Stability and change in a perspective reversal illusion

A phenomenologieal explanation is presented for the stability and instability of the appearance of the form of objects as a consequence of changes in (1) the spatial position of the observer with respect to the object, and (2) the amount of time the object is observed from a specific spatial position. In support of the explanation, an object was constructed so that it would have multiple appearances when observed continuously from the same viewpoint. The initial appearance of this object when observed from different spatial positions and the constancy over time of these appearances were demonstrated to be in agreement with the theoretical expectations.     

Sighting-down and the Poggendorff illusion: a mystery within a mystery.

As reported before, sighting-down one of the diagonal lines on a typical Poggendorff pattern will reduce the illusion even if that situation is only pictorial. But here it is also argued that sighting-down itself requires further understanding.     

The peripheral drift illusion: a motion illusion in the visual periphery

Circularly repeating patches containing sawtooth luminance gradients produce a sensation of motion when viewed in the periphery. Illusory motion is perceived in a dark-to-light direction, but only when one's gaze is directed to different locations around the stimulus, a point outside the display is fixated and the observer blinks, or when the stimulus is sequentially displayed at different locations whilst the observer fixates one point. We propose that the illusion is produced by the interaction of three factors: (i) introducing transients as a result of eye movements or blinks; (ii) differing latencies in the processing of luminance; and (iii) spatiotemporal integration of the differing luminance signals in the periphery.     

Psychotherapy training in a changing world: A Swedish perspective

The City and Hackney Primary Care Psychotherapy Consultation Service is an innovative, public sector service designed to support GPs in meeting the needs of patients with complex psychological/physical health issues throughout the London Boroughs of Hackney and the City. This paper provides an account of how this new model for the National Health Service (NHS) developed in the context of psychotherapy provision within the NHS, within the national and local context in the UK and gives an overview of some the service's key features and how it differs from other services operating in primary and secondary care. A linked paper, in this journal, explores the reality within which the service functions and describes clinical outcomes, health economic data, the modifications to the original model and prospects for the future.     

The fluttering-heart illusion: a new hypothesis

The fluttering-heart illusion is a perceived lagging behind of a colour target on a background of a different colour when the two are oscillated together. It has been proposed that the illusion is caused by a differential in the perceptual latencies of different colours (Helmholtz 1867/1962), a differential in rod-cone latencies (von Kries 1896) and rod-cone interactions (von Grünau 1975, 1976 Vision Research 15 431-436, 437-440; 16 397-401; see list of references there). The purpose of this experiment was to assess the hypothesis that the fluttering-heart illusion is caused by a differential in the perceived velocities of chromatic and achromatic motion. To evaluate this hypothesis, we tested observers possessing normal colour vision and deuteranopes. The perceived delay of a chromatic target relative to an achromatic target was measured as a function of background cone contrast and target colour. For observers with normal colour vision, the perceived delay of the chromatic target is greater in the L-S than the L-M testing conditions. The reverse is observed in deuteranope observers. We suggest that this is caused by the absence of an L-M opponent mechanism contributing to chromatic motion in deuteranopes. Greater background cone contrasts tended to yield smaller perceived delays in both normal and deuteranope observers, indicating that greater chromatic modulation decreases the perceived delay of the colour target. These results support the hypothesis that the fluttering-heart illusion can be explained by a differential in the perceived velocities of chromatic and achromatic motion.     

The vertical-horizontal illusion in a visually-rich environment

In the vertical-horizontal illusion the vertical dimension of a figure typically appears longer than the horizontal. Although there is a large body of research literature on this illusion, all of it refers to simple figures with well-drawn lines, exhibited against plain backgrounds. Our experiment has investigated the illusion using real-world objects in a visually-rich environment. Ten male and 10 female Ss were asked to judge the heights of 10 objects of various sizes and shapes. They made their estimates by having the experimenter mark off a horizontal distance that corresponded to the judged height of the object. Each S estimated the height of each object once a day for three consecutive days. The results show that, by and large, the illusion can be demonstrated for real objects in a visually-rich environment. There was, however,considerable variation among the objects. It appears that estimates of this kind may be influenced by size, size constancy, anchor effects, and angle of regard, along with other, as yet, unidentified factors.     

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.     

Relationships between assessment and treatment within a behavioral perspective

Three alternative strategies to link assessment and treatment within a behavioral perspective are described. First is the functional analysis in which the maintaining variables of the target behavior are identified in assessment and modified in treatment. Although this strategy appears to be frequently successful based on positive treatment outcome, critical tests are seldom done: hypothesized functional analyses are not tested prior to intervention; nor is treatment outcome based on one functional analysis pitted against treatment outcome based on an alternative functional analysis. The second strategy is the keystone target behavior strategy. From among multiple possible target behaviors, one is selected for intervention that produces therapeutic response covariation. The third strategy is the diagnostic strategy. A treatment is selected for a particular client based on its overall success in treating a particular disorder. Empirical comparisons are needed to evaluate the effectiveness of these different strategies, linking assessment and treatment for different disorders.Portions of this paper were presented as invited addresses at the meetings of the Association for Advancement of Behavior Therapy, Philadelphia, November 1984, and of the American Psychological Association, Washington, DC, August 1986.     

Loneliness within a nomological net: An evolutionary perspective

Loneliness is characterized by feelings of social pain and isolation and has both heritable and unshared environmental underpinnings. An evolutionary theory of loneliness is outlined, and four studies replicate and extend prior research on the characteristics of lonely individuals. Studies 1 and 2 indicate that loneliness and depressed affect are related but separable constructs. Study 3 confirms that lonely, relative to nonlonely, young adults are higher in anxiety, anger, negative mood, and fear of negative evaluation, and lower in optimism, social skills, social support, positive mood, surgency, emotional stability, conscientiousness, agreeableness, shyness, and sociability. The set of six personality factors associated with loneliness (surgency, emotional stability, agreeableness, conscientiousness, shyness, and sociability) do not explain the associations between loneliness and negative mood, anxiety, anger, optimism (pessimism), self-esteem, and social support, as each association remained statistically significant even after statistically controlling for these personality factors. Study 4 used hypnosis to experimentally manipulate loneliness to determine whether there were associated changes in the participants’ personality and socioemotional characteristics. Results confirmed that loneliness can influence the participants’ personality ratings and socioemotional states.     

The vista paradox: a natural visual illusion

Suppose an observer views a distant object through a window in the far wall of a room or corridor--a visual scene constituting a vista. If the observer moves toward the window, then the distant object will shrink in apparent size and appear farther away. These effects are paradoxical, because the distant object appears smaller as its visual angle increases. The vista paradox occurs under many other real-world conditions, such as viewing a distant object while moving out of the mouth of a valley, or driving across a topographic crest. In the present study, framing effects and the equidistance tendency are considered as possible factors. However, an explanation based on the dynamic relationship between the visual angle of the framing portion of a vista and the visual angle of a distant object appears more promising.     

Cutaneous saltation within and across arms: a new measure of the saltation illusion in somatosensation

A new objective procedure was used to measure the strength of cutaneous saltation, in order to clarify current debates about the nature of this illusion. Three taps were presented successively to three possible forearm locations. Participants attended to the middle location and reported whether a tap was perceived there. When all stimuli were delivered to the same arm and intertap intervals were short, participants were unable to distinguish real and illusory stimuli at the middle location. When both arms were stimulated, location judgments on one arm were shifted toward a tap subsequently delivered to the other arm. These results challenge the view that saltation is a purely attentional phenomenon, but they are inconsistent with the idea that this illusion is produced in the primary somatosensory cortex.     

Depressive symptoms and use of perspective taking within a communicative context

Objective: The ability to take the perspective of one's conversational partner is essential for successful communication. We assessed whether individuals who report high levels of depressive symptoms have more difficulty with navigating this interpersonal task. Method: Undergraduate students participated in a computerised communication task that, on some trials, required perspective taking (N=125). Results: When participants were grouped according to their self-reported depressive symptoms, the “dysphoric group” (BDI ≥ 16, n=37) showed more errors than a “non-dysphoric group” (BDI ≤ 10, n=56) on trials requiring participants to use the perspective of the speaker, but not on control trials where perspective taking was not required. The dysphoric group demonstrated slower response times overall. Conclusions: Individuals with moderate to high levels of depressive symptoms are more challenged by using a speaker's perspective to interpret statements.