Quarterly Journal of Experimental Psychology

The present experiments explored ways in which information encoded along different dimensions might be co-ordinated to determine memory performance. First, can an acoustic similarity decrement be offset by additional semantic encoding? Experiment I offers evidence for this compensatory interaction of codes. Second, does trade-off occur such that more information held in one code means less in another code? Third, are codes additive? Experiment II offers no support for the notion of a trade-off between encoding systems. However, when two codes were made available in the second study, recall was increased over the level achieved by either code alone.

Under the conditions of the distractor paradigm, short-term retention declines to a minimum in a very brief period. The rapid forgetting can be said to reflect the declining contribution of the short-term store or primary memory and the asymptote can be taken as a measure of the contribution of the long-term store or secondary memory. It was shown that manipulating proactive effects by varying the recency of prior material affected only the primary memory component of the short-term retention function. On the other hand manipulating the difficulty of the subsidiary task performed during the retention period with proactive effects held constant affected both the primary and the secondary components. The results were discussed with respect to the relation between the two memory components and the idea that proactive effects are limited to long-term store.

Recognition accuracy in a tachistoscopic identification task typically declines as the size of the set from which the target was selected increases. To determine whether this effect is due to selective encoding from iconic store, a masking stimulus, intended to erase the icon, was presented following the stimulus. Information about the set was then presented. It was found that subjects' performance in this post-cueing situation did not differ from performance in a pre-cueing condition, where the set was presented prior to the stimulus. It was concluded that set size does not have its effect through selective encoding from iconic store. Results were discussed in terms of the fragment theory.

It was confirmed that highly reliable “over-shooting“ (O-SH) and “undershooting” (U-SH) can be obtained when a stimulus associated with a contrasting magnitude of reward intrudes briefly into a session in which the animal receives either a high or low magnitude of reward as a baseline condition (Baltzer and Weiskrantz, 1970). These effects may be related to Crespi “elation” and “depression” effects, but it is also possible that they are dependent on differences in the amount of food ingested on the two baseline conditions. The effects of variations in body weight and pre-feeding in the rat were examined. The optimal level for obtaining the effects lies around the 95% body weight level. With body weight held constant, alterations in short-term satiation induced by pre-feeding before all sessions did not significantly change the magnitude of intrusion effects except in one extreme instance that might be accounted for by a basement effect. Differences in satiation level between the two baseline conditions can affect powerfully the magnitude of O-SH and U-SH, but nevertheless when such differences are eliminated reliable effects are still found. Arguments are advanced as to how short-term satiation and long-term deprivation factors might account for the magnitude of O-SH and U-SH, and reasons offered for considering that O-SH and U-SH have an emotional basis.

In three separate experiments an attempt was made to demonstrate global stereopsis in two rhesus monkeys by using random dot stereograms projected and viewed through polarizing filters. Although both animals learned a number of discriminations, control tests showed that both were perceiving non-depth cues such as monocular identification of minute pattern differences or brightness differences caused by reflections of polarized light. In a final experiment red/green anaglyph forms of the stereograms were viewed through red/green filters. Both monkeys, together with a third experimentally naive animal, showed incontrovertible evidence of prompt discrimination based on stereopsis. This paper makes a number of recommendations about the use of random dot stereograms to demonstrate global stereopsis in animals.

Repeating temporal patterns were presented in the auditory and visual modalities so that: (a) all elements were of equal intensity and were equally spaced in time (uniform presentation); (b) the intensity of one element was increased (accent presentation); or (c) the interval between two elements was increased (pause presentation). Intensity and interval patterning serve to segment the element sequence into repeating patterns.

For uniform presentation, pattern organization was by pattern structure, with auditory identification being faster. For pause presentation, organization was by the pauses; both auditory and visual identification were twice as fast as for uniform presentation. For auditory accent presentation, organization was by pattern structure and identification was slower than for uniform presentation. In contrast, the organization of visual accent presentation was by accents and identification was faster than for uniform presentation. These results suggest that complex stimuli, in which elements are patterned along more than one sensory dimension, are perceptually unique and therefore their identification rests on the nature of each modality.

Recently nerve compression block as a method of investigating movement control without kinaesthetic feedback has been questioned on the grounds that motor impairment (as measured by nerve conduction parameters) is a confounding factor. In order to clarify the relationship between sensory and motor function, behavioural data was obtained on both at systematic time intervals throughout the duration of the block. The findings indicated that significant decrements in tapping measures occurred somewhat earlier in the time course of the block than decreases in kinaesthetic discrimination. Also, contrary to assumption, the majority of subjects ceased to perform prior to total kinaesthetic loss. The data suggest that motor impairment is a “crucial” issue (Laszlo, 1966) in the use of this technique, and provide further behavioural support for the neurological findings of Kelso, Stelmach and Wanamaker (1974).