Linguistic encoding in short-term memory as a function of stimulus type

In this study, we investigated bases for encoding linguistic stimuli in short-term memory. Past research has provided evidence for both phonological (sound-based) and cherological (sign-based) encoding, the former typically found with hearing subjects and the latter with deaf users of sign language. In the present experiment, encoding capabilities were delineated from encoding preferences, using 58 subjects comprising six groups differing in hearing ability and linguistic experience. Phonologically related, cherologically related, and control lists were presented orally, manually, or through both modalities simultaneously. Recall performance indicated that individuals encode flexibly, the code actually used being biased by incoming stimulus characteristics. Subjects with both sign and speech experience recalled simultaneous presentations better than ones presented orally or manually alone, which reveals the occurrence of enhanced encoding as a function of linguistic experience. Total linguistic experience appeared to determine recall accuracy following different types of encoding, rather than determining the encoding basis used.     

Recognition and recall by children and adults as a function of variations in memory encoding instructions

In four experiments Ss were instructed to learn a set of 40 words by producing implicit associative responses to each item (association instructions), by repeating items over and over (repetition instruction), or by using their own devices (neutral instructions). Experiment I showed that recognition memory (RM) accuracy was greatest under association instructions for adults and children and least under repetition instructions for children. The implications of these results for a frequency theory analysis for RM were discussed. Experiments II, III, and IV examined free recall (FR) as a function of encoding instructions at short (1 min) and long (either 90 min or 24 h) retention intervals. FR was worst under repetition instructions, with little overall difference between the association and neutral conditions. However, in Experiments III and IV, using school children, the neutral condition exceeded the others in FR after 90 min but not after 1 min.     

Recognition memory performance as a function of reported subjective awareness

Three experiments introduced a recognition memory paradigm designed to investigate reported subjective awareness during retrieval. At study, in Experiments 1A and 2, words were either generated or read (generation), while modality of presentation (auditory versus visual) was manipulated in Experiment 1B. Word pairs (old/new or new/new) were presented during test trials, and participants indicated if they contained an old word by responding "remember", "know" or "new" in Experiments 1A and 1B, and by responding "strong no", "weak no", "weak yes", or "strong yes" in Experiment 2. Participants were then required to decide which of the 2 words was old. We demonstrated that the proportion measures used in the Remember Know paradigm substantially underestimated the influence of generation on familiarity resulting in an artificial dissociation between indices of knowing (familiarity) and remembering (recollection). We also found a qualitatively different pattern of forced-choice recognition performance as a function of claimed awareness.     

Numerosity estimation as a function of stimulus organization.

It was proposed that stimulus organization of a set of homogeneous items can best be measured by using the mean distance to nearest neighbours. Patterns of dots were generated that fell on four different positions along the cluster continuum, from highly regular, through random, to clustered. When thirty subjects were asked to judge numerosity, their estimates decreased significantly as cluster measures increased. Four possible interpretations of the effect of organization on numerosity perception are discussed.     

Intentional and incidental visual memory as a function of cognitive level and color of the stimulus

Performance of two groups of youngsters, educable mentally retarded (CA 15-5; MA 11-4; IQ 74.3) and those of average ability (CA 10-5; MA 11-3; IQ 109.1) was compared for intentional and incidental visual memory as a function of cognitive level and color of the stimulus. Nonretarded subjects performed significantly better than the retarded ones of equal MA. Both groups performed better with a color than black-white card, and both groups did better on the tasks involving intentional rather than incidental memory.     

Recognition memory for pitch of fixed and roving stimulus tones

The method of delayed comparison was used to measure pitch memory under two conditions of presentation, either the same standard tone on every trial (fixed S) or one of four equally likely standard tones (roving S), six durations of interference interval ranging from 0.0 to 4.0 sec, and two types of interference interval, either blank or filled with a pure tone. Listeners were instructed not to rehearse the S tone during the interference interval. For both fixed-S and roving-S conditions, accuracy of performance, as measured by area under the ROC curve, declined as interval duration increased and declined more rapidly following an interference-filled than following a blank interval. In general, forgetting proceeded at a slower rate under fixed-S conditions than under roving-S conditions. A second experiment showed that very little forgetting is obtained over 4 sec for roving-S conditions if instructions permit rehearsal of the S tone and suggests that the conclusions from the first experiment be restricted to nonrehearsal instructional conditions.     

The manipulation of stimulus quality and the definition of stimulus encoding operations in memory scanning experiments

Two experiments examine procedures for defining and isolating stimulus encoding processes within the standard memory scanning task. Two manipulations are used to converge on this definition: letter case (i.e., physical vs. name matching of letters) and stimulus quality. Experiment 1 produced equal scanning rates for the name match and the control conditions in which letter case was not varied. The physical match conditions produced scanning rates half as great as the control. None of these rates were greatly affected by the degradation (contrast reduction) of the probe stimulus, although the small difference in rates for the physical match condition was significant. Experiment 2 investigated two modes of stimulus degradation, contrast reduction and the addition of visual noise. All of the results of the first experiment were replicated for both modes of degradation, with the exception of the change in the scanning rates for the physical match condition. In addition, visual noise produced greater differences between positive and negative response times than did contrast reduction, which did not differ from the high contrast control condition. These results indicate that an abstract internal code is derived during the encoding of the probe stimulus from which the effects of stimulus quality have been removed. Thus, factors that interact with stimulus quality in memory scanning tasks can be assumed to have a locus within the encoding stage of processing.     

The stimulus suffix effect as a memory coding phenomenon

Two short-term memory experiments examined the nature of the stimulus suffix effect on auditory linguistic and nonlinguistic stimulus lists. In Experiment 1, where subjects recalled eight-item digit lists, it was found that a silently articulated digit suffix had the same effect on recall for the last list item as a spoken digit suffix. In Experiment 2, subjects recalled lists of sounds made by inanimate objects either by listing the names of the objects or by ordering a set of drawings of the objects. Auditory suffixes, either another object sound or the spoken name of an object, produced a suffix effect under both recall conditions, but a visually presented picture also produced a suffix effect when subjects recalled using pictures. The results were most adequately explained by a levels-of-processing memory coding hypothesis.     

The effects of emotion and encoding strategy on associative memory

Research has demonstrated that when discrete pieces of information are integrated together at encoding-imagining two items together as a single entity, for example-there is a mnemonic benefit for their relationship. A separate body of literature has indicated that the presence of emotional information can have an impact on the binding of associated neutral details, in some cases facilitating associative binding (MacKay et al. Memory and Cognition 32:474-488, 2004; Mather, Perspectives on Psychological Science 2:33-52, 2007), and in other cases impeding the processing of associated details (Easterbrook, Psychological Review 66:183-201, 1959; Kensinger, Emotion Review 1:99-113, 2009). In the present experiments, we investigated how memory for neutral words is affected by the emotionality of the information with which they are presented (whether with an emotional word or a second neutral word) and the encoding context (integrated or nonintegrated strategy). Participants viewed word pairs and were instructed to visualize the items as an integrated unit or to visualize them separately from one another. The results of Experiment 1 showed a disproportionate mnemonic benefit for neutral items that were integrated with other neutral items over those integrated with emotional items. The results of Experiments 2A and 2B showed that this effect interacted with encoding time: When given 2?s to encode, participants showed no effect of integration on memory for neutral-neutral pairs, but showed a significant mnemonic benefit for integrating emotional-neutral pairs. When given 4 or 6?s, the integrative benefit increased significantly for neutral-neutral pairs but decreased for emotional-neutral pairs. These results suggest that creating an integrated mental image of two neutral items requires a more time-consuming process than integrating an emotional and a neutral item, but that extra effort may result in a downstream mnemonic benefit.     

Hue discrimination as a function of stimulus luminance

The relation between hue discrimination and stimulus luminance was investigated. It was found that discrimination was best at the highest luminance and deteriorated at the lowest, except in the yellow region.     

Recognition memory for pictorial stimuli: biasing effects of stimulus emotionality

The possibility that stimulus emotionality might influence recognition bias in a long-term memory task was studied with respect to both the valence and arousal dimensions of emotion. For this purpose, we used 108 International Affective Picture System pictures that were representative of all regions of this two-dimensional space. Signal detection theory analysis was applied using A'and B' D as discrimination and bias measures, respectively. In general, the results showed that greater discrimination was accompanied by a response bias that was more conservative for pleasant and for unarousing pictures than for unpleasant and for arousing ones. These results provide new evidence in connection with the emotion-induced recognition bias in long-term memory performance.     

Effects of encoding strategy on long-term memory for odours

The effects of various encoding tasks on long-term recognition of odours were examined. Different groups of subjects were instructed (a) to form visual images of the source of the odour, (b) to generate the name of the odour and provide a dictionary-like definition, or (c) to describe a life episode of which the odour reminded them. A no-strategy control was simply told to try to remember the odours for a subsequent recognition test. One week later, subjects performed a yes-no recognition test for the odours. The second and third groups displayed significantly higher recognition than the controls. The visual imagery group did not differ significantly from the control group. The results seem to be accounted for best by dual coding theory.