Decision time and movement time in depression: differential effects of practice before and after clinical improvement

Choice reaction time involves, at least two components of response latency, decision time and movement time. Studies of choice reaction time usually provide values of these two components averaged over a given number of trials. The aim of the present study of depressed subjects was to investigate changes across practice on Decision Time (DT) and Movement Time (MT) before and after clinical improvement. 19 depressed subjects were given two sessions of 50 trials each, one before treatment (Di) and one after recovery (Df). Decision time and movement time exhibited quite different patterns. Decision time significantly decreased with clinical improvement. No significant variation across trials was found, in either session. Movement time values varied across trials but the variations observed on Di and Df were significantly different, whereas before treatment latencies recorded at the end of the session were greater than those scored at the start, the contrary was observed after clinical recovery. No significant difference was found between values of movement time scored at the start of the two sessions.     

On the logic of causally necessary and sufficient conditions: Towards a theory of motive-explanations of human actions

Research carried out under the auspices of the Bank of Sweden. Tercentenary Foundation project RJ 86/183: Basic Concepts of Procedural Law in the Light of Present-Day Philosophy of Language and Linguistics.     

Reading long words embedded in sentences: informativeness of word halves affects eye movements

The possibility was explored that the informativeness of a specific region within a word can influence eye movements during reading. In Experiment 1, words containing identifying information either toward the beginning or toward the end were displayed asymmetrically around the point of fixation so that the reader was initially presented with either the informative or noninformative zone. Words were read with shorter summed initial fixation time when the reading was started from the informative zone. In Experiments 2 and 3, the target words were presented in sentences that were to be comprehended. More attention was given to the informative endings of words than to redundant endings. The latter were also skipped more often. The duration of the first fixation was not affected by information distribution within the word, whereas the second fixation duration was. The results of these experiments lend good support to the hypothesis of immediate lexical control over fixation behavior and to the notion of a convenient viewing position.     

Age differences in source forgetting: effects on reality monitoring and on eyewitness testimony

Age differences in memory for the source of memories were investigated using two different experimental paradigms. Experiment 1 used a reality monitoring paradigm. A series of actions were either performed, imagined, or watched, and subjects were later tested for their ability to recognize the actions and identify their origins. Elderly subjects made more false positive responses than did young subjects, and they made more source confusion errors, attributing actions to the wrong sources. Both new and imagined actions were most often misclassified as watched. Experiment 2 used an eyewitness testimony paradigm. After watching a film, subjects read a written version of the story. A recognition test showed that elderly subjects were more often misled by false information in the story than were the younger subjects, and were more confident that their erroneous responses were correct. The findings suggest that a decline in memory for sources may diminish the accuracy of elderly witnesses.     

Effects of uncertainty on melodic

In three experiments, musically trained and untrained adults listened to three repetitions of a 5-note melodic sequence followed by a final melody with either the same tune as those preceding it or differing in one position by one semitone. In Experiment 1, ability to recognize the final sequence was examined as a function of redundancy at the levels of musical structurein a sequence, contour complexity of transpositions in a trial, and trial context in a session. Within a sequence, tones were related as the major or augmented triad; within a trial, the four sequences began on successively higher notes (simple macrocontour) or on randomly selected notes (complex macrocontour); and within a session, trials were either blocked (all major or all augmented) or mixed (major and augmented randomly selected). Performance was superior for major melodies, for systematic transpositions within a trial (simple macrocontours), for blocked trials, and for musically trained listeners. In Experiment 2, we examined further the effect of macrocontour. Performance on simple macrocontours exceeded that on complex, and excluded the possibility that repetition of the 20-note sequences provided the entire benefit of systematic transposition in Experiment 1. The effect of musical structure (major/augmented) was also replicated. In Experiment 3, listeners provided structure ratings of ascending 20-note sequences fromExperiment 2. Ratings onsame trials were higher than those on correspondingdifferent trials, in contrast to performance scores for augmentedsame anddifferent trials in previous experiments. The concept of functional uncertainty was proposed to account for recognition difficulties on augmented same trials. The significant effects of redundancy on all the levels examined confirm the utility of the information-processing framework for thestudy of melodic sequence perception.     

Aggressive behavior inhibition by serotonin and quipazine injected into the amygdala in the rat

The effects on aggressive behavior, open-field activity, and pain threshold of bilateral microinjections of serotonin (20 micrograms) and quipazine (20 micrograms), the direct serotonergic receptor agonist, into the cortico-medial amygdala were investigated in Wistar rats. Both drugs significantly prolonged the attack latency in isolated killer rats (predatory aggression model), and suppressed the incidence of aggressive postures/attacks in shock-induced fighting test (affective aggression). The only difference in the open-field behavior was the lower number of central square entries in drug-treated compared to saline-injected rats. None of the substances produced any significant change in jump threshold. It is concluded that stimulation of serotonin receptors within the amygdala produces inhibition of affective and muricidal behavior in isolated rats. The effect does not seem to be dependent on changes in general activity and pain sensitivity.