The Same-Different task is an experimental paradigm in which a stimulus pair is presented in succession to a participant whose task is to determine if the stimuli are Same or Different. Typical results show that participants tend to be quicker to respond Same then they are to respond Different. Since the 1960s, many models were proposed to explain this effect, but none has yielded conclusive evidence. The objective of this thesis is to test these models with three experiments by focusing on three research questions: 1) what is the source of the effect, the participant or the stimuli?; 2) what is the organization of the cognitive mechanisms underlying the task?; and 3) what is the effect of the number of attributes on the processing capacity? Results show that the fast-same effect stems from the characteristics of the stimuli rather than an inherent preference for sameness. They also show that the cognitive architecture underlying the task is serial, but that it does not seem to explain solely the fast-same effect. Indeed, the fast-same effect seems to be rather caused by a more efficient processing of Same stimuli in the first 500 ms of the treatment compared to Different stimuli.

The Same-Different task has a long and controversial history in cognitive psychology. For over five decades, researchers have had many difficulties modelling the simple task, in which participants must respond as quickly and as accurately as possible whether two stimuli are the “Same” or “Different”. The main difficulty in doing so stems from the fact that “Same” decisions are much faster than can be modelled using a single process model without resorting to post-hoc processes, a finding since coined the fast-same phenomenon. In this thesis, I evaluate the strengths and shortcomings of past modelling endeavours, deconstruct the fast-same phenomenon while exploring the role of priming as its possible mechanism, investigate coactivity as a possible architecture underlying both decision modalities, and present an accumulator model whose assumptions and parameters stem from these results that predicts Same-Different performance (both response times and accuracies) using a single-process, a finding deemed near impossible by Sternberg (1998).

Have you ever heard a song that hasn’t played in years, and immediately recognize it? What cognitive processes determine this, and why does it seemingly happen to everyone? Using the Expectancy Theory of Music (Meyer, 1965) a working explanation for the possibility of why such strange phenomena exists is proposed. Based on expectancy, words and melody are processed together, and sung words are treated as part of the expected whole. In three experiments, memory was tested using same- different task. Each experiments investigates a different level of memory. Taking into account systematic uncertainty and the violation of expectancy when an unexpected appears, these experiments were able to be analyzed and studied in regards to their effects on memory. College students from the Claremont Colleges are to be randomly selected for this experiment. Findings should show a consistent interaction between melody and vocal sequences throughout each experiment.

Darbo tikslas – atskleisti figūrų, pateikiamų vienu metu ir nuosekliai, sukimo mintyse ypatumus naudojant tapatumo įvertinimo užduotį. Tiriamieji (32 studentai) atliko tapatumo vertinimo užduotį, kur jiems vienu metu bei nuosekliai (arba atvirkštine tvarka) buvo pateikiamos vienodų arba skirtingų netaisyklingų daugiakampių poros. Stimulai buvo rodomi 100ms vienalaikio pateikimo atveju, esant nuosekliam pateikimui 50ms ir 50ms. Tiriamieji turėjo atsakyti, ar figūros vienodos (nepaisant pasukimo kampo), ar skirtingos. Buvo matuojamas reakcijos laikas bei teisingų atsakymų skaičius. Nustatyta, kad nepasuktos viena kitos atžvilgiu vienodos figūros atpažįstamos tiksliau bei greičiau nei pasuktos bet kokiu kampu. Tiek vienalaikio, tiek nuoseklaus figūrų pateikimo atveju tiesinė reakcijos laiko priklausomybė nuo figūrų tarpusavio pasukimo kampo nenustatyta. Tiek vienodos, tiek skirtingos figūros nuoseklaus pateikimo atveju atpažįstamos tiksliau nei vienalaikio, o reakcijos laikas, vertinant tiek vienodas, tiek skirtingas figūras, trumpesnis vienalaikio pateikimo atveju nei nuoseklaus. Vyrų ir moterų vienodų figūrų atpažinimo tikslumas nesiskiria, bet vyrų reakcijos laikas trumpesnis nei moterų. / The purpose of this study was to examine mental rotation of simultaneously and successively presented figures. 32 students performed same – different task in which the pairs of the same or different irregular polygons were presented simultaneously and successively or vice versa. Stimuli were presented briefly – for 100 ms when presented simultaneously and 50 ms and 50 ms when presented successively. The subjects had to answer whether the two figures were the same or different. Response time and performance accuracy were recorded. The results of the experiment showed that not rotated figures were identified faster and more accurately than those rotated at any angle. The increase in reaction time as a linear function of the angle of rotation was not found (either under simultaneous presentation or under successive one).The same figures as well as the different ones were identified more accurately when presented successively than simultaneously and the response time was shorter under simultaneous presentation than under successive one. The accuracy of men and women did not differ, but men outperformed women by response time.