3, 6, 9, 12, 18か月児の新奇刺激に対する視覚と手操作行動の分析から,次の結果が得られた。 (1)6〜18か月児において,新奇刺激(第1, 4試行)は,短期なじみ刺激や,時間をおいて再呈示したなじみ刺激に比べて,顕著に多くの注視をもたらした。3か月児では,第4試行での注視の増大がみられなかった。 (2)新奇刺激がなじみになる過程の減少量は,後続の新奇刺激への反応量と直接関係せず,特に9か月児において,前者が少ないのに後者が大きかった。 (3)持続時間測度では,6か月児においても新奇刺激への増大という観点で,視覚と手操作との反応の一致がみられた。また潜時の測度では,月齢差も条件差もみられなかった。以上の点で,Schafferらの所見と異なっていた。 (4)3か月児では,1回あたりの注視が長く,1試行に占める注視の%が大きく,手の活動の%が小さかった。6か月児では,1回あたりの注視が短く,注視の%が小さく,手操作の%が大きかった。9〜18か月児では,1回あたりの注視が長く,注視の%が大きく,手操作の%も大きかった。

Visual and manipulative responses to the novel objects were studied in 40, 3-, 6-, 9-, 12-, and 18-month old infants. The stimuli were two novel objects (A, B), and were matched in terms of ease of holding, stimulus complexity, audio-visual feedback potentiality, and similarity to everyday tools. The Ss were assigned to either one of the two stimulus presentation orders: AAABBBAB and BBBAAABA. Termination of each trial was contingent on the S's response, and therefore not determined by a fixed time lapse. With the exception of the 3-month. old infants, initial decrement invisual responsiveness was followed by a significant recovery at the fourth trial when the other novel stimulus was introduced, but not at the seventh or eighth trial when the familiar stimulus was introduced again. The amount of decrement in the short-term familiarization process was not directly related to that of the response for the following novel stimulus. Especially in 9-month-old infants, the former was small and the latter was large. In the infants aged 6 months and older, visual and manipulative responsiveness to novelty was concordant, not supporting Schaffer's findings. And there was the discrepancy in findings by the measures of manipulation: Total manipulation time and Latency to manipulation. The 3-month old infants had longer visual regard per response, larger percentage of looking within one trial and smaller percentage of manual activity within one trial. The 6-month old infants had shorter visual regard, smaller percentage of looking and larger percentage of manipulation. Beginning at 9 months, infants had longer visual regard, larger percentage of looking and manipulation. These findings suggest the transition of relative dominance of vision and manipulation during infancy.