Grasping visual illusions: no evidence for a dissociation between perception and action

Neuropsychological studies prompted the theory that the primate visual system might be organized into two parallel pathways, one for conscious perception and one for guiding action. Supporting evidence in healthy subjects seemed to come from a dissociation in visual illusions: In previous studies, the Ebbinghaus (or Titchener) illusion deceived perceptual judgments of size, but only marginally influenced the size estimates used in grasping. Contrary to those results, the findings from the present study show that there is no difference in the sizes of the perceptual and grasp illusions if the perceptual and grasping tasks are appropriately matched. We show that the differences found previously can be accounted for by a hitherto unknown, nonadditive effect in the illusion. We conclude that the illusion does not provide evidence for the existence of two distinct pathways for perception and action in the visual system.     

The role of inhibition in the regulation of sequential action

We investigated the regulation of sequential action using a new paradigm. Participants learned a sequence of seven stimulus categories and then monitored for them during successive displays. All displays were instances of these categories, presented in pseudorandom order. On each trial, participants monitored for an instance of Category 1, pressed a key on a computer keyboard, then monitored for an instance of Category 2, pressed a key on the keyboard, and so on for all seven categories. Thus, a perfect trial contained exactly seven responses. Intrusion errors were classified as a function of ordinal distance from the current serial position ( n ). Fewer intrusion errors were made at near serial positions than at far ones, suggesting a gradient of lateral inhibition. In addition, more intrusions were made on n + 1 categories than n − 1 categories, suggesting greater availability of intended than completed goals. In accord with current models of sequential action, the results indicate lateral and self-inhibition as important mechanisms in regulation of sequential action.     

Dimensionen der Gefühle

Zusammenfassung Es war das Ziel der Untersuchung, ein System der Gefühlsqualitäten zu finden, das im Unterschied zu früheren Klassifikationsversuchen nicht auf der Anwendung formaler Kategorien oder anderer, gewissermaßen von außen an den Gegenstand herangetragener Gesichtspunkte beruhte, sondern aus den Erlebnisinhalten selbst hervorging.Nach verschiedenen Methoden wurden drei Versuche unternommen, in denen die Versuchspersonen auf Grund der Vergegenwärtigung des Erlebnisses Urteile über die Ähnlichkeit und über bestimmte Eigenschaften von Gefühlsqualitäten abzugeben hatten.Aus den Ergebnissen aller drei Versuche konnten Ordnungssysteme der verwendeten Gefühlsqualitäten gebildet werden. Trotz der Verschiedenheit der angewendeten Methoden besteht zwischen den drei Systemen in den vergleichbaren Punkten eine nahezu vollkommene Übereinstimmung.Die Gesamtheit der Gefühlsqualitäten ordnet sich nach dem Resultat dieser Untersuchung in drei Dimensionen an, denen die Bezeichnungen Angenehm—Unangenehm, Unterwerfung—Überhebung und Grad der Motivierung gegeben wurden.Nach einigen Betrachtungen über die der Beurteilung von Gefühlsqualitäten zugrunde liegenden subjektiven Prozesse werden methodische Folgerungen gezogen, die besagen, daß die Voraussetzungen für die Untersuchung der Gefühle weit günstiger sind, als dies nach der vorherrschenden Meinung der Fall ist. Schließlich wird die Anwendungsmöglichkeit der Resultate auf einige Fragestellungen der Gefühlsforschung an Hand von Beispielen erörtert.     

Intergenerational transmission of marital quality across the transition to parenthood

One of the most frequently reported changes across the transition to parenthood is a decline in marital quality after the birth of a first baby. Experiences in the family of origin may influence the trajectory of marital quality. Our study aimed to investigate the impact of recollections of family-of-origin marriage on marital quality (self-reports and clinical evaluation) from pregnancy to 1 year after the birth of a first child. A total of 62 first-time parents completed questionnaires (self-reported marital satisfaction) and clinical interviews (clinical evaluation of couples' dialogue quality). Although self-reported marital satisfaction and observed dialogue quality were highly associated, only self-reported marital satisfaction declined from pregnancy to 1 year after birth. This decrease was partly due to very high marital satisfaction during pregnancy. Different trajectories for self-reported marital satisfaction and observed dialogue quality were found for participants with recollections of low-, average-, and high-quality family-of-origin marriage. A structural equation model showed that participants who recollected a negative quality in their parents' relationship reported more negative changes in the quality of their own marriages. There seems to be an intergenerational transmission of marital quality that comes to light when couples are challenged by the birth and rearing of a baby.     

Neural correlates of a default response in a delayed go/no-go task

Working memory, the ability to temporarily retain task-relevant information across a delay, is frequently investigated using delayed matching-to-sample (DMTS) or delayed Go/No-Go tasks (DGNG). In DMTS tasks, sample cues instruct the animal which type of response has to be executed at the end of a delay. Typically, performance decreases with increasing delay duration, indicating that working memory fades across a delay. However, no such performance decrease has been found when the sample cues exist of present vs. absent stimuli, suggesting that pigeons do not rely on working memory, but seem to respond by default in those trials. We trained 3 pigeons in a DGNG task and found a similar default response pattern: The diverging slopes of the retention functions on correct Go and No-Go trials suggested that pigeons by default omitted their response following No-Go stimuli, but actively retained task-relevant information across the delay for successful responses on Go trials. We conducted single-cell recordings in the avian nidopallium caudolaterale, a structure comparable to the mammalian prefrontal cortex. On Go trials, many neurons displayed sustained elevated activity during the delay preceding the response, replicating previous findings and suggesting that task-relevant information was neurally represented and maintained across the delay. However, the same units did not show enhanced delay activity preceding correct response suppressions in No-Go trials. This activation-inactivation pattern presumably constitutes a neural correlate of the default response strategy observed in the DGNG task.     

When do irrelevant visual stimuli impair processing of identical targets?

Three experiments investigated whether the repeated-letter inferiority effect (RLIE) and repetition blindness (RB) are identical phenomena or not and how the RLIE can be reconciled with the flanker compatibility effect (FCE). Participants reported a masked target and ignored an unmasked distractor. We manipulated the type of distractor (identical, alternative target, or neutral), the order of presenting distractor and target, and the predictability of target location. When distractors preceded the targets, distractors identical to the target always caused deficits in target processing (i.e., RB). With simultaneous presentation, identical distractors caused deficits (i.e., an RLIE) for unpredictable target locations only. Yet the RLIE was significantly smaller than RB. This result suggests that simultaneously presented stimuli are identified serially, in random order, if target position is unpredictable. As a result, RB arises only in the 50% of all trials with identical distractors in which the distractor is identified before the target. With simultaneous presentation and predictable target location, however, parallel processing of targets and distractors was possible that gave rise to an FCE in recognition accuracy. Analyses of false alarm rates revealed no evidence of significant response biases.     

Action comprehension: deriving spatial and functional relations

A perceived action can be understood only when information about the action carried out and the objects used are taken into account. It was investigated how spatial and functional information contributes to establishing these relations. Participants observed static frames showing a hand wielding an instrument and a potential target object of the action. The 2 elements could either match or mismatch, spatially or functionally. Participants were required to judge only 1 of the 2 relations while ignoring the other. Both irrelevant spatial and functional mismatches affected judgments of the relevant relation. Moreover, the functional relation provided a context for the judgment of the spatial relation but not vice versa. The results are discussed in respect to recent accounts of action understanding.