An event-coder for evoked potential studies

A device is described which has 10 input and 2 output lines. Grounding an input causes a pulse with a specific amplitude, polarity, and duration to appear on one of the output lines. Pulse parameters can be set by front-panel controls. Thus, 10 distinct events can be coded by associating a unique pulse with each event. These pulses can be recorded on one (or two) channels of a magnetic tape recorder for subsequent processing. The use of this coder in the study of event-related potentials is described.     

Tables of event sequences for sequential analyses of data in psychological experiments containing two-class events

Tables of sequences of two-class events are presented for use in programming psychological experiments in which behavior on trial n may be a function of the events of trials n ? 1, n ? 2, and/or n ? 3. Various factors related to schedule generation are discussed, i.e., restrictions on trial-block length which accompany sequential balance, interrelationships of trial blocks in the multiblock experiment, relationships between run length and r-tuple occurrences, and alternation behavior. Following a consideration of various methods of schedule generation for the two-class experiment, it was concluded that no method can result in schedules that possess all properties considered desirable in psychological experiments. However, the present sequences allow for sequential balance and analysis, and thus should prove useful in producing schedules in some contexts that are standard with regard to sequential influences.     

Non-interaction of ventromedial and lateral hypothalamic mechanisms in the regulation of feeding and hoarding behaviour in the rat

Lesions of the hypothalamic ventromedial nucleus (VMN) led to an immediate increase in food intake but not to any increase in hoarding activity. Later, when subjects were very obese, they failed to hoard even in response to a 16-hr. deprivation schedule, although this schedule did produce hoarding if body weights were held at, or were brought down to, preoperative levels. These results indicate that the lateral hypothalamic mechanism responsible for hoarding and feeding responds to long-term nutritional factors, and that it is not directly affected by the short-term satiety mechanisms in the VMN. These findings support the hypothesis (a) that even “non-physiological” activities (e.g. hoarding, exploration) are motivated by physiological needs, and (b) that the reason these activities do not ordinarily covary with physiological drives is that, unlike the physiological drives, they are not subject to inhibition by the hypothalamic satiety mechanisms.     

The role of response processes in the formation of cross-modality assimilation effects

A unimanual, two-digit choice-reaction-time task was used in conjunction with visual signals presented in the extreme peripheral field. The position of the signal on the retina, the eye stimulated, the hand used in responding, and the operating digits were all controlled for their effects. Stimulus-response compatibility was maintained throughout. It was found that RT to ipsilateral S-R pathways was consistently faster than when the pathways involved transcommissural connections. Subsidiary findings related to differences between the operating digits and the side of signal occurrence. These effects are discussed in connection with known interhemispheric phenomena and other CRT findings.     

Redistributing control between the elements of a compound stimulus

Twenty-eight pigeons were given discrimination training. Four groups were run in which for 0, 2, 4 and 9 sessions of training colour was an irrelevant cue and tone was relevant. Generalization tests were given in extinction; the training colour (C₁) and another colour (C₂) were presented with tone (T) and noise (N). Responding to these four stimulus combinations, TC₁, TC₂, NC₁ and NC₂, allowed the assessment of control by colour and tone. A reduction of control by colour and an increase in control by tone were found to be positively related to the amount of training with colour irrelevant. Tests showed a strong inverse relationship between control by colour and tone.     

Interaction of fear effects with habit strength

Four groups of rats received 0, 3, 6 or 9 days of overtraining after having reached stable performance on a continuous reinforcement bar pressing schedule. Half the subjects in each group had previously been designated emotionally reactive or non-reactive in terms of defecation rates in an open-field test. Following training, there were four test days in which bar pressing in each group was examined in the presence or absence of white noise. The major findings were that, in both the reactive and non-reactive groups, white noise produced a fear reaction which significantly depressed bar pressing at low levels of habit strength while having an energizing effect at higher levels. The results were interpreted as supporting Bardach's (1960) hypothesis that anxiety introduced early in practice is more disruptive than when introduced late in practice.