Introduction: The method of constant stimuli means that threshold is determined by presenting the observer with a set of stimuli of which some are above the threshold and of which some are below the threshold but that the set of stimuli are presented in a random order.
Name of the experiment: Weight Discrimination
Purpose: To determine differential threshold (DL) of the weights with the help of constant stimuli
Details of the subject:
- Gender ……………..
Material used: Weight Box, blind fold, random table, metronome, paper and pen ( weight discrimination )
Preliminary setup: First of all the random table for presentation of the stimuli for the ten trials was
made ensuring that each weight has equal probability of being selected and also that same weights don’t occur on the same serial position. This is done for 10 trials. Two observation tables were prepared, one for randomised presentation of variable stimulus (Sv) to be paired with standard stimulus (Ss) for ten
trials and another for noting the responses of the subject.
Procedure: The subject was called to the lab and seated comfortably. A rapport was established during which her details were sought. Thereafter she was instructed as follows- “I will be putting a blindfold on your eyes. Thereafter I will be putting a weight on your palm which would be followed by another weight. You have to tell me whether the second weight is heavier, equal or lighter than the first weight. Be very careful in giving your judgements.”
The subject was blindfolded and was given the weight for two second with the help of the metronome with the gap of two seconds between the presentation of the Ss and Sv. For first five trials the standard stimulus (Ss) is presented first followed by the variable stimulus (Sv) and for the last five trials the Sv is presented first and Ss follows. For the responses heavier a sign of plus (+); for lighter a sign of minus (-); and for equal a sign of equal(=) was written in the observation table. Responses thus obtained were put in the observation table which was prepared serially for the twelve weights. Thereafter the frequency table and the proportion table for heavier, equal and lighter responses were prepared. After this, the upper limen, lower limen , DL, IU AND PSE were calculated.
- Results of all calculations for weight discrimination
- have to be showed in tables for weight discrimination
- Presentations of heavier for weight discrimination
- lighter and equal responses along with DL have to be represented in the graph.
Points to ponder:
Guilford, J.P. (1954) – Psychometric
Methods, Tata McGraw-Hill Publishing.
Woodworth, R.S. & Schlosberg, H.(1938).
Experimental Psychology, Oxford & I B H Publishing
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