stimuli to produce a high rate of responding which was relatively durable over time: (2) the reinforcement function of the sensory events was idiosyncratic across children. with one child preferring one kind of sensory event, and another child preferring a different kind; (3) there was substantial variability in daily response rates: and (4) when a child satiated on a particular sensory event, a relatively small change in the sensory event was sufficient to recover a high rate of responding. The results of this study suggest that sensory reinforcers can profitably be used in behavior therapy with autistic children.     

VOLITION: A NEW EXPERIMENTAL APPROACH

The subjects were presented with a drawing task, i.e. to follow a straight line. Later, without the subjects' knowledge, the experimenter inserted a mirror so that the subjects were looking at another person's hand in a mirror, placed so that the subjects still thought they were looking at their own hands. When both the subjects' and the stooge's hand were following the straight line, the subjects experienced the alien hand as their own and that its movements were controlled by themselves (voluntary movements). When the stooge drew a curve to the right, the subjects still experienced the hand as their own, but now making involuntary movements. Thus, 'the visual hand' dominated 'the kinesthetical hand' despite the fact that the subjects objectively made compensatory movements to the left.     

Distinctiveness and the recognition mirror effect: evidence for an item-based criterion placement heuristic

Superior detection and rejection of 1 versus another class of items during recognition is called the mirror effect. Some mirror effects may involve strategic criterion adjustments based on item distinctiveness and its relation to memorability. Three experiments demonstrated mirror effects for known versus unknown scenes and 1 suggested a similar pattern for faces. In opposition to preexperimental familiarity, lures from known and frequently encountered locations were confidently rejected more often than unknown lures. Forgetting and speeding recognition reversed this lure response pattern, suggesting abandonment of strategic adjustment in favor of a single fixed criterion. With sufficient response time and recent encoding, observers demand more evidence for conceptually distinctive items, perhaps because such items typically foster vivid recollection during retrieval.     

Semantic interference from visual object recognition on visual imagery

A new technique for examining the interaction between visual object recognition and visual imagery is reported. The "image-picture interference" paradigm requires participants to generate and make a response to a mental image of a previously memorized object, while ignoring a simultaneously presented picture distractor. Responses in 2 imagery tasks (making left-right higher spatial judgments and making taller-wider judgments) were longer when the simultaneous picture distractor was categorically related to the target distractor relative to unrelated and neutral target-distractor combinations. In contrast, performance was not influenced in this way when the distractor was a related word, when a semantic categorization decision was made to the target, or when distractor and target were visually but not categorically related to one another. The authors discuss these findings in terms of the semantic representations shared by visual object recognition and visual imagery that mediate performance.     

Male versus female Siamese fighting fish as reinforcing stimuli for conspecific males in single- and two-choice operant situations

Two experiments attempted to determine the reinforcing effectiveness of visual exposure to a female versus a male stimulus in male Siamese fighting fish (Betta splendens). This was accomplished by making male or female presentation contingent upon an operant ring swimming response in single- (Experiment 1) and two-choice (Experiment 2) continuous reinforcement operant situations for 1 hr per day. It was found that visual exposure to a female stimulus was behaviorally reinforcing in a way comparable to that typically found in intermale studies. If given a choice, male test subjects were observed to demonstrate a consistent preference for the female as opposed to the male stimulus. The results are discussed in terms of stimulus discrimination and approach-avoidance conflict as differentially elicited by male and female target stimuli.     

Observation and physical practice: Coding of simple motor sequences

An experiment was conducted to determine the coordinate system used in the development of movement codes during observation and utilized on later physical practice performance of a simple spatial–temporal movement sequence. The task was to reproduce a 1.3-s spatial–temporal pattern of elbow flexions and extensions. An intermanual transfer paradigm with a retention test and two transfer tests was used: a mirror transfer test where the same pattern of muscle activation and limb joint angles was required and a nonmirror transfer test where the visual–spatial pattern of the sequence was reinstated on the transfer test. The results indicated a strong advantage for participants in the physical practice condition when transferred to the mirror condition in which the motor coordinates (e.g., pattern of muscle activation and joint angles) were reinstated relative to transfer performance when the visual–spatial coordinates were reinstated (visual and spatial location of the target waveform). The observation group, however, demonstrated an advantage when the visual–spatial coordinates were reinstated. These results demonstrate that codes based in motor coordinates can be developed relatively quickly for simple rapid movement sequences when participants are provided physical practice, but observational practice limits the system to the development of codes based in visual–spatial coordinates. Performances of control participants, who were not permitted to practise or observe the task, were quite poor on all tests.     

Visual reinforcement in the female Siamese fighting fish, Betta splendens

Operant conditioning with Betta splendens (Bettas) has been investigated extensively using males of the species. Ethological studies of female Bettas have revealed aggressive interactions that qualitatively parallel those between male Bettas. Given these similarities, four experiments were conducted with female Bettas to examine the generality of a widely reported finding with males: mirror-image reinforcement. Swimming through a ring was reinforced by a 10-s mirror presentation. As with males, ring swimming was acquired and maintained when mirror presentations were immediate (Experiments 1, 2, and 3) and delayed (Experiment 4). The failure of conventional extinction (Experiments 1 and 2) and response-independent mirror presentations (Experiment 3) to maintain responding confirmed the reinforcing properties of mirror presentation. These results extend previous findings of mirror images as reinforcers in males of the same species and illustrate a complementarity between behavioral ecology and the experimental analysis of behavior.     

The efficacy of auditory and visual conjugate reinforcers in infant conditioning

The effectiveness of the separate auditory and visual components of a combined auditory-visual conjugate reinforcer was assessed in 273-month-old infants. All conditions of contingent reinforcement were equally effective in promoting acquisition, but only the removal of the singly presented auditory component resulted in significant response diminution. Although noncontingent stimulation in all conditions was ineffective in altering operant footkicks, it did sustain visual attention at a high level equivalent to that produced by contingent stimulation over the major portion of acquisition. The results were discussed in terms of the reinforcing properties of varied stimulation.     

Comparing stimulus preference and response force in a conjugate preparation

Researchers used a conjugate preparation to evaluate how response force changed based on participants' preferences for visual stimuli. First, researchers used a verbal preference assessment to evaluate each participant's preference for viewing for five object categories of visual stimuli; this process identified high preference (HP) stimuli and low preference stimuli for most participants. Thereafter, researchers exposed each participant to the five stimulus categories in a randomized order while using a force dynamometer to measure their response force to increase visual clarity of each stimulus. Results indicate the majority of participants' HP stimuli corresponded to the stimulus category for which they exerted the highest mean force. These preliminary findings suggest conjugate preparations involving response force may provide another option for measuring the relative value of some stimulus events.