Perception

Franklin et al (1993, Leonardo 26 103–108) reported that title information influenced the interpretation of paintings but not the way observers explore and look at the paintings; in their study subjects used a hand pointer to indicate where they looked. We used eye-movement recording and examined the effect of title on eye-movement exploration of nonrealistic cubist paintings giving rise to free interpretation. Three paintings by Fernand Léger were used: The Wedding contained high density of small fragments of real human faces, limbs, or arbitrary fragments mixed with large plane surfaces; The Alarm Clock consisted of arbitrary fragments creating perception of a person; Contrast of Forms contained forms and cylinders. Different groups of naive subjects explored paintings without knowing the title (spontaneous condition), with the instruction to invent a title (active condition), and after announcement of the authentic title (driven condition). Exploration time was unrestricted and eye movements were recorded by Chronos video-oculography.

Fixation duration was found to increase in the driven condition relative to active condition; such increase occurred for all paintings. In contrast, fixation-duration variability remained stable over all title conditions. Saccade amplitude increased in the driven condition for Contrast of Forms. Increase of fixation duration and of saccade size are attributed to additional cognitive analysis, ie search fitting between the title and the painting. When comparing paintings within each title condition, The Wedding produced different results than the other paintings: longer exploration time (in spontaneous condition), higher fixation duration variability (in spontaneous and driven conditions), but smaller saccade sizes (in active and driven conditions). The differences are attributed to visual aspects (high density of small fragments) but also to complex semantic analysis of multiple segments of faces and limbs contained by this painting.

Spatial distribution of fixation time was highly selective, with a preponderance of the central area that was the most fixated for all paintings and all title conditions. In the driven condition, however, loci of most frequent fixations were different than in the other conditions from the first 5 s; particularly for The Alarm Clock the title drove the eyes rapidly on the inconspicuous fragment of the clock. Our findings go against Franklin's conclusions. We conclude that title information influences both physiological parameters of eye movements and the distribution of fixation time over different selected areas of the painting.

Ever since Kepler described the image-forming properties of the eye (400 years ago) there has been a widespread belief, which remains to this day, that an object seen with one eye is always seen where it is. Predictions made by Ptolemy in the first century, Alhazen in the eleventh, and Wells in the eighteenth, and supported by Towne, Hering, and LeConte in the nineteenth century, however, are contrary to this claimed veridicality. We discuss how among eighteenth-and nineteenth-century British researchers, particularly Porterfield, Brewster, and Wheatstone, the erroneous idea continued and also why observations made by Wells were neither understood nor appreciated. Finally, we discuss recent data, obtained with a new method, that further support Wells's predictions and which show that a distinction between headcentric and relative direction tasks is needed to appreciate the predictions.

Anomalous motion illusions represent a popular class of illusions and several studies have made an effort to explain their perception. However, understanding is still inconsistent. Age-related differences in susceptibility to illusory motion may contribute to further clarification of the underlying processing mechanisms. We investigated the effect of age on the perception of four different anomalous motion illusions. The Enigma illusion, the Rotating-Snakes illusion, the Pinna illusion, and the Rotating-Tilted-Lines illusion were tested on a total of one hundred and thirty-nine participants covering an age range from 3 to 82 years. In comparison with young adults, children showed a lower likelihood of perceiving motion in all illusions with the exception of the Rotating-Tilted-Lines illusion. For adult subjects, we found significant age effects in the Rotating-Snakes illusion and the Rotating-Tilted-Lines illusion: occurrence of the illusory effect decreased with age. The other two illusions turned out to be unaffected by aging. Finally, inter-correlations between different motion illusions revealed that only the Pinna illusion and the Rotating-Tilted-Lines illusion correlated significantly with each other. The results confirm that anomalous motion illusions should not be considered as a homogeneous group. Possible links between perceptual data and neurophysiological changes related to age are discussed. Perceptual differences due to age provide the opportunity to improve our understanding of illusory motion and point to specific underlying mechanisms.

Biological-motion perception consists of a number of different phenomena. They include global mechanisms that support the retrieval of the coherent shape of a walker, but also mechanisms which derive information from the local motion of its parts about facing direction and animacy, independent of the particular shape of the display. A large body of the literature on biological-motion perception is based on a synthetic stimulus generated by an algorithm published by James Cutting in 1978 (Perception 7 393–405). Here we show that this particular stimulus lacks a visual invariant inherent to the local motion of the feet of a natural walker, which in more realistic motion patterns indicates the facing direction of a walker independent of its shape. Comparing Cutting's walker to a walker derived from motion-captured data of real human walkers, we find no difference between the two displays in a detection task designed such that observers had to rely on global shape. In a direction discrimination task, however, in which only local motion was accessible to the observer, performance on Cutting's walker was at chance, while direction could still be retrieved from the stimuli derived from the real walker.

Visual recognition of three-dimensional (3-D) objects is relatively impaired for some particular views, called accidental views. For most familiar objects, the front and top views are considered to be accidental views. Previous studies have shown that foreshortening of the axes of elongation of objects in these views impairs recognition, but the influence of other possible factors is largely unknown. Using familiar objects without a salient axis of elongation, we found that a foreshortened symmetry plane of the object and low familiarity of the viewpoint accounted for the relatively worse recognition for front views and top views, independently of the effect of a foreshortened axis of elongation. We found no evidence that foreshortened front–back axes impaired recognition in front views. These results suggest that the viewpoint dependence of familiar object recognition is not a unitary phenomenon. The possible role of symmetry (either 2-D or 3-D) in familiar object recognition is also discussed.

Faces and self-referential material (eg one's own name) are more likely to capture attention in the inattentional-blindness (IB) paradigm than other stimuli. This effect is presumably due to the meaning of these stimuli rather than to their familiarity [Mack and Rock, 1998 Inattentional Blindness (Cambridge, MA: MIT Press)]. In previous work, IB has been investigated mostly with schematic stimuli. In the present study, the generalisability of this finding was tested with photographic stimuli. In support of the view that faces constitute a special category of stimuli, pictures of faces were found to resist more to IB than pictures of common objects (experiment 1) or than pictures of inverted faces (experiment 2). In a third experiment, the influence of face familiarity and identity (the participant's own face, a friend's face, and an unknown face) on IB rates was evaluated. Unexpectedly, no differential resistence to blindness across these three kinds of faces was found. In conclusion, pictures of faces attracted attention more than pictures of objects or inverted faces in the IB paradigm. However, this effect was not dependent on face familiarity or identity.

Human faces under natural illumination, and human eyes in their unique morphology, include specific contrast polarity relations that face-detection mechanisms could capitalise on. Newborns have been shown to preferentially orient to simple face-like patterns only when they contain face- or gaze-relevant contrast. We investigated whether human adults show similar preferential orienting towards schematic face-like stimuli, and whether this effect depends on the contrast polarity of the stimuli. In two experiments we demonstrate that upright schematic face-like patterns elicit faster eye movements in adult humans than inverted ones, and that this occurs only if they contain face- or gaze-relevant contrast information in the whole stimulus or in the eye region only. These results suggest that primitive mechanisms underlying the orienting bias towards faces and eyes influence and modulate social cognition not just in infants but in adults as well.

The ability of fish to perceive subjective (or illusory) contours, ie contours that lack a physical counterpart in terms of luminance contrast gradients, was investigated. In the first experiment, redtail splitfins (Xenotoca eiseni), family Goodeidae, were trained to discriminate between a geometric figure (a triangle or a square) on various backgrounds and a background without any figure. Thereafter, the fish performed test trials in which illusory squares or triangles were obtained by (i) interruptions of a background of diagonal lines, (ii) phase-shifting of a background of diagonal lines, and (iii) pacmen spatially arranged to induce perception of Kanizsa subjective surfaces. In all three conditions, fish seemed to generalise their responses to stimuli perceived as subjective contours by humans. Fish chose, correctly, squares or triangles made of interrupted or phase-shifted diagonal lines from uniform backgrounds of diagonal lines, as well as illusory square or triangle Kanizsa figures from figures in which the inducing pacmen were scrambled. In the second experiment, fish were trained to discriminate between a vertical and a horizontal bar with luminance contrast gradients, and then tested with vertically and horizontally oriented illusory bars, created either through interruption or spatial phase-shift of inducing diagonal lines. Fish appeared to be able to generalise the orientation discrimination to illusory contours. These results demonstrate that redtail splitfins are capable of perceiving illusory contours.

SE, a 19-year-old female college student and a color–grapheme synesthete, reported consistent synesthetic experiences (photisms) for digits, and most letters in the Roman and Hebrew alphabets over a 6-month period. Photisms for later-learned Hebrew letters were influenced by those of the Roman alphabet and photisms for auditorily presented words were influenced by the spelling of the words. As hypothesized, in two studies, SE's solution times for addition problems were significantly slower when the colors of the digits in the problems mismatched her synesthetic photisms than when they matched or were in black (p < 0.001), whereas color had no effect on solution times for six female non-synesthetes (aged 19 to 22 years). Implications for learning and cognitive processing are discussed.

It has been hypothesized (Lederman et al, 1990 Perception & Psychophysics 47 54–64) that sighted people adopt a visual translation process when attempting to identify 2-D raised images by touch—they employ a visual image as a mediator between haptic sensory information and the object representation. If this hypothesis is correct, the performance in identifying pictures by touch (with eyes closed) ought to be better when the head is facing the picture than when facing in a very different direction. In this study, thirty-six blindfolded participants were required to identify raised pictures of common objects with their head facing either in the same direction as the raised picture or in an orthogonal direction. Identification performance was measured in terms of accuracy and response latencies. Overall, participants were more accurate and faster when their heads faced in the same direction as the picture. This finding is discussed in terms of spatial congruency between haptic representations of pictures and visual (or spatial) imagery created during exploration of haptic pictures.

Johansson (1973 Perception & Psychophysics 14 201–211) suggested that point-light displays that are static—so-called ‘snapshots’—contain little or no information about the actor or their action. Here we present data that suggest even naive observers can perceive such information from static point-light arrays. Observers were able, at rates better than chance, to discriminate the directions of facing of sagittally viewed static point-light walkers. The data show also that, without feedback, performances improved with experience. Our data have implications for assumptions made in designing experiments with point-light displays and for models of the neural mechanisms mediating biological motion perceptions.

We provide preliminary evidence that listening to music through headphones alters the perception of space around the body—specifically, the interpersonal distance maintained between the self and others. In comparison to an external auditory environment, wearing headphones or earplugs increased the amount of space maintained between the wearer and another person during an active approach paradigm. This finding suggests that, when external cues to spatial location (such as sound) are removed, people compensate by increasing the distance between themselves and others. The implications of this research for navigating busy urban environments and for the social interactions of wearers of personal music systems are discussed.