Outline forms as visual stimuli in psychological experiments

Summary A set of stimuli to be used in psychological experiments is presented. Drawn spontaneously by the Ss, these stimuli are outline forms which can be freely reproduced in an experimental situation. The complexity and meaning-fulness of 100 forms were investigated. Meaningfulness depended on two variables: the probability of a given form having a certain meaning for a S, and the homogeneity of the meanings a given number of Ss ascribe to this form. Three types of meaningfulness could be distinguished: forms with one meaning only, ambiguous forms and nonsense forms. Complexity, homogeneity and probability of having a meaning are listed for all 100 forms.This research was carried out as part of a doctoral dissertation at the Department of Behavior Science of the Swiss Federal Institute of Technology in Zurich. The author expresses gratitude firstly to his supervisors, Professor H. Fischer and Professor K. Bättig, for their encouragement and criticism throughout the research. Thanks are also due to Professor Klaczko and Dr. H.U. Baumann for their many valuable suggestions, to Laurel Gutmann, Professor A. Flammer and Professor M. Perrez for their many helpful comments on earlier drafts of the paper, and to W.G. Hoffmann and R. Casetti for their further assistance.     

Seeing to hear better: evidence for early audio-visual interactions in speech identification

Lip reading is the ability to partially understand speech by looking at the speaker's lips. It improves the intelligibility of speech in noise when audio-visual perception is compared with audio-only perception. A recent set of experiments showed that seeing the speaker's lips also enhances sensitivity to acoustic information, decreasing the auditory detection threshold of speech embedded in noise [J. Acoust. Soc. Am. 109 (2001) 2272; J. Acoust. Soc. Am. 108 (2000) 1197]. However, detection is different from comprehension, and it remains to be seen whether improved sensitivity also results in an intelligibility gain in audio-visual speech perception. In this work, we use an original paradigm to show that seeing the speaker's lips enables the listener to hear better and hence to understand better. The audio-visual stimuli used here could not be differentiated by lip reading per se since they contained exactly the same lip gesture matched with different compatible speech sounds. Nevertheless, the noise-masked stimuli were more intelligible in the audio-visual condition than in the audio-only condition due to the contribution of visual information to the extraction of acoustic cues. Replacing the lip gesture by a non-speech visual input with exactly the same time course, providing the same temporal cues for extraction, removed the intelligibility benefit. This early contribution to audio-visual speech identification is discussed in relationships with recent neurophysiological data on audio-visual perception.     

Remembering the orientation of newly learned characters depends on the associated writing knowledge: a comparison between handwriting and typing

Recent data support the idea that movements play a crucial role in letter representation and suggest that handwriting knowledge contributes to visual recognition of letters. If so, using different motor activities while subjects are learning to write should affect their subsequent recognition performances. In order to test this hypothesis, we trained adult participants to write new characters either by copying them or by typing them on a keyboard. After three weeks of training we ran a series of tests requiring visual processing of the characters' orientation. Tests were ran immediately, one week after, and three weeks after the end of the training period. Results showed that when the characters had been learned by typing, they were more frequently confused with their mirror images than when they had been written by hand. This handwriting advantage did not appear immediately, but mostly three weeks after the end of the training. Our results therefore suggest that the stability of the characters' representation in memory depends on the nature of the motor activity produced during learning.     

Dual Processing of Open- and Closed-Class Words

A series of articles in the past two decades has suggested differential processing of open- and closed-class lexical items by normal adults. Difficulties in replicating a crucial study (Bradley, 1978), however, have weakened the dual route hypothesis. We matched 16 French open-class items to 16 closed-class items for phonological structure, word length, and relative word frequency. Three agrammatic aphasics were asked to read each word in isolation and in a sentence context. Error analysis revealed strikingly more phonological errors on closed-class than open-class items. Dysfluencies were greater on closed-class items and contributed to greater overall reading time for the closed-class words, consistent with a two-route model for the production of closed- and open-class lexical items in Broca's aphasics and, thus, normals.     

Re-emergence of extinguished auditory-cued conditioned fear following a sub-conditioning procedure: effects of hippocampal and prefrontal tetanic stimulations

Post-extinction exposure of rats to a sub-conditioning procedure can evoke conditioned fear, which may correspond to fear return and/or fear learning potentiation. The aim of the present study was to clarify this issue and examine the effects of tetanic stimulation of the hippocampus (HPC) and medial prefrontal cortex (mPFC), two brain regions implicated in post-extinction modulation of conditioned fear. Rats were initially submitted to five tone-shock pairings with either a 0.7-mA or 0.1-mA shock. Tone-evoked freezing was observed only with the higher shock intensity, indicating that the 0.1-mA shock corresponded to a sub-conditioning procedure. All conditioned rats underwent fear extinction with 20 tone-alone trials. When retrained with the sub-conditioning procedure, they displayed again tone-evoked freezing, except when the initial tone was unpaired or a new tone was paired with the 0.1-mA shock, demonstrating fear return rather than fear learning potentiation. We also found that HPC and mPFC tetanic stimulations, applied 24h after the sub-conditioning procedure, similarly reduced this fear return. However, mPFC inactivation abolished temporary HPC tetanus effect, whereas HPC inactivation did not interfere with mPFC tetanus effect. These data confirm our previous findings and reveal the nature of HPC-mPFC interactions in post-extinction modulation of conditioned fear.