Harold Schiffman

Frequency of episodic memories as a function of their age

Ninety-eight undergraduates were given a list of 20 common English nouns and told to inspect each word until a specific episodic memory associated with it came to mind, and to write a few words to identify that memory. After finishing the list, they were asked to go back and to date the episodic memories as accurately as they could. The frequency of memories as a function of their age was found to be log log linear, with the frequency inversely related to the age of memory.

The organization of stimuli and sensory neurons

Abstract Complex sensory neurophysological data have been condensed and ordered into highly meaningful forms by a mathematical model. Visual and gustatory data have been analyzed, and in both instances the model accounted for at least 98 per cent of the variance of the experimental data. The analyses show the relationships between neurons and stimuli, as well as the relationships within neurons and stimuli alone. The model itself is quite general and can have wide applications, not restricted to data of this particular type. Furthermore, the analyzed data can be plotted geometrically, thus allowing for a clear visual presentation of the relationships.

Association test antonym-response set

Groups of S s were given 54 Kent-Rosanoff-list words in one of three different orders, with one of two different instructions, and with one of two different test formats. Instructions to give the responses that most people give increased non-antonym popular-response frequencies, particularly when a multiple-choice format was used instead of an open-ended format. When words that frequently elecit antonyms were presented early or were rectangularly distributed through the list, more popular-antonym responses were elicited than when such words were generally late in the list. It was suggested that antonym set reduces conceptual effort.

A two-stage model of brightness

Abstract The mathematics of a two-stage theory for the brightness perception of impulsive functions is developed. The first stage is seen as second differencing of the spatial luminance function as imaged on the retina. The second stage is a reconstructive stage which synthesizes the outcome of the first stage into a form isomorphic with brightness perception. This two-stage process allows for the explanation of illusions concerning the illusory propagation of brightness from points of discontinuity. A computational algorithm was presented and applied to a variety of relevant examples.

Word Association: Variables Affecting Popular-Response Frequency

Normal Ss were given 54 Kent-Rosanoff word-association-test items in one of two different orders; antonym-eliciting items were concentrated either (a) near the beginning or (b) near the end of the list. For each order, testing was administered under three different test conditions: (a) standard free-association instructions, (b) instructions to give the response “most people” would give, and (c) “most people” instructions with a multiple-choice test format. The order starting with antonym-eliciting items elicited more popular antonym responses than did the other order. Popularity-set instructions, particularly with the multiple-choice format, elicited more non-antonym popular responses than did free-association test conditions. With repeated testing, popular antonyms became more frequent. For some sequences of test conditions, there was also an increase in non-antonym popular responses with repeated testing.

Visual Perception and Xerography

An electrostatic copying machine was used to model the perception of simultaneous brightness contrast. Such a model may assist the study of sensory inhibition by permitting the study of complex situations as they are transformed by rules similar to those at work in neural integration.

Galton’s number

Galton posed the following question: What is the number of accessible autobiographical episodes in memory? The answer to this question implicates a number of issues in the psychophysics of time and memory. We had found (Crovitz & Schiffman, 1974) a surprisingly fertile equation (log f = log b –; a log t) relating the number (f) of episodes accessible at any given time (t) ago. We discuss this log-log law of memory; we differentiate it, exposing a form of Weber’s law in the time domain; and we integrate this equation, which allows us to answer Galton’s question and make other empirical predictions.

Timing oscillation in human visual imagery

Following the work of Weber & Castleman (1970), who found a time period of about 500 msec for the successive production in imagery of letters of the alphabet, an imaginal task less cognitive in nature was timed. Twenty-four Ss in a CFF study attempted to match the rate of flicker of a subfusional light in visual imagery. The modal ability for imagining flicker is about 250 msec in period.