![]() An old-new recognition memory test was adopted and the test was completed within a period of about a minute from the beginning of the study phase. The number of pictures displayed at study (the list length) was limited to less than 10, affording close to perfect performance at the longest exposures used. The range of temporal exposures that were investigated in this project, from a few milliseconds to a few seconds, is representative of the normal range of durations of ocular fixations ( Harris, Hainline, Abramov, Lemerise & et al., 1988). The present study is concerned with the effects of exposure time, repetition, spacing and lag on memory for generic visual scenes, such as those normally encountered in everyday life by exploring the visual environment. However, later studies ( Cepeda, Pashler, Vul, Wixted & Rohrer, 2006) have disputed such simple dependence of memory strength on total study time and have provided evidence for super-additive, facilitatory effects: it has been shown that under appropriate conditions there is greater improvement when repeated items are spaced (separated in time by intervening items or interruptions) rather than massed (the Spacing Effect), and that performance may improve further as a function of temporal distance between repetitions (the Lag Effect). Consider the Law of Practice: early studies showed that repeated exposure to an item over two separate epochs each lasting a time T affords the same memory performance as exposure to the same item over a single epoch lasting a time 2T ( Bugelski, 1962, Cooper & Pantle, 1967), suggesting that total exposure time completely predicts memory strength (the Total Time Hypothesis). While these psychological “laws” of memory may seem evident even from casual observations, scientific investigations of temporal aspects of memory function, ongoing since the classical studies of Ebbinghaus ( Ebbinghaus, 1964), have provided a more nuanced view of the influence of time and practice on various aspects of memory performance ( Roediger, 2008). Repeating the material to be remembered and/or studying it for a longer time increases the probability of correctly recalling it at a later epoch (the Law of Practice) and quality of recall declines with the passage of time since last study (the Law of Recency). It is common knowledge that memory depends on time and practice. The main conclusion is that the growth of visual scene familiarity with temporal exposure and repetition is a stochastically independent process. The data are consistent with an Unequal Variance Signal Detection Theory model of memory that assumes the average strength and the variance of the familiarity of pictures both increase with total study time. In the experimental conditions of the present study we find no evidence of either facilitatory or inhibitory effects: recognition memory for pictures in RSVP supports the Total Time Hypothesis. However, other studies have disputed such simple dependence of memory strength on total study time, demonstrating superadditive facilitatory effects of spacing and lag, as well as inhibitory effects, such as the Ranschburg effect, Repetition Blindness and the Attentional Blink. Early memory studies with verbal material found that knowledge of total exposure time at study is sufficient to accurately predict memory performance at test (the Total Time Hypothesis), irrespective of number of repetitions, spacing or lag. The present study is concerned with the effects of exposure time, repetition, spacing and lag on old/new recognition memory for generic visual scenes presented in a RSVP paradigm.
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