Generating Strictly Controlled Stimuli for Figure Recognition Experiments

This protocol can be used to generate strictly controlled and objectively defined stimuli for figure recognition experiments. Using a 16 figure database, you can select a stimulus figures that satisfy prescribed values of structure and superficial geometric properties. The experimental environment consists of a liquid crystal display monitor, and a response button box connected to a computer.

There are three buttons on the box labeled Enter, F6, and F5.By pressing the Enter button, the current screen will proceed to the consecutive screen. The F6 button is for responses using the index finger, and the F5 button is for responses using the middle finger. To enable the examination of various hypotheses that concern the criticality of a certain feature in the recognition of figures in a fairly objective manner, insert a floppy disk into the floppy disc unit connected to the computer, that will be used for the stimulus preparation, and open the pair generation program.

Then use the keyboard to input a random number as an initial value for the random number generation function, and input either one or two using the keyboard, as the digital specifier. To prepare a stimulus set for a participant, sequentially write a presentation number, digital state, pair type with a tag, number of line segments, and four pairs of vertex labels in the line specification format of the left and right figures of each trial to the floppy disk unit, simultaneously echoing these values on the screen. After obtaining written, informed consent from the participant, show sample figure pairs to demonstrate to the participant how they will be asked to decide whether a presented pair of figures is identical in shape, regardless of their orientations, as quickly and accurately as possible.

When the participant is ready, start the stimulus presentation program on the computer for experiments, and click Identity Decision Task and Participant Information, to enter the participant's name, sex, and age. When all of the information has been entered, click End of Specification and Read Stimulus. Then select the PRBLM2.

DAT file in the floppy disk drive and click Open on the file specification screen. Next, seat the participant in front of the monitor, with their head on the chin rest, and confirm a 60 centimeter distance from the participant's forehead to the monitor. Then click Execution to start the experiment.

If the instruction screen shows the digital state one, instruct the participant to press the F6 key with the index finger when the figures are the same, and to press the F5 key with the middle finger when the figures are different. After the digital state has been determined, have the participant press Enter once on the response box, and then once again in response to the Ready prompt on the screen, to start the trial. Upon the presentation of a pair of practice pairs on the stimulus screen, have the participant press the F6 or F5 key as soon as a decision is reached.

If the response was correct, the decision was correct will appear on the feedback message screen. If the response was incorrect, the decision was erroneous will appear on the screen. After reading the feedback message, have the participant press enter to proceed and respond to the next prompt screen.

When all of the practice trials are complete, start of the test trials will appear. Have the participant begin the trial using the same response buttons as used for the practice trials. In this representative experiment, the error and latency rates were significantly different across the pair types, with exception of the difference in latency between the asymmetric and non-identical zero pairs.

The error rates and latency data both suggest that the non identical 0.73 and one pairs are easily discriminable compared with asymmetric pairs. However, the nearly absent difference in latency between the non-identical zero pairs, and the asymmetric pairs, strongly suggests the the sameness of the line lengths caused the asymmetric pairs to be more difficult to discriminate. It is important to select geometrically appropriate figure pairs with the use of the database, and ad-hoc creations, according to your research questions.

If you appropriately select figures with specific feature values, you can examine the criticality of individual features during the figure recognition tests.