This new approach to the theoretical understanding of perceptual defense is in contrast to the outmoded understanding of perception presented in Eriksen’s review. The “old” view of Eriksen involved

1. A unidirectional flow of information in the sequence of Stimulus>Perception>Thoughts and Associates>Response, and

2. A formal distinction between “Perception” and “Response”.

In more modern conceptions of the perceptual process, there is no longer a formal distinction between Perception and Response (i.e., the firing of a retinal rod is clearly a response that occurs in the perceptual process). In addition, the “New Look” of information processing involves the complex activity of many interacting systems that exist between “Stimulus” and “Response”. The information processing model holds that human beings have a limited capacity to process the nearly unlimited amounts of information that are available. Processes of perception (like selective attention) choose those pieces of information which have high priority and process them into conscious awareness. Since not everything can be processed, information of low priority is not processed. In addition, there may be negative biases (ex., perceptual defense) against processing certain kinds of information. Imagine that you are watching a very violent movie and it upsets you. The music starts to play and you know that the 6th ax murder will be soon. You don’t want to see it, and you close your eyes. This is a negative bias against processing available information.

There is selectivity (bias) at many phases of the model. Erdelyi reviews the locations of selectivity and evaluates whether each location can account for perceptual defense/vigilance. AS YOU STUDY THIS IT WILL BE IMPORTANT TO FOCUS ON THE MODEL PRESENTED IN THE FIGURE IN ERDELYI’S ARTICLE. Note that

1. This is a multi system approach.

2. The flow of information is multidirectional.

3. Solid lines indicate the flow of input information. Dashed lines indicate feedback and memory contact (but not necessarily memory transfer) and control commands.

4. Memory contact may disrupt ongoing storage operations.

5. Conscious identification occurs in or near Short term storage (STS).

6. Selectivity (bias) occurs at many points (Erdelyi’s article is addressed at finding those bias points that best correspond to perceptual defense/vigilance.

PERIPHERAL ADJUNCTS

1. Occlusion bias would refer to closing ones eyes to avoid seeing something upsetting.

2. Fixation bias would refer to looking away to avoid seeing something upsetting, or looking directly at something important.

Both peripheral adjuncts are responses to already processed information in anticipation of what is to come. These peripheral adjuncts appear not to account for data in typical PD t-scope task. For example, fixation reaction time is typically 200-250 msec., much longer than the recognition thresholds obtained once fixation has occurred.

RECEPTOR SYSTEMS

3. Pupil size bias ( which varies with the emotionality of material seen) can alter sensitivity to information.

4. Lens accommodation bias can affect focusing on an object.

Erdelyi does not believe that perceptual defense/vigilance occurs at 3 or 4.

AFFERENT SENSORY STORAGE is a very short term storage of the firing of axons and dendrites in specific nerves.

ICONIC STORAGE (admitted difficult to understand without extensive knowledge of information processing models) is a high capacity, but brief duration (millesec. To perhaps 2 sec.) Memory buffer. Replicas of the stimulus fade away in echoic form and are lost unless the information is processed further into the

ENCODING SYSTEM, which involves a process of labeling (encoding) into conscious awareness.

5. Encoding bias involves information selection regarding the transfer of information from iconic storage to

SHORT TERM STORAGE (where conscious awareness occurs). The capacity of STS is 7+2 bits of information with a duration of 15-30 sec. So much information is never transferred from ICONIC storage to STS.

ERDELYI BELIEVES THAT PERCEPTUAL DEFENSE/VIGILANCE OCCURS AT 5!!!

REHEARSAL AND CONSOLIDATION is necessary for information to get from STS to

LONG TERM MEMORY (where some believe information may remain forever).

6. REHEARSAL bias involves both positive biases to rehearse and negative biases against rehearsal.

7. OUTPUT bias would be positive or negative (like response suppression) biases to display the response to the information received.

Different kinds of encoding bias may “explain” perceptual defense. For example, a “partial encoding of the cues, “part cue”, or meaning “part meaning” of the information may occur and disrupt further processing of the complete information. Rejected material is quickly lost. Erdelyi believes that this is possible, but he prefers another possibility:

Iconic storage is completely analyzed by the cognitive control processes in Long Term Memory for semantic meaning. On the basis of pos. Or neg. Biases towards the content, corresponding encoding biases may be instituted. Materials not transferred to STM are permanently lost and never become conscious (Perceptual defense). Materials of highest priority are transferred first into conscious (perceptual vigilance). Thus Erdelyi believes that there is full semantic identification of the contents of the icon prior to conscious perception. Essentially, Long Term Memory serves as a filter deciding what passes through and what is blocked from STS.