Lightness compression and hue changes

Two experiments were performed to relate the Bezold-Brücke (B-B) and lightness compression effects. The first used a calibrated screen to present an achromatic luminance staircase. In addition, it reproduced, the methodology and the essential aspects the lightness compression effect discovered by Cataliotti and Gilchrist (1995). That is, observers perceived a truncated grey scale (from white to medium grey) when the staircase was the only stimulation in the near background (Gelb condition), but not when presented on a Mondrian background, because of the high articulation level provided by this background. Experiment 1 design also included two other backgrounds that produced a partial compression effect. In Experiment 2, two chromatic staircases were used. Employing a naming task, changes in hue perception were only observed for the susceptible staircase. The observed changes were of two types. First, for the full staircase presentations, a Gelb background produced maximum lightness compression (more similarity in the lightness of the staircase stimuli) and, also, a minimum B-B effect (fewer differences in hue). Second, only for the Gelb condition, there were changes in the hue of the lowest luminance staircase stimuli depending on the staircase extension. Results are discussed in the framework of the anchoring theory of lightness perception.     

Surface lightness influences perceived room height

Surprisingly little scientific research has been conducted on the effects of colour and lightness on the perception of spaciousness. Practitioners and architects typically suggest that a room's ceiling appears higher when it is painted lighter than the walls, while darker ceilings appear lower. Employing a virtual reality setting, we studied the effects of the lightness of different room surfaces on perceived height in two psychophysical experiments. Observers judged the height of rooms varying in physical height as well as in the lightness of ceiling, floor, and walls. Experiment 1 showed the expected increase of perceived height with increases in ceiling lightness. Unexpectedly, the perceived height additionally increased with wall lightness, and the effects of wall lightness and ceiling lightness were roughly additive, incompatible with a simple effect of the lightness contrast between the ceiling and the walls. Experiment 2 demonstrated that the floor lightness has no significant effect on perceived height, and that the total brightness of the room is not the critical factor influencing the perceived height. Neither can the results be explained by previously reported effects of brightness on apparent depth or perceived distance.     

Investigating the contribution of metacontrast to the Fröhlich effect for size

According to the Fr?hlich effect, observers perceive the initial position of a fast moving stimulus displaced in the direction of motion. On the basis of Kirschfeld and Kammer's as well as Fr?hlich's original assumption that metacontrast plays an important role in the emergence of the phenomenon, we predicted different amounts of misperception for stimulus enlargement compared to stimulus reduction. These basic predictions were confirmed in Experiment 1. In Experiment 2, we investigated whether an overestimation-bias might account for these results. But the overestimation of non-changing stimuli was too small to adequately explain the dissociation. In Experiment 3, we predicted and found different effects of the factor stimulus lightness on misperception in the enlargement and reduction condition. In Experiment 4, we showed that misperception in the enlargement condition is reduced when frames are used instead of filled stimuli, as in the earlier experiments. Results are discussed with respect to the original Fr?hlich effect.     

Photometric, geometric, and perceptual factors in illumination-independent lightness constancy

It has been shown that lightness constancy depends on the articulation of the visual field (Agostini & Galmonte, 1999). However, among researchers there is little agreement about the meaning of "articulation." Beyond the terminological heterogeneity, an important issue remains: What factors are relevant for the stability of surface color perception? Using stimuli with two fields of illumination, we explore this issue in three experiments. In Experiment 1, we manipulated the number of luminances, the number of reflectances, and the number of surfaces and their spatial relationships; in Experiment 2, we manipulated the luminance range; finally, in Experiment 3 we varied the number of surfaces crossed by the illumination edge. We found that there are two relevant factors in optimizing lightness constancy: (1) the lowest luminance in shadow and (2) the co-presence of patches of equal reflectance in both fields of illumination. The latter effect is larger if these patches strongly belong to each other. We interpret these findings within the albedo hypothesis.     

Cross-domain Repetition Priming in Person Recognition

Three experiments examining repetition priming of personal names are reported. In each experiment, faces are used as prime stimuli and people's names as the test stimuli. Experiment 1 fails to demonstrate priming from faces to names when the same task-a familiar/ unfamiliar judgement-is made in prime and test phases. Experiment 2 shows that priming is observed when the same semantic judgement (British/ American) is made in prime and test phases. Experiment 3 shows that priming is observed when different semantic judgements (dead/ alive, British/ American) are made at prime and test phase. These results suggest that transfer appropriate processing cannot provide the sole account of repetition priming in person recognition. Instead, the results are interpreted in terms of a structural account of priming, embedded within an interactive activation and competition model of person recognition.     

Effect of contrast level and temporal order on the Ebbinghaus circles illusion

Forty-eight undergraduates between 17 and 24 years of age judged the size of the central circle in Ebbinghaus figures presented under either simultaneous or successive viewing conditions. Successive presentation diminished the magnitude of illusion produced by the underestimated Ebbinghaus figure and totally eliminated the illusion normally produced by the overestimated figure. Variations in lightness contrast of the central and surrounding circles significantly altered the magnitude of illusion produced by both simultaneous Ebbinghaus figures as well as that produced by the successive underestimated figure. These data suggest the presence of a contour interaction process in both simultaneous Ebbinghaus illusions.     

A reversed Ebbinghaus–Titchener illusion in bantams (Gallus gallus domesticus)

A disk surrounded by smaller disks looks larger, and one surrounded by larger disks looks smaller than reality. This visual illusion, called the Ebbinghaus–Titchener illusion, remains one of the strongest and most robust illusions induced by contrast with the surrounding stimuli in humans. In the present study, we asked whether bantams would perceive this illusion. We trained three bantams to classify six diameters of target disks surrounded by inducer disks of a constant diameter into “small” or “large”. In the test that followed, the diameters of the inducer disks were systematically changed. The results showed that the Ebbinghaus–Titchener figures also induce a strong illusion in bantams, but in the other direction, that is, bantams perceive a target disk surrounded by smaller disks to be smaller than it really is and vice versa. Possible confounding factors, such as the gap between target disk and inducer disks and the weighted sum of surface of these figural elements, could not account for the subjects’ biased responses. Taken together with the pigeon study by Nakamura et al. (J Exp Psychol Anim Behav Process 34:375–387 2008), these results show that bantams as well as pigeons perceive an illusion induced by assimilation effects, not by contrast ones, for the Ebbinghaus–Titchener types of illusory figures. Perhaps perceptual processes underlying such illusory perception (i.e., lack of contrast effects) shown in bantams and pigeons may be partly shared among other avian species.     

Perception of the Ebbinghaus illusion in four-day-old domestic chicks (Gallus gallus)

In the Ebbinghaus size illusion, a central circle surrounded by small circles (inducers) appears bigger than an identical one surrounded by large inducers. Previous studies have failed to demonstrate sensitivity to this illusion in pigeons and baboons, leading to the conclusion that avian species (possibly also nonhuman primates) might lack the neural substrate necessary to perceive the Ebbinghaus illusion in a human-like fashion. Such a substrate may have been only recently evolved in the primate lineage. Here, we show that this illusion is perceived by 4-day-old domestic chicks. During rearing, chicks learnt, according to an observational-learning paradigm, to find food in proximity either of a big or of a small circle. Subjects were then tested with Ebbinghaus stimuli: two identical circles, one surrounded by larger and the other by smaller inducers. The percentage of approaches to the perceptually bigger target in animals reinforced on the bigger circle (and vice versa for the other group) was computed. Over four experiments, we demonstrated that chicks are reliably affected by the illusory display. Subjects reinforced on the small target choose the configuration with big inducers, in which the central target appears perceptually smaller; the opposite is true for subjects reinforced on the big target. This result has important implications for the evolutionary history of the neural substrate involved in the perception of the Ebbinghaus illusion.     

Computation of mean size is based on perceived size

The present study investigated whether computation of mean object size was based on perceived or physical size. The Ebbinghaus illusion was used to make the perceived size of a circle different from its physical size. Four Ebbinghaus configurations were presented either simultaneously (Experiment 1) or sequentially (Experiment 2) to each visual field, and participants were instructed to attend only to the central circles of each configuration. Participants’ judgments of mean central circle size were influenced by the Ebbinghaus illusion. In addition, the Ebbinghaus illusion influenced the coding of individual size rather than the averaging. These results suggest that perceived rather than physical size was used in computing the mean size.     

Planning to reach for an object changes how the reacher perceives it

Three experiments assessed the influence of the Ebbinghaus illusion on size judgments that preceded verbal, grasp, or touch responses. Prior studies have found reduced effects of the illusion for the grip-scaling component of grasping, and these findings are commonly interpreted as evidence that different visual systems are employed for perceptual judgment and visually guided action. In the current experiments, the magnitude of the illusion was reduced by comparable amounts for grasping and for judgments that preceded grasping (Experiment 1). A similar effect was obtained prior to reaching to touch the targets (Experiment 2). The effect on verbal responses was apparent even when participants were simply instructed that a target touch task would follow the verbal task. After participants had completed a grasping task, the reduction in the magnitude of the illusion remained for a subsequent verbal-response judgment task (Experiment 3). Overall, the studies demonstrate strong connections between action planning and perception.     

Perceptual processing of adjacent and nonadjacent tactile nontargets.

Previous research has shown that subjects appear unable to restrict processing to a single finger and ignore a stimulus presented to an adjacent finger. Furthermore, the evidence suggests that, at least for moving stimuli, an adjacent nontarget is fully processed to the level of incipient response activation. The present study replicated and expanded upon these original findings. The results of Experiment 1 showed that an equally large response-competition effect occurred when the nontarget was presented to adjacent and nonadjacent fingers (on the same hand). The results of Experiment 2 showed that the effects observed in Experiment 1 (and in previous studies) were also obtained with stationary stimuli. Although small, there was some indication in the results of Experiment 2 that interference may dissipate more rapidly with distance with stationary stimuli. An additional finding was that interference effects were observed in both experiments with temporal separations between the target and nontarget of up to 100 msec. In Experiment 3, target and nontarget stimuli were presented to opposite hands. Although reduced, interference was still evident with target and nontarget stimuli presented to opposite hands. Varying the physical distance between hands did not produce any change in the amount of interference. The results suggest that the focus of attention on the skin extends nearly undiminished across the fingers of one hand and is not dependent upon the physical distance between sites of stimulation.     

Perceptual processing of adjacent and nonadjacent tactile nontargets

Previous research has shown that subjects appear unable to restrict processing to a single finger and ignore a stimulus presented to an adjacent finger. Furthermore, the evidence suggests that, at least for moving stimuli, an adjacent nontarget is fully processed to the level of incipient response activation. The present study replicated and expanded upon these original findings. The results of Experiment 1 showed that an equally large response-competition effect occurred when the nontarget was presented to adjacent and nonadjacent fingers4on the same hand). The results of Experiment 2 showed that the effects observed in Experiment 1 (and in previous studies) were also obtained with stationary stimuli. Although small, there was some indication in the results of Experiment 2 that interference may dissipate more rapidly with distance with stationary stimuli. An additional finding was that interference effects were observed in both experiments with temporal separations between the target and nontarget of up to 100 msec. In Experiment 3, target and nontarget stimuli were presented to opposite hands. Although reduced, interference was still evident with target and nontarget stimuli presented to opposite hands. Varying the physical distance between hands did not produce any change in the amount of interference. The results suggest that the focus of attention on the skin extends nearly undiminished across the fingers of one hand and is not dependent upon the physical distance between sites of stimulation.     

Dividing attention between auditory and visual perception

To what extent is simultaneous visual and auditory perception subject to capacity limitations and attentional control? Two experiments addressed this question by asking observers to recognize test tones and test letters under selective and divided attention. In Experiment 1, both stimuli occurred on each trial, but subjects were cued in advance to process just one or both of the stimuli. In Experiment 2, subjects processed one stimulus and then the other or processed both stimuli simultaneously. Processing time was controlled using a backward recognition masking task. A significant, but small, attention effect was found in both experiments. The present positive results weaken the interpretation that previous attentional effects were due to the particular duration judgment task that was employed. The answer to the question addressed by the experiments appears to be that the degree of capacity limitations and attentional control during visual and auditory perception is small but significant.     

The role of head-centric spatial reference with a static and kinetic visual disturbance

A static or kinetic visual disturbance affects subjects’ ability to estimate the direction of the gravitational vertical. This kind of error is increased by a head roll inclination. In two experiments, we combined head orientation with a static (Experiment 1: tilted frame) versus kinetic (Experiment 2: rotating disk) visual disturbance. The results showed that with a static visual disturbance, the increase of errors in the inclined head condition was mainly the consequence of a postural head effect like an Aubert effect. On the contrary, with a kinetic visual disturbance, it appears that the disk effect increases with head inclination. However, individual errors observed with the head inclined in front of a stationary disk were systematically correlated with the errors triggered by the same head inclination in front of a rotating disk. These observations confirm that the head axis spatial reference plays an important role in orientation perception, whatever the head position and the kind of visual display.     

Response facilitation and inhibition in manual, vocal, and oculomotor performance: evidence for a modality-unspecific mechanism

In 2 experiments (N = 10, Experiment 1; N = 16, Experiment 2), the authors investigated whether evidence for response facilitation and subsequent inhibition elicited by masked prime stimuli can be observed for output modalities other than manual responding. Masked primes were followed by target stimuli that required a 2-choice manual, saccadic, or vocal response. Performance was measured for compatible trials in which primes and targets were identical and for incompatible trials in which they were mapped to opposite responses. When primes were presented centrally, performance benefits were obtained for incompatible trials; whereas for peripherally presented primes, performance benefits were found in compatible trials. That pattern of results was obtained for manual responses and for saccadic eye movements (Experiment 1), demonstrating that those effects are not mediated by specialized dorsal pathways involved in visuomanual control. An analogous pattern of effects was found when manual and vocal responses were compared (Experiment 2). Because vocal responding is controlled by the inferotemporal cortex, that result shows that prime-target compatibility effects are not primarily mediated by the dorsal stream, but appear to reflect modality-unspecific visuomotor links that allow rapid activation of motor responses that may later be subject to inhibition.     

When hearing turns into playing: Movement induction by auditory stimuli in pianists

In this study, pianists were tested for learned associations between actions (movements on the piano) and their perceivable sensory effects (piano tones). Actions were examined that required the playing of two-tone sequences (intervals) in a four-choice paradigm. In Experiment 1, the intervals to be played were denoted by visual note stimuli. Concurrently with these imperative stimuli, task-irrelevant auditory distractor intervals were presented (“potential” action effects, congruent or incongruent). In Experiment 2, imperative stimuli were coloured squares, in order to exclude possible influences of spatial relationships of notes, responses, and auditory stimuli. In both experiments responses in the incongruent conditions were slower than those in the congruent conditions. Also, heard intervals actually “induced” false responses. The reaction time effects were more pronounced in Experiment 2. In nonmusicians (Experiment 3), no evidence for interference could be observed. Thus, our results show that in expert pianists potential action effects are able to induce corresponding actions, which demonstrates the existence of acquired action-effect associations in pianists.     

The roles of inducer size and distance in the Ebbinghaus illusion (Titchener circles)

Although the Ebbinghaus illusion is commonly used as an example of a simple size-contrast effect, previous studies have emphasised its complexity by identifying many factors that potentially influence the magnitude of the illusion. Here, in a series of three experiments, we attempt to simplify this complexity. In each trial, subjects saw a display comprising, on one side, a target stimulus surrounded by inducers and, on the other, an isolated probe stimulus. Their task was to indicate whether the probe appeared larger or smaller than the target. Probe size was adjusted with a one-up, one-down staircase procedure to find the point of subjective equality between probe and target. From these experiments, we argue that the apparent effects of inducer size are often confounded by the relative completeness of the inducing surround and that factors such as the similarity of the inducers and target are secondary. We suggest a simple model that can explain most of the data in terms of just two primary and independent factors: the relative size of the inducers and target, and the distance between the inducers and the target. The balance between these two factors determines whether the size of the target is underestimated or overestimated.     

Perception of the Ebbinghaus illusion in 5- to 8-month-old infants

The Ebbinghaus illusion is a geometric illusion based on a size-contrast between a central circle and surrounding circles. A central circle surrounded by small inducing circles is perceived as being larger than a central circle surrounded by large inducing circles. In the present study we investigated 5- to 8-month-old infants' perception of the Ebbinghaus illusion using a preferential-looking paradigm. We measured the preference between a central circle surrounded by small inducing circles (overestimated figure) and a central circle surrounded by large inducing circles (underestimated figure). Infants showed a significant preference for the overestimated figure when the central circle was flashing, but not when it was static. Furthermore, there was no preference between the two figures when the central circles were removed. These results suggest that infants' preference reflects their perception of the size illusion of the central circle. There is a possibility that 5- to 8-month-old infants perceive the Ebbinghaus illusion.     

Effect of post-encoding emotion on recollection and familiarity for pictures

Although prior studies have examined the effect of post-encoding emotional arousal on recognition memory for words, it is unknown whether the enhancement effect observed on words generalizes to pictures. Furthermore, prior studies using words have showed that the effect of emotional arousal can be modulated by stimuli valence and delay in emotion induction, but it is unclear whether such modulation can extend to pictures and whether other factors such as encoding method (incidental vs. intentional encoding) can be modulatory. Five experiments were conducted to answer these questions. In Experiment 1, participants encoded a list of neutral and negative pictures and then watched a 3-min neutral or negative video. The delayed test showed that negative arousal impaired recollection regardless of picture valence but had no effect on familiarity. Experiment 2 replicated the above findings. Experiment 3 was similar to Experiment 1 except that participants watched a 3-min neutral, negative, or positive video and conducted free recall before the recognition test. Unlike the prior two experiments, the impairment effect of negative arousal disappeared. Experiment 4, where the free recall task was eliminated, replicated the results from Experiment 3. Experiment 5 replicated Experiments 1 and 2 and further showed that the impairment effects of negative arousal could be modulated by delay in emotion induction but not by encoding method or stimuli valence. Taken together, the current study suggests that the enhancement effect observed on words may not generalize to pictures.     

Priming of emotion recognition

Four experiments investigated priming of emotion recognition using a range of emotional stimuli, including facial expressions, words, pictures, and nonverbal sounds. In each experiment, a prime-target paradigm was used with related, neutral, and unrelated pairs. In Experiment 1, facial expression primes preceded word targets in an emotion classification task. A pattern of priming of emotional word targets by related primes with no inhibition of unrelated primes was found. Experiment 2 reversed these primes and targets and found the same pattern of results, demonstrating bidirectional priming between facial expressions and words. Experiment 2 also found priming of facial expression targets by picture primes. Experiment 3 demonstrated that priming occurs not just between pairs of stimuli that have a high co-occurrence in the environment (for example, nonverbal sounds and facial expressions), but with stimuli that co-occur less frequently and are linked mainly by their emotional category (for example, nonverbal sounds and printed words). This shows the importance of the prime and target sharing a common emotional category, rather than their previous co-occurrence. Experiment 4 extended the findings by showing that there are category-based effects as well as valence effects in emotional priming, supporting a categorical view of emotion recognition.