Grasping spheres,not planets

Memory for objects helps us to determine how we can most effectively and appropriately interact with them. This suggests a tightly coupled interplay between action and background knowledge. Three experiments demonstrate that grasping circumference can be affected by the size of a visual stimulus (Experiment 1), whether that stimulus appears to be graspable (Experiment 2), and the presence of a label that renders that object ungraspable (Experiment 3). The results are taken to inform theories on conceptual representation and the functional distinction that has been drawn between the visual systems for perception and action.     

VOLITIONAL ASPECTS OF VOICE PERFORMANCE: AN EXPERIMENTAL APPROACH

The subjects (all females) were instructed to hold a certain note. In some of the trials an alien (female) voice with a continuously falling or rising frequency unexpectedly replaced the subject's own voice as the auditory stimulus in her headphone. Most of the subjects took the alien voice as their own and experienced a complete lack of volitional control over their own voice. A compensatory behaviour was found; when the subjects tried to hold the note the frequency of their voices went in the opposite direction to the frequency of the alien voice.     

The use of control groups in artificial grammar learning

Experimenters assume that participants of an experimental group have learned an artificial grammar if they classify test items with significantly higher accuracy than does a control group without training. The validity of such a comparison, however, depends on an additivity assumption: Learning is superimposed on the action of non-specific variables—for example, repetitions of letters, which modulate the performance of the experimental group and the control group to the same extent. In two experiments we were able to show that this additivity assumption does not hold. Grammaticality classifications in control groups without training (Experiments 1 and 2) depended on non-specific features. There were no such biases in the experimental groups. Control groups with training on randomized strings (Experiment 2) showed fewer biases than did control groups without training. Furthermore, we reanalysed published research and demonstrated that earlier experiments using control groups without training had produced similar biases in control group performances, bolstering the finding that using control groups without training is methodologically unsound.     

The feeling of fluent perception: a single experience from multiple asynchronous sources

Zeki and co-workers recently proposed that perception can best be described as locally distributed, asynchronous processes that each create a kind of microconsciousness, which condense into an experienced percept. The present article is aimed at extending this theory to metacognitive feelings. We present evidence that perceptual fluency-the subjective feeling of ease during perceptual processing-is based on speed of processing at different stages of the perceptual process. Specifically, detection of briefly presented stimuli was influenced by figure-ground contrast, but not by symmetry (Experiment 1) or the font (Experiment 2) of the stimuli. Conversely, discrimination of these stimuli was influenced by whether they were symmetric (Experiment 1) and by the font they were presented in (Experiment 2), but not by figure-ground contrast. Both tasks however were related with the subjective experience of fluency (Experiments 1 and 2). We conclude that subjective fluency is the conscious phenomenal correlate of different processing stages in visual perception.     

On estimating the difference limen in duration discrimination tasks: a comparison of the 2AFC and the reminder task

This article assesses whether the two-alternative forced-choice (2AFC) and the reminder tasks (i.e., method of constant stimuli) yield identical estimates of the difference limen (DL). In a series of six experiments, participants discriminated between two duration stimuli. Experiments 1-5 employed auditory stimuli, and Experiment 6 employed visual stimuli. Experiments 1 and 2 combined each of the two tasks with an adaptive and a nonadaptive procedure for threshold estimation. Experiment 3 varied the distribution of the comparison levels, whereas Experiment 4 employed random interstimulus intervals. Experiments 5 and 6 examined the influence of the presentation order of the standard and comparison stimuli. Results indicate that both the adaptive and the nonadaptive procedures yield virtually identical DL estimates; yet, the 2AFC task produces consistently larger DLs than does the reminder task. In addition, DL increases when the standard occurs in the second rather than in the first stimulus position. In order to account for these results, we assume that participants use an internal standard instead of the actually presented standard as a reference for their judgment.     

Self, Other, Positive, and Negative Affect Scales of the Self-Confrontation Method: factorial structure and unidimensionality

In the self-confrontation method, the rows of a grid consist of valuations (i.e. summaries of important personal narratives), while the columns contain affects grouped into four scales (see title). These affects (varying from 16 to 30) are rated on a 0–5 scale of intensity, resulting in an affect profile for each valuation. Principal components analysis on the affect profiles of a client sample, using a list of 30 affects, yielded a 3-factor solution, with 2 unipolar and 1 bipolar factor, in accordance with the four scales. On the basis of this analysis, a list of 24 affects was derived with six affects per scale. This list was then applied to a student sample to cross-validate the results. Unidimensionality of the four scales was found at the level of single grids, and across both client and student samples. It was concluded that the four scales of the 24-affect list appeared to be psychometrically sound and optimally suited for use in research and practice.     

Processing two tasks with varying task order: central stage duration influences central processing order

In a recent study, Sigman and Dehaene (2006, PLoS Biology, 4, 1227–1238) reported that perceptual processing duration influences processing order of two tasks in the psychological refractory period paradigm (PRP). The present study examines whether the duration of central processes also influences processing order. For this purpose, we employed letter tasks with different central processing durations and varied task order in the PRP. In one part of the experiment, a tone discrimination task was combined with a similar time-consuming letter discrimination task. In the other part, the tone task was combined with a more time-consuming letter task, which required a mental rotation of the letter thereby prolonging central processing. If the duration of central processes influences processing order, participants should perform the tone task first more often when it is presented with the more time-consuming mental rotation task, than when it is presented with the similar time-consuming letter task. The results clearly confirm this prediction and thus show that not only perceptual processing duration but also central processing duration affects processing order in a dual-task situation. We suggest that the reported effect mirrors a tendency of participants to minimize total reaction time to both tasks by reducing slack time.     

Exogenous visual attention prolongs perceived duration

Previous studies have shown that spatial attention prolongs the perceived duration of visual stimuli. Chen and O'Neill (Perception & Psychophysics, 63, 1229-1238, 2001) reported, however, the reversed result and thus challenged the generality of this attention effect. We therefore reinvestigated the influence of spatial attention on the perceived duration of visual stimuli in various experimental settings. In five experiments, perceived duration was longer for validly cued stimuli; thus, spatial attention was found to prolong perceived duration. In a further experiment, the specific conditions were such that neither the attention effect nor the reversed pattern, as found by Chen and O'Neill, emerged. Although we cannot provide a conclusive account of why Chen and O'Neill observed the reversed attention effect, the present results reinforce the generality of the spatial attention effect on perceived duration but also make advisable a systematic examination of the factors that might modulate this effect.