Global visual completion of quasi-regular shapes

The topic of amodal completion has often been investigated by using partly occluded shapes that are regular. In research that has typically been done with displays such as these regular shapes, it has been shown that global aspects of a shape can determine completion. To see how robust these global influences in the completion process are, we investigated quasi-regular shapes, ie shapes with a certain overall regularity but not based on metrical identities. First, in experiment 1 participants had to complete quasi-regular shapes in a drawing task. Then, in experiment 2 the primed-matching paradigm was used. Results from both experiments provided evidence for global completions. In experiment 3 we found that multiple global completions can be primed, which, as a control experiment showed, cannot be explained by some inability of the visual system to see the difference between the different completions. These data support the notion that global influences on visual occlusion are apparent even when the partly occluded stimulus is outside the domain of regular shapes. Implications for a global approach are provided.     

Factors contributing to the implicit dynamic quality of static abstract designs

Participants rated the dynamic quality of a set of twelve-element nonrepresentational or abstract visual designs each composed of one of four types of triangles or four types of quadrilaterals. We investigated the contribution to the perceived or implicit dynamics of the design of the four factors edge alignment of compositional elements, physical weight distribution about the horizontal axis, activity directions within the designs, and type of compositional element. It was found that edge alignment of elements was the most influential factor contributing to the dynamics both of triangle and of quadrilateral designs. In addition, dynamics was found to be positively correlated with the number of perceived activity directions within both types of stimuli. Triangle designs, but not quadrilateral ones, with greater structural weight above the horizontal axis were rated as more dynamic. Results suggest that implicit dynamics of nonrepresentational designs arises from a percept based on a global spatial analysis of the stimulus characteristics studied.     

When timing the mind one should also mind the timing: biases in the measurement of voluntary actions

Trevena and Miller (2002, this issue) provide further evidence that readiness potentials occur in the brain prior to the time that participants claim to have initiated a voluntary movement, a contention originally forwarded by Libet, Gleason, Wright, and Pearl (1983). In their examination of this issue, though, aspects of their data lead them to question whether their measurement of the initiation of a voluntary movement was accurate. The current article addresses this concern by providing a direct analysis of biases in this task. This was done by asking participants to make subjective timing decisions regarding a stimulus that could be measured objectively. Our findings suggest that their timing task was indeed biased such that participants' tend to report events as happening approximately 70 ms later than they actually happened. Implications for the original Libet et al. claims are discussed.     

Physical,neural, and mental timing

The conclusions drawn by Benjamin Libet from his work with colleagues on the timing of somatosensorial conscious experiences has met with a lot of praise and criticism. In this issue we find three examples of the latter. Here I attempt to place the divide between the two opponent camps in a broader perspective by analyzing the question of the relation between physical timing, neural timing, and experiential (mental) timing. The nervous system does a sophisticated job of recombining and recoding messages from the sensorial surfaces and if these processes are slighted in a theory, it might become necessary to postulate weird operations, including subjective back-referral. Neuroscientifically inspired theories are of necessity still based on guesses, extrapolations, and philosophically dubious manners of speech. They often assume some neural correlate of consciousness (NCC) as a part of the nervous system that transforms neural activity in reportable experiences. The majority of neuroscientists appear to assume that the NCC can compare and bind activity patterns only if they arrive simultaneously at the NCC. This leads to a search for synchrony or to theories in terms of the compensation of differences in neural delays (latencies). This is the main dimension of the Libet discussion. Examples from vision research, such as "temporal-binding-by-synchrony" and the "flash-lag" effect, are then used to illustrate these reasoning patterns in more detail. Alternatively one could assume symbolic representations of time and space (symbolic "tags") that are not coded in their own dimension (not time in time and space in space). Unless such tags are multiplexed with the quality message (tickle, color, or motion), one gets a binding problem for tags. One of the hidden aspects of the discussion between Libet and opponents appears to be the following. Is the NCC smarter than the rest of the nervous system, so that it can solve the problems of local sign (e.g., "where is the event"?) and timing (e.g., "when did it occur?" and "how long did it last?") on its own, or are these pieces of information coded symbolically early on in the system? A supersmart NCC appears to be the assumption of Libet's camp (which includes Descartes, but also mystics). The wish to distribute the smartness evenly across all stages of processing in the nervous system (smart recodings) appears to motivate the opponents. I argue that there are reasons to side with the latter group.     

A computational account of altered error processing in older age: Dopamine and the error-related negativity

When participants commit errors or receive feedback signaling that they have made an error, a negative brain potential is elicited. According to Holroyd and Coles’s (in press) neurocomputational model of error processing, this error-related negativity (ERN) is elicited when the brain first detects that the consequences of an action are worse than expected. To study age-related changes in error processing, we obtained performance and ERN measures of younger and high-functioning older adults. Experiment 1 demonstrated reduced ERN amplitudes in older adults in the context of otherwise intact brain potentials. This result could not be attributed to uncertainty about the required response in older adults. Experiment 2 revealed impaired performance and reduced response- and feedback-related ERNs of older adults in a probabilistic learning task. These age changes could be simulated by manipulation of a single parameter of the neurocomputational model, this manipulation corresponding to weakened phasic activity of the mesencephalic dopamine system.     

Measuring differences in preactivation on the Internet: the content category superiority effect

Preactivation of particular content categories in memory yields latency differences in a visual recognition task. Two Internet studies demonstrate this content category superiority effect (CCSE). Target words are repeatedly flashed for 400 ms and then masked for 200 ms. Experiment 1 shows that differences in pre-activated memory content, related to participants' use of computer operating systems, influence z-scored visual word recognition latencies. Experiment 2 shows that this influence is susceptible to instruction. Participants expecting to find positive words recognized those words faster, whereas participants expecting to find negative words were faster on negative words. The CCSE provides a basis on which new measures of implicit memory content can be founded. Two such applications are discussed--the Motive Superiority Measure of implicit motives, and a latency-based measure of self-focused attention.     

Phonological sensitivity and the acquisition of new words in children

Two studies are reported which aimed to examine the relationship between phonological sensitivity and the acquisition of new words that systematically differed in the familiarity of their sound structures. In the first study measures of phonological sensitivity, phonological short-term memory, vocabulary, and nonverbal ability were administered to forty-one 5-year-old children. Phonological sensitivity was related to the paired-associate learning of phonologically unfamiliar words, but not to the learning of familiar words. In the second study a group of 14 nonreading 5-year-old children received phonological sensitivity training. A control group was trained in semantic categorization. After the training, the phonological sensitivity group did perform better on measures of letter knowledge and phonological sensitivity (rhyme and first-sound categorization) and appeared to learn phonologically unfamiliar words more easily. The findings of both studies suggest that phonological sensitivity can support the acquisition of novel words.     

A sociohistorical view of group psychotherapy in the United States: the ideology of individualism and self-liberation

A deep strain of individualism permeates American culture, rooted in the political-economic ideology of capitalism. The ideal of a self-governing individual is promoted, independent from social, historical, and cultural forces, whose thoughts and emotions are located within the construct of a masterful self, ready to be filled and expanded. This article traces the influence of self-liberatory ideology in American group psychotherapy through the religious revivalist and Mental Hygiene movements. The "progressivism" of pioneering group theorists is examined in terms of revisionist psychology and self-liberatory practice. Psychodrama and T-groups are demonstrated to be precursors to the encounter group movement in which the belief in self-liberation reached its zenith. Early group analytic approaches are seen to eschew transpersonal and group dynamic processes.     

Tamara Dembo's European years: working with Lewin and Buytendijk

In this paper early work of the American rehabilitation psychologist Tamara Dembo (1902-1993) is brought to light. She was highly influenced by the concepts of Kurt Lewin's topological psychology, and she used the framework of topological psychology to analyze her investigations on animal behavior carried out with the Dutch zoopsychologist Frederik J. J. Buytendijk. These investigations have so far been ignored and are being described for the first time making use of archival materials.