Automatic Encoding Of Unattended Items In Visual-short-term Memory

The human visual system can concentrate on the most task-related information through selective attention, and this helps to maximize the use of the limited cognitive resource. The process of selective attention is going with suppressing the distractions, but there is evidence indicating that the unattended items can get processed in a certain way. These evidences mainly base on the fact that the performance of the current task can be influenced by the existence of the unattended items, speeding up or slowing down the time needed for the task, and mostly without consciousness. However, most of the studies focus on describing the effect of the unattended information on perception, ignoring their possible form of existence in the visual-short-term memory(VSM). Some of the critical questions on this are:Can unattended items have their concrete form in the VSM memory, not merely in form of an unseen one interfering current tasks? Whether their concrete form can be retrieved if existed? How would the representations change through time?The present research tried to answer these questions. In experiment1, the independent variable was the angle between the attended bar and the unattended bar, while the dependent variable was the angle between the perceived attended bar and the actual attended bar. In details, the colored squares were to be attended items first, while the black bars that appeared at the same time with the colored squares but in different positions were unattended items. When the colored squares disappeared, the subject should shift their attention to where the unattended items once showed. At this time point, the unattended items had disappeared for a certain time(1.4s), and then some light-grayed bars would flash in the corresponding positions.In half of the trials, one of the flashed bars need to be recalled after a position cue has been showed. Because the light-colored bars were sometimes so faint that it was hard for the subject to perceive, the subject may tend to confuse the ill-perceived items with the unattended items showed before if the unattended ones had been kept in the VSM. The result of the experiment showed, compared with the control group, that the orientation of the attended bars recalled by the subject biased to the orientations of the unattended bars significantly(a=0.05). This implies that the orientation of the unattended bar has received certain processing and has been kept in VSM. In experiment2, the accuracy of the unattended items in the VSM has been studied. Bars would be distributed in different positions at the same time. Some of the bars need to be attended, others to be neglected. There are two kind of time period for keeping bars in mind before test. Result showed that the degree of accuracy for the attended items is higher than the unattended ones, and for both, declining with time, but the unattended item fade more quickly than the attended ones(a=0.05). The recalling precision for the attended items has not been affected by the existing of the unattended ones. The individual differences are obvious in their recalling performance and the recalling precision for attended items and unattended ones tend to have positive correlation(p=0.056).The main conclusion of the research are:1. The unattended items can get into the VSM in concrete form and be retrieved in certain conditions.2. The unattended items seem to intrude into VSM, but the attention system can choose what to be kept in VSM.3. It seems that a mechanism irrelevant to attention is one of the factors that determine the capacity of VSM.