The psychophysics of iconic storage

Some simple models of iconic storage, based on the persisting responses of photoreceptors, were tested in two experiments. Substantial changes in such physical parameters as adapting luminance, stimulus luminance, and stimulus contrast produced little or no change in the duration of partial-report performance. This is at odds with most receptoral models. It seems unlikely that any model based on receptoral persistence can accommodate the results, thus forcing one to locate the icon beyond the receptors and probably beyond the retina as a whole.     

Semantic specificity in cued recall

In three cued recall experiments, extralist retrieval cues that were congruous in meaning to an encoded target pair of words produced better recall of the targets than wh6n the cuetarget relation was incongruous. However, this result, which differs from that of other experiments, depended in some cases on scoring recall of a target pair when either member of the pair was recalled. It is argued that (1) pairs of words are typically stored as higher order units, (2) the best test procedure is to request recall of both members of the pair when an extralist cue is presented, and (3) semantic features provide an important dimension in the mnemonic representation of word events.     

The training of community mental health clinicians as infant specialists

This article describes the training program and collaborative effort between the Department of Mental Health, the Child Development Project at the University of Michigan, and community mental health agencies. The in-service training is described with special attention to content and process, including the role of case supervision. The effect of the training program as a catalyst to service development is noted.     

Straightness as a cue for luminance edge interpretation

In order to determine the reflectance of a surface, it is necessary to discount luminance changes produced by illumination variation, a process that requires the visual system to respond differently to luminance changes that are due to illumination and reflectance. It is known that various cues can be used in this process. By measuring the strength of lightness illusions, we find evidence that straightness is, used as a cue: When a boundary is straight rather than curved, it has a greater tendency to be discounted, as if it were an illumination edge. The strongest illusions occur when a boundary has high contrast and has multiple X-junctions that preserve a consistent contrast ratio.     

The perceptual buildup of three-dimensional structure from motion

We present a set of psychophysical experiments that measure the accuracy of perceived three-dimensional (3-D) structure derived from relative motion in the changing two-dimensional image. The experiments are motivated in part by a computational model proposed by Ullman (1984), called the incremental rigidity scheme, in which an accurate 3-D structure is built up incrementally, by considering images of moving objects over an extended time period. Our main conclusions are: First, the human visual system can derive an accurate model of the relative depths of moving points, even in the presence of noise in their image positions; second, the accuracy of the 3-D model improves with time, eventually reaching a plateau; and third, the 3-D structure currently perceived appears to depend on previous 3-D models. Through computer simulations, we relate the results of our psychophysical experiments with the predictions of Ullman's model.     

Beyond junctions: nonlocal form constraints on motion interpretation

Because of the aperture problem, local motion measurements must be combined across space. However, not all motions should be combined. Some arise from distinct objects and should be segregated, and some are due to occlusion and should be discounted because they are spurious. Humans have little difficulty ignoring spurious motions at occlusions and correctly integrating object motion, and are evidently making use of form information to do so. There is a large body of theoretical and empirical evidence supporting the importance of form processes involving junctions in the way motion is integrated. To assess the role of more complex form analysis, we manipulated nonlocal form cues that could be varied independently of local junctions. Using variants on diamond and plaid stimuli used in previous studies, we found that manipulations distant from the junctions themselves could cause large changes in motion interpretation. Nonlocal information often overrides the integration decisions that would be expected from local cues. The mechanisms implicated appear to involve surface segmentation, amodal completion, and depth ordering.     

Problem solving and the development of abstract categories in programming languages

The question of how novice and expert computer programmers represent and use programming concepts is addressed here. Lines of programming code forming three complete programs were presented one at a time and in random order in a multitrial free recall procedure. Qualitative and quantitative measures revealed clear but different subjective organization in the two groups. The novices used a syntax-based organization, whereas the experts used a more abstract hierarchical organization based on principles of program function.     

Psychological science and analogical reminding in the design of artifacts

In this article, we discuss two approaches to design currently prevalent in the field of human- computer interaction. Proponents of one approach advocate working from first principles of psychological science; practitioners of the second, engineering, approach find that successful design is often the result of analogical discovery. However, these approaches have not yet been evaluated for the usability of their methods. Can designers work in each of these ways? What are the difficulties? How can they be overcome? In this paper, we take a first step in addressing these questions. We analyze the form in which principle-based design poses its questions, thereby uncovering some of the difficulty that is encountered in this way of working. Furthermore, we analyze the form in which engineering problems are expressed and identify an advantage of this typically analogical way of working. We then suggest a way in which analogy-based design can supplement both principle-based and empirically driven design.     

Adventures with gelatinous ellipses--constraints on models of human motion analysis

An ellipse rotating rigidly about its center may appear to rotate rigidly or to deform nonrigidly so that it appears gelatinous. We use this ambiguous stimulus to study how motion information is propagated across space. We find that features that are quite far from the contour of the ellipse may have a strong influence on the percept of the ellipse, provided they move in a way consistent with the motion of the ellipse. We show that the percept cannot be accounted for by computational models that pool constraints over a local area only, or by models that propagate information along contours, or by models that indiscriminately propagate information across space. However, the percept can be accounted for by a class of models that assume smoothness in a layered representation.     

A randomized trial to evaluate the course of effects of a program to prevent adolescent depressive symptoms over 12 months

Although few prevention studies have been designed to investigate the course of prevention effects over time, it seems that the effects on depressive symptoms increase from post-intervention to 6-month follow-up but then decrease with longer lags to follow-up. Furthermore, previous prevention studies have found differential intervention effects for boys and girls without testing possible explanations for this effect. The present randomized control group study with 301 8th-grade students examined the effects of a depression prevention program from baseline until 12-month follow-up. As expected, while positive intervention effects were found on girls’ depressive symptoms, no such effects were found on boys’ depressive symptoms. Further, the positive intervention effects on girls’ depressive symptoms increased to the 6-month follow-up and remained stable through the 12-month follow-up, while depression symptoms in control-group girls increased from 6-month to 12-month follow-up. Further exploratory analyses revealed that neither baseline conduct problems nor cognitive or social knowledge of the prevention program at 12-month follow-up alone explained the sex effect. However, some limited evidence was found indicating that total knowledge (cognitive and social) might partially explain the effect but there was significant variability remaining to be explained.